The document discusses several key concepts related to temperature and heat:
1. It defines temperature as a measure of the average kinetic energy of molecules, while heat is the total thermal energy within an object.
2. It explains concepts such as specific heat capacity, which is the amount of energy required to raise the temperature of a substance, and latent heat, which is the energy required for phase changes without a change in temperature.
3. It discusses various types of thermometers and temperature scales, and provides examples of calculating heat transfer and temperature change using equations for specific heat, latent heat, and thermal expansion.
This document discusses various topics relating to thermal energy and heat transfer. It begins by explaining that thermal energy is a measure of the average kinetic energy of molecules. It then discusses how temperature changes throughout the day due to the sun warming and cooling the Earth. It also explains how adding or removing heat causes the temperature of objects like a snowman and boiling water to change and reach an equilibrium temperature. The document goes on to define key terms like temperature, heat, specific heat capacity, latent heat, and thermal expansion. It provides examples and equations for calculating heat transfer and energy changes associated with temperature variations. Overall, the document provides a comprehensive overview of thermal energy concepts and quantitative relationships.
This document provides information about measuring the specific heat capacity of substances through an electrical experiment. It defines specific heat capacity as the amount of energy needed to raise 1 kg of a substance by 1 degree Celsius. The key equation discussed is E=mcΔθ, where E is energy, m is mass, c is specific heat capacity, and Δθ is temperature change. The document describes setting up an experiment using an immersion heater and thermometer in a solid block to determine the specific heat capacity of the block by measuring the energy input, mass, and temperature change and plotting graphs to calculate c. It discusses analyzing sources of experimental error in the calculation.
The document discusses heat and thermal equilibrium. It defines key terms like temperature, heat, and thermal contact. It explains that when two objects at different temperatures come into contact, heat is transferred from the hotter object to the cooler one until they reach the same temperature and thermal equilibrium. Examples are given like a wet towel being used to reduce a fever by transferring heat from the body. The document also discusses specific heat capacity and how it relates to how fast an object's temperature changes when heat is gained or lost. Specific heat capacities of different materials are provided.
This document discusses various concepts related to heat, including:
[1] Heat capacity and specific heat capacity, which refer to the amount of heat required to change the temperature of a substance. Specific heat capacity is a material's heat capacity per unit mass.
[2] Latent heat of fusion and vaporization, which is the heat absorbed or released during phase changes between solid, liquid, and gas with no change in temperature.
[3] Methods for determining specific heat capacity experimentally, including the mixture method of transferring heat between substances and the electrical method of applying heat from an electrical source.
An introductory outline of the Physics of Heat. I created this presentation at Curtin Sarawak Malaysia as a basis for Foundation Physics students and others to edit and expand. A Creative Commons Attribution-Share Alike License.
Thermal energy, temperature, and heat are defined. Thermal energy depends on temperature, number of particles, and particle arrangement. Temperature is a measure of how hot or cold something is, while heat is the transfer of thermal energy between systems. Temperature is measured in Kelvin using a thermometer, while heat is measured in Joules using a calorimeter. Systems reach thermal equilibrium when there is no net heat transfer between them. The three laws of thermodynamics are also summarized.
This document discusses heat transfer and the three main methods: conduction, convection, and radiation. Conduction involves the direct contact transfer of heat between objects. Convection involves the transfer of heat by the movement of molecules within a substance from warmer to cooler areas. Radiation involves the transfer of heat through space, such as the sun's rays causing sunburn.
This document contains notes from a Thermal Physics class on various topics:
- Heat flows from hot to cold bodies until thermal equilibrium is reached.
- The Kelvin temperature scale defines absolute zero as 0 K and relates Celsius and Kelvin scales.
- Kinetic theory explains gas properties in terms of molecular motion, assuming molecules are small, hard spheres that collide elastically.
- Internal energy, temperature, heat capacity, phase changes, gas pressure, and the mole concept are defined and related to molecular behavior and properties.
Equations, examples, and questions are provided to illustrate these concepts.
This document discusses various topics relating to thermal energy and heat transfer. It begins by explaining that thermal energy is a measure of the average kinetic energy of molecules. It then discusses how temperature changes throughout the day due to the sun warming and cooling the Earth. It also explains how adding or removing heat causes the temperature of objects like a snowman and boiling water to change and reach an equilibrium temperature. The document goes on to define key terms like temperature, heat, specific heat capacity, latent heat, and thermal expansion. It provides examples and equations for calculating heat transfer and energy changes associated with temperature variations. Overall, the document provides a comprehensive overview of thermal energy concepts and quantitative relationships.
This document provides information about measuring the specific heat capacity of substances through an electrical experiment. It defines specific heat capacity as the amount of energy needed to raise 1 kg of a substance by 1 degree Celsius. The key equation discussed is E=mcΔθ, where E is energy, m is mass, c is specific heat capacity, and Δθ is temperature change. The document describes setting up an experiment using an immersion heater and thermometer in a solid block to determine the specific heat capacity of the block by measuring the energy input, mass, and temperature change and plotting graphs to calculate c. It discusses analyzing sources of experimental error in the calculation.
The document discusses heat and thermal equilibrium. It defines key terms like temperature, heat, and thermal contact. It explains that when two objects at different temperatures come into contact, heat is transferred from the hotter object to the cooler one until they reach the same temperature and thermal equilibrium. Examples are given like a wet towel being used to reduce a fever by transferring heat from the body. The document also discusses specific heat capacity and how it relates to how fast an object's temperature changes when heat is gained or lost. Specific heat capacities of different materials are provided.
This document discusses various concepts related to heat, including:
[1] Heat capacity and specific heat capacity, which refer to the amount of heat required to change the temperature of a substance. Specific heat capacity is a material's heat capacity per unit mass.
[2] Latent heat of fusion and vaporization, which is the heat absorbed or released during phase changes between solid, liquid, and gas with no change in temperature.
[3] Methods for determining specific heat capacity experimentally, including the mixture method of transferring heat between substances and the electrical method of applying heat from an electrical source.
An introductory outline of the Physics of Heat. I created this presentation at Curtin Sarawak Malaysia as a basis for Foundation Physics students and others to edit and expand. A Creative Commons Attribution-Share Alike License.
Thermal energy, temperature, and heat are defined. Thermal energy depends on temperature, number of particles, and particle arrangement. Temperature is a measure of how hot or cold something is, while heat is the transfer of thermal energy between systems. Temperature is measured in Kelvin using a thermometer, while heat is measured in Joules using a calorimeter. Systems reach thermal equilibrium when there is no net heat transfer between them. The three laws of thermodynamics are also summarized.
This document discusses heat transfer and the three main methods: conduction, convection, and radiation. Conduction involves the direct contact transfer of heat between objects. Convection involves the transfer of heat by the movement of molecules within a substance from warmer to cooler areas. Radiation involves the transfer of heat through space, such as the sun's rays causing sunburn.
This document contains notes from a Thermal Physics class on various topics:
- Heat flows from hot to cold bodies until thermal equilibrium is reached.
- The Kelvin temperature scale defines absolute zero as 0 K and relates Celsius and Kelvin scales.
- Kinetic theory explains gas properties in terms of molecular motion, assuming molecules are small, hard spheres that collide elastically.
- Internal energy, temperature, heat capacity, phase changes, gas pressure, and the mole concept are defined and related to molecular behavior and properties.
Equations, examples, and questions are provided to illustrate these concepts.
Heat capacity is the amount of heat needed to raise a system's temperature by one degree, expressed in units of thermal energy per degree. Specific heat capacity is the amount of heat needed to increase the temperature of one kilogram of a substance by one degree, expressed in joules per kg per degree Kelvin. The document provides formulas for heat capacity and specific heat capacity, and gives an example quiz to test understanding of specific heat capacity definitions and calculations involving changes in temperature and heat energy.
This document discusses heat transfer and heat exchangers. It defines key units used in heat transfer such as temperature, heat, and heat capacity. It describes different types of heat including latent heat and methods of heat transfer including conduction, convection, and radiation. Specifically, it explains that heat is transferred through conduction by the movement of free electrons in metals and vibration of atoms/molecules, with the rate of conduction determined by thermal conductivity. It also provides examples of thermal conductivity values for common materials.
1. The document discusses key concepts in heat and thermodynamics including temperature, heat transfer mechanisms, thermal expansion, and phase changes.
2. It provides examples of problems and their solutions involving concepts like specific heat, latent heat, temperature conversions, and heat transfer calculations.
3. The key heat transfer mechanisms of conduction, convection, and radiation are explained through examples of how they apply to insulating houses and minimizing energy costs.
The document provides information about heat and thermal equilibrium:
1. Two objects are in thermal equilibrium when the net heat flow between them is zero, meaning their temperatures are the same and there is no longer a transfer of heat.
2. It explains how a liquid-in-glass thermometer works, with the liquid expanding uniformly based on temperature changes to indicate the temperature.
3. Specific heat capacity and latent heat are introduced, explaining how heat transfer causes temperature changes or phase changes in substances.
This document discusses heat and temperature. It begins by explaining early theories of heat, including the caloric fluid theory which was later disproven. It then discusses sources of heat, both natural like the sun and artificial like chemical reactions. Key terms are defined, like conduction, convection and radiation as methods of heat transfer. Common temperature scales are explained including Celsius, Fahrenheit and Kelvin. Effects of heat like expansion and phase changes are covered. The document concludes with a short quiz to test the reader's understanding.
The document discusses several key concepts related to temperature and heat:
- Temperature is a measure of the average kinetic energy of molecules, while heat is the total thermal energy within an object.
- Thermometers like liquid-in-glass and thermistors are used to measure temperature, while specific heat capacity relates the energy required to change an object's temperature.
- Phase changes from solid to liquid or liquid to gas require additional energy called latent heat, as molecular bonds are broken without changing the temperature.
Chapter v temperature and heat. htm nputi hpptrozi arrozi
1. The document discusses various topics relating to temperature and heat including different temperature scales, heat transfer through conduction, convection and radiation, and phase changes of substances.
2. Formulas are provided to calculate heat, temperature changes, expansion of solids, liquids and gases, and heat transfer through various methods.
3. Problems are included at the end of each section to apply the concepts and formulas covered.
This document discusses concepts related to latent heat and specific heat capacity. It defines specific latent heat as the energy needed to change the state of 1 kg of a substance without a change in temperature. Latent heat of fusion refers to the change from solid to liquid, while latent heat of vaporization refers to the change from liquid to gas. Specific heat capacity is defined as the energy needed to raise the temperature of 1 kg of a substance by 1 degree Kelvin. The document provides examples of calculating energy changes using these concepts and measuring specific heat capacities experimentally.
When two objects at different temperatures are placed in contact, heat flows from the hotter object to the colder object until they reach the same temperature and are in thermal equilibrium. Thermal equilibrium occurs when the net heat flow between the objects is zero, meaning they are the same temperature. A liquid-in-glass thermometer works by having mercury in a bulb expand up a capillary tube when heated; the distance it travels corresponds to temperature scales defined by fixed points like ice and steam. Mercury is suitable for thermometers because it conducts heat well and expands uniformly with temperature.
This document discusses key concepts in thermal physics including heat, temperature, specific heat capacity, and latent heat. It begins by defining heat as a form of energy and temperature as a measurement of how hot or cold something is. It explains that different materials require different amounts of heat to change temperature by the same amount due to differences in specific heat capacity. The document then discusses phase changes and how heat is required for changes of state, like melting and boiling, without a change in temperature due to the absorption of latent heat. It provides examples of calculating specific heat capacity and using the principle of conservation of energy to solve problems involving heat transfer.
The document discusses different forms of energy including kinetic energy, potential energy, thermal energy, and nuclear energy. It explains how kinetic energy depends on an object's mass and velocity, and how potential energy depends on an object's mass, height, and gravitational acceleration. The document also covers energy transformations, calculations of kinetic and potential energy, heat transfer through conduction, convection and radiation, and applications of energy including refrigeration and human thermoregulation.
The document discusses thermal properties of matter, specifically heat capacity and specific heat capacity. It defines heat capacity as the amount of energy needed to change an object's temperature by 1 degree. Specific heat capacity is the amount of energy needed to change 1 kg of a material by 1 degree. Materials have different specific heat capacities because their molecules contain different numbers and masses of atoms. The document also describes methods to determine specific heat capacity, including direct calorimetry of liquids and solids, and the indirect method of mixtures.
This document provides an overview of thermochemistry and key concepts related to heat and energy transfers during chemical and physical processes. It defines important terms like heat, temperature, enthalpy, and heat capacity. It also distinguishes between endothermic and exothermic reactions, and describes heat changes associated with phase changes like melting, vaporization, solidification, and condensation. Specific concepts covered include Hess's law of heat summation, standard heats of formation and reaction, and calculating heat changes using thermochemical data.
The document discusses concepts related to temperature and heat measurement. It explains that temperature is a measure of the average kinetic energy of particles, and rises when heat is added to increase particle motion. It describes common temperature scales like Celsius and Kelvin, and how temperature is measured using properties like expansion. Methods for determining heat transfer and changes of state are also covered, including concepts like heat capacity, latent heat, and phase transitions.
Heat is a form of energy that transfers from one body to another due to a temperature difference. Heat flows from hotter to colder areas. It is measured in units like joules, calories, and kilocalories. Heat comes from natural sources like the sun and earth, and artificial sources like chemical reactions, mechanics, and electricity. Thermal energy is the total kinetic and potential energy in a system, while temperature measures the average kinetic energy of molecules and indicates hotness or coldness. There are various instruments that can measure temperature like thermometers, thermocouples, and liquid crystal strips. Heat transfers through conduction in solids, convection in fluids, and radiation through electromagnetic waves in empty space.
This document contains examples and exercises involving the use of specific heat capacity to calculate changes in temperature of materials when heat is added or removed. It includes 4 examples calculating the final temperature of various materials like iron rods, water, and glass when given the initial temperature, mass, heat added/removed, and specific heat capacities. It then provides context on how specific heat capacities of land and water impact sea and land breezes. Finally, it lists 5 practice exercises for students to calculate temperature changes using specific heat capacity.
This document discusses key concepts about temperature and heat transfer. It defines temperature as a measure of the average kinetic energy of particles. All matter is made of atoms or molecules that are always moving, with higher temperatures corresponding to faster average particle speeds. Thermometers measure temperature based on the property of thermal expansion. Common temperature scales are Celsius, Fahrenheit and Kelvin, with Kelvin being the official SI scale. Heat is the transfer of thermal energy between objects at different temperatures, occurring through conduction, convection or radiation until thermal equilibrium is reached.
This document discusses various topics relating to thermal energy and heat. It begins by explaining that thermal energy is a measure of the average kinetic energy of molecules. It then discusses how temperature changes throughout the day due to the sun warming and cooling the Earth. It also explains how adding or removing heat causes the temperature of objects like a snowman and boiling water to change and reach an equilibrium. The document then defines key terms like temperature, heat, specific heat capacity, latent heat, and different temperature scales and units used to measure heat and thermal energy.
The document discusses various topics relating to thermal energy and heat. It begins by explaining that thermal energy is a measure of the average kinetic energy of molecules. It then discusses how temperature changes throughout the day due to the sun warming and cooling the Earth. It also explains how adding or removing heat can change the temperature of objects like a snowman and boiling water. The document then defines key terms like temperature, heat, specific heat capacity, latent heat, and thermal expansion. It provides examples and equations for calculating heat transfer and temperature change. In summary, the document provides an overview of thermal energy concepts and how heat transfer impacts temperature.
The document discusses various topics relating to thermal energy and heat. It begins by explaining that thermal energy is a measure of the average kinetic energy of molecules. It then discusses how temperature changes throughout the day due to the sun warming and cooling the Earth. It also explains how adding or removing heat can change the temperature of objects like a snowman and boiling water. The document then defines key terms like temperature, heat, specific heat capacity, latent heat, and thermal expansion. It provides examples and equations to calculate changes in thermal energy and temperature. In summary:
The document defines thermal energy and explains how temperature changes due to heating and cooling from the sun. It then discusses temperature changes in examples like a snowman and boiling water
Heat is a form of energy that is transferred between objects in contact with each other or at different temperatures. There are three main mechanisms of heat transfer: conduction, convection, and radiation. Conduction requires physical contact, convection occurs through the motion of fluids, and radiation can occur through empty space. Temperature is a measure of the average kinetic energy of molecular motion and is measured using thermometers on standardized scales like Celsius and Kelvin. The amount of heat required to change the temperature of a substance depends on its specific heat. Architectural design can influence heat transfer through a building's envelope and systems.
Heat capacity is the amount of heat needed to raise a system's temperature by one degree, expressed in units of thermal energy per degree. Specific heat capacity is the amount of heat needed to increase the temperature of one kilogram of a substance by one degree, expressed in joules per kg per degree Kelvin. The document provides formulas for heat capacity and specific heat capacity, and gives an example quiz to test understanding of specific heat capacity definitions and calculations involving changes in temperature and heat energy.
This document discusses heat transfer and heat exchangers. It defines key units used in heat transfer such as temperature, heat, and heat capacity. It describes different types of heat including latent heat and methods of heat transfer including conduction, convection, and radiation. Specifically, it explains that heat is transferred through conduction by the movement of free electrons in metals and vibration of atoms/molecules, with the rate of conduction determined by thermal conductivity. It also provides examples of thermal conductivity values for common materials.
1. The document discusses key concepts in heat and thermodynamics including temperature, heat transfer mechanisms, thermal expansion, and phase changes.
2. It provides examples of problems and their solutions involving concepts like specific heat, latent heat, temperature conversions, and heat transfer calculations.
3. The key heat transfer mechanisms of conduction, convection, and radiation are explained through examples of how they apply to insulating houses and minimizing energy costs.
The document provides information about heat and thermal equilibrium:
1. Two objects are in thermal equilibrium when the net heat flow between them is zero, meaning their temperatures are the same and there is no longer a transfer of heat.
2. It explains how a liquid-in-glass thermometer works, with the liquid expanding uniformly based on temperature changes to indicate the temperature.
3. Specific heat capacity and latent heat are introduced, explaining how heat transfer causes temperature changes or phase changes in substances.
This document discusses heat and temperature. It begins by explaining early theories of heat, including the caloric fluid theory which was later disproven. It then discusses sources of heat, both natural like the sun and artificial like chemical reactions. Key terms are defined, like conduction, convection and radiation as methods of heat transfer. Common temperature scales are explained including Celsius, Fahrenheit and Kelvin. Effects of heat like expansion and phase changes are covered. The document concludes with a short quiz to test the reader's understanding.
The document discusses several key concepts related to temperature and heat:
- Temperature is a measure of the average kinetic energy of molecules, while heat is the total thermal energy within an object.
- Thermometers like liquid-in-glass and thermistors are used to measure temperature, while specific heat capacity relates the energy required to change an object's temperature.
- Phase changes from solid to liquid or liquid to gas require additional energy called latent heat, as molecular bonds are broken without changing the temperature.
Chapter v temperature and heat. htm nputi hpptrozi arrozi
1. The document discusses various topics relating to temperature and heat including different temperature scales, heat transfer through conduction, convection and radiation, and phase changes of substances.
2. Formulas are provided to calculate heat, temperature changes, expansion of solids, liquids and gases, and heat transfer through various methods.
3. Problems are included at the end of each section to apply the concepts and formulas covered.
This document discusses concepts related to latent heat and specific heat capacity. It defines specific latent heat as the energy needed to change the state of 1 kg of a substance without a change in temperature. Latent heat of fusion refers to the change from solid to liquid, while latent heat of vaporization refers to the change from liquid to gas. Specific heat capacity is defined as the energy needed to raise the temperature of 1 kg of a substance by 1 degree Kelvin. The document provides examples of calculating energy changes using these concepts and measuring specific heat capacities experimentally.
When two objects at different temperatures are placed in contact, heat flows from the hotter object to the colder object until they reach the same temperature and are in thermal equilibrium. Thermal equilibrium occurs when the net heat flow between the objects is zero, meaning they are the same temperature. A liquid-in-glass thermometer works by having mercury in a bulb expand up a capillary tube when heated; the distance it travels corresponds to temperature scales defined by fixed points like ice and steam. Mercury is suitable for thermometers because it conducts heat well and expands uniformly with temperature.
This document discusses key concepts in thermal physics including heat, temperature, specific heat capacity, and latent heat. It begins by defining heat as a form of energy and temperature as a measurement of how hot or cold something is. It explains that different materials require different amounts of heat to change temperature by the same amount due to differences in specific heat capacity. The document then discusses phase changes and how heat is required for changes of state, like melting and boiling, without a change in temperature due to the absorption of latent heat. It provides examples of calculating specific heat capacity and using the principle of conservation of energy to solve problems involving heat transfer.
The document discusses different forms of energy including kinetic energy, potential energy, thermal energy, and nuclear energy. It explains how kinetic energy depends on an object's mass and velocity, and how potential energy depends on an object's mass, height, and gravitational acceleration. The document also covers energy transformations, calculations of kinetic and potential energy, heat transfer through conduction, convection and radiation, and applications of energy including refrigeration and human thermoregulation.
The document discusses thermal properties of matter, specifically heat capacity and specific heat capacity. It defines heat capacity as the amount of energy needed to change an object's temperature by 1 degree. Specific heat capacity is the amount of energy needed to change 1 kg of a material by 1 degree. Materials have different specific heat capacities because their molecules contain different numbers and masses of atoms. The document also describes methods to determine specific heat capacity, including direct calorimetry of liquids and solids, and the indirect method of mixtures.
This document provides an overview of thermochemistry and key concepts related to heat and energy transfers during chemical and physical processes. It defines important terms like heat, temperature, enthalpy, and heat capacity. It also distinguishes between endothermic and exothermic reactions, and describes heat changes associated with phase changes like melting, vaporization, solidification, and condensation. Specific concepts covered include Hess's law of heat summation, standard heats of formation and reaction, and calculating heat changes using thermochemical data.
The document discusses concepts related to temperature and heat measurement. It explains that temperature is a measure of the average kinetic energy of particles, and rises when heat is added to increase particle motion. It describes common temperature scales like Celsius and Kelvin, and how temperature is measured using properties like expansion. Methods for determining heat transfer and changes of state are also covered, including concepts like heat capacity, latent heat, and phase transitions.
Heat is a form of energy that transfers from one body to another due to a temperature difference. Heat flows from hotter to colder areas. It is measured in units like joules, calories, and kilocalories. Heat comes from natural sources like the sun and earth, and artificial sources like chemical reactions, mechanics, and electricity. Thermal energy is the total kinetic and potential energy in a system, while temperature measures the average kinetic energy of molecules and indicates hotness or coldness. There are various instruments that can measure temperature like thermometers, thermocouples, and liquid crystal strips. Heat transfers through conduction in solids, convection in fluids, and radiation through electromagnetic waves in empty space.
This document contains examples and exercises involving the use of specific heat capacity to calculate changes in temperature of materials when heat is added or removed. It includes 4 examples calculating the final temperature of various materials like iron rods, water, and glass when given the initial temperature, mass, heat added/removed, and specific heat capacities. It then provides context on how specific heat capacities of land and water impact sea and land breezes. Finally, it lists 5 practice exercises for students to calculate temperature changes using specific heat capacity.
This document discusses key concepts about temperature and heat transfer. It defines temperature as a measure of the average kinetic energy of particles. All matter is made of atoms or molecules that are always moving, with higher temperatures corresponding to faster average particle speeds. Thermometers measure temperature based on the property of thermal expansion. Common temperature scales are Celsius, Fahrenheit and Kelvin, with Kelvin being the official SI scale. Heat is the transfer of thermal energy between objects at different temperatures, occurring through conduction, convection or radiation until thermal equilibrium is reached.
This document discusses various topics relating to thermal energy and heat. It begins by explaining that thermal energy is a measure of the average kinetic energy of molecules. It then discusses how temperature changes throughout the day due to the sun warming and cooling the Earth. It also explains how adding or removing heat causes the temperature of objects like a snowman and boiling water to change and reach an equilibrium. The document then defines key terms like temperature, heat, specific heat capacity, latent heat, and different temperature scales and units used to measure heat and thermal energy.
The document discusses various topics relating to thermal energy and heat. It begins by explaining that thermal energy is a measure of the average kinetic energy of molecules. It then discusses how temperature changes throughout the day due to the sun warming and cooling the Earth. It also explains how adding or removing heat can change the temperature of objects like a snowman and boiling water. The document then defines key terms like temperature, heat, specific heat capacity, latent heat, and thermal expansion. It provides examples and equations for calculating heat transfer and temperature change. In summary, the document provides an overview of thermal energy concepts and how heat transfer impacts temperature.
The document discusses various topics relating to thermal energy and heat. It begins by explaining that thermal energy is a measure of the average kinetic energy of molecules. It then discusses how temperature changes throughout the day due to the sun warming and cooling the Earth. It also explains how adding or removing heat can change the temperature of objects like a snowman and boiling water. The document then defines key terms like temperature, heat, specific heat capacity, latent heat, and thermal expansion. It provides examples and equations to calculate changes in thermal energy and temperature. In summary:
The document defines thermal energy and explains how temperature changes due to heating and cooling from the sun. It then discusses temperature changes in examples like a snowman and boiling water
Heat is a form of energy that is transferred between objects in contact with each other or at different temperatures. There are three main mechanisms of heat transfer: conduction, convection, and radiation. Conduction requires physical contact, convection occurs through the motion of fluids, and radiation can occur through empty space. Temperature is a measure of the average kinetic energy of molecular motion and is measured using thermometers on standardized scales like Celsius and Kelvin. The amount of heat required to change the temperature of a substance depends on its specific heat. Architectural design can influence heat transfer through a building's envelope and systems.
Heat and temperature are often confused but refer to different concepts. Temperature is a measure of the average kinetic energy of molecular motion in a substance, while heat is the transfer of energy between objects due to a temperature difference. Several factors affect heat and temperature, including the movement of molecules. Common temperature scales include Celsius, Fahrenheit and Kelvin, and formulas can be used to convert between them. Proper use of thermometers allows accurate measurement of temperature.
The document discusses various topics related to heat and thermodynamics including:
1) Heat is a form of energy transferred between objects due to a temperature difference, not a substance that flows.
2) The internal energy of a substance is the total energy of all its molecules. Temperature measures average kinetic energy.
3) Specific heat is a property that determines how much heat is required to change an object's temperature.
1. Understand that Energy is exchanged or transformed in all chemical reactions and physical changes of matter. As a basis for understanding this concept: (a) Students know how to describe temperature and heat flow in terms of the motion of molecules (or atoms) and (b) Students know chemical processes can either release (exothermic) or absorb (endothermic) thermal energy.
1. Thermochemistry is the branch of thermodynamics that studies heat changes associated with chemical and physical transformations.
2. Energy can change forms but is never created or destroyed according to the law of conservation of energy.
3. Exothermic reactions release heat to the surroundings, decreasing the system's internal energy and making ΔH negative. Endothermic reactions absorb heat from the surroundings, increasing the system's internal energy and making ΔH positive.
1. Thermochemistry examines energy changes that occur during chemical reactions and changes in state.
2. Energy can be transferred as heat or work. Exothermic processes release heat to the surroundings while endothermic processes absorb heat from the surroundings.
3. The specific heat of a substance depends on its mass and chemical composition and determines how much its temperature changes when heat is added or removed. Water has a high specific heat.
This document discusses the history and theory of heat. It begins by describing the early caloric theory which viewed heat as the flow of a fluid called caloric. It then discusses how the calorie, still used today, was named after this theory. Later sections describe experiments by Rumford and Joule establishing that heat represents the transfer of energy. Specific concepts covered include the mechanical equivalent of heat, distinctions between temperature, heat and internal energy, calculations of specific heat and latent heat, and the three modes of heat transfer - conduction, convection and radiation. Equations for quantifying these concepts are also provided.
The document discusses key concepts in thermodynamics including:
1. Thermal energy and temperature, which is a measure of hotness or coldness.
2. Heat is the transfer of thermal energy between objects of different temperatures.
3. There are various instruments for measuring temperature like thermometers, which use thermal sensors and temperature scales.
4. Materials expand when heated as thermal energy increases, and contract when cooled as thermal energy decreases.
1. Thermal conductivity is a measure of a material's ability to conduct heat. It is defined as the amount of heat conducted through a 1 m^2 area with a 1°C temperature difference over 1 second.
2. Specific heat is the amount of heat required to raise the temperature of 1 kg of a substance by 1°C. Latent heat is the heat absorbed or released during a phase change without changing temperature.
3. Rumford rejected the caloric theory of heat, concluding that heat is a form of energy produced by friction or mechanical work, not a fluid. The mechanical equivalent of heat is the amount of work required to produce 1 calorie of heat.
This document provides information about forms of energy and thermochemistry. It begins by defining energy and describing the main forms: mechanical, chemical, electromagnetic, heat (thermal), and nuclear energy. Kinetic, potential (elastic, chemical, gravitational), chemical, electromagnetic, and thermal energies are then explained in more detail. The document also discusses units of thermal energy, such as calories and joules, and how temperature is measured. Finally, it covers thermochemical equations, including how to determine if a reaction is endothermic or exothermic based on the sign of the enthalpy change (ΔH).
The document discusses heat and thermodynamics, specifically:
1. The first law of thermodynamics states that energy cannot be created or destroyed, only converted from one form to another.
2. The second law states that it is impossible to convert all heat into work, some heat must be wasted.
3. Heat transfer occurs through conduction, convection, or radiation, depending on whether the transfer is through a material, moving fluids, or electromagnetic waves.
The document discusses key concepts in temperature and heat, including:
1. It introduces common temperature scales like Fahrenheit, Celsius, and Kelvin scales. It explains how each scale was developed and their distinguishing features.
2. It discusses concepts like thermal expansion - both linear and volumetric expansion. Linear expansion explains how the length of an object changes with temperature, while volumetric expansion explains how the volume changes.
3. It provides examples of calculating temperature conversions between different scales, as well as examples of using equations of linear and volumetric expansion to solve problems involving changes in length or volume due to temperature changes.
This document summarizes key concepts from a physics lecture on heat:
1) Heat is defined as the flow of energy between two objects due to a difference in temperature. It can cause increases in internal energy and temperature.
2) The specific heat of a material determines how much heat is required to change its temperature.
3) Latent heat is the heat absorbed or released during phase changes without a change in temperature.
4) Placement in ice water can decrease the boiling point of a liquid due to decreased external pressure and increased cooling from latent heat of fusion.
This document summarizes key concepts about heat from a physics lecture:
1) Heat is defined as the flow of energy between two objects due to a temperature difference. It can cause increases in an object's internal energy and temperature.
2) The specific heat of a material determines how much heat is required to change its temperature.
3) Latent heat is the heat absorbed or released during phase changes without a temperature change. For example, melting ice absorbs heat but the temperature remains 0°C.
4) Cooling occurs when heat flows from a warmer object to a cooler one, such as ice melting to cool a drink through latent heat absorption.
This document summarizes key concepts about temperature, heat transfer, and clinical thermometers. It defines common temperature scales (Celsius, Fahrenheit, Kelvin) and concepts like thermal expansion, heat, internal energy, specific heat capacity, phase changes, and latent heat. It describes different methods of heat transfer (conduction, convection, radiation). It outlines direct and indirect types of clinical thermometers, including liquid-in-glass, chemical dot matrix, digital, thermocouple, infrared thermometers and their uses.
This document discusses measurements of thermal energy and heat. It defines thermal energy as the energy relating to heat or caused by heat. Measurement of thermal energy involves indirect measurement of molecular kinetic energy. The factors that affect the amount of heat supplied to or taken away from a body include its mass, temperature change, and thermal properties. Heat capacity is the amount of heat required to raise the temperature of 1kg of a substance by 1 degree Kelvin. When a change of state occurs, such as melting, boiling, or freezing, latent heat is required without a change in temperature. Specific heat capacity and specific latent heat values are provided for various common substances.
This document discusses the electromagnetic spectrum. It begins with lessons on dispersion and the EM spectrum. It then defines electromagnetic waves and groups them by their properties and uses within the spectrum. The spectrum order from high to low frequency is given as gamma rays, X-rays, ultraviolet, visible light, infrared, microwaves, and radio waves. The document provides examples of uses and dangers of different types of electromagnetic radiation, including radiation used in medical imaging, cooking, night vision, remote controls, and more.
This document discusses the states of matter and kinetic molecular theory. It describes the five states of matter - solids, liquids, gases, plasmas, and Bose-Einstein condensates. For each state, it explains the physical properties including volume, shape, compressibility, and particle motion. It also covers phase changes between different states of matter caused by adding or removing heat energy, such as melting, freezing, boiling, and condensation. Additionally, it introduces concepts from kinetic molecular theory including the particle nature of matter, constant motion of particles, and perfectly elastic collisions between particles.
A 3D printing pen has been invented that allows solid structures to be drawn in thin air. The pen extrudes heated plastic thread that instantly cools and solidifies as it exits the tip, enabling the creation of 3D objects without software or technical knowledge. It weighs 7 ounces and plugs into an electrical outlet.
The document discusses whether the universe is infinite or finite. It introduces the Copernican principle, which states that Earth is not at the center of the universe, and the cosmological principle, which says that the universe looks the same in all directions and locations. The document also mentions how the solar system was originally thought to look, includes a distance-time graph demonstrating the expansion of the universe, and notes that the expansion occurs in all directions.
Is the universe infinite or does it simply [autosaved]Physics Amal Sweis
The document discusses whether the universe is infinite or finite. It introduces the Copernican principle, which states that Earth is not at the center of the universe, and the cosmological principle, which says that the universe looks the same in all directions and locations. The document also mentions how the solar system was originally thought to look, includes a distance-time graph demonstrating the expansion of the universe, and notes that the expansion occurs in all directions.
A 3D printing pen called the 3Doodler allows users to draw and extrude plastic thread in thin air or on surfaces to create 3D structures, requiring no software. The pen is powered and plug
This document discusses concepts related to kinetic energy, work, potential energy, and machines. It defines kinetic energy as the energy of motion, and states that an object's kinetic energy depends on its mass and speed. Kinetic energy is calculated using the formula KE=1/2mv^2. Work is done when an object's kinetic energy changes, and work depends on the applied force and distance moved. Potential energy is stored energy due to an object's position or arrangement, such as gravitational potential energy calculated as mgh. Mechanical advantage measures how machines multiply force, while efficiency indicates the percentage of energy input that does useful work.
This document discusses levers, moments, and balanced forces. It provides examples of levers in bones and joints. It defines an unbalanced system as one where anticlockwise moments do not equal clockwise moments, such as an uneven seesaw. Formulas are given for calculating moments as force x distance. The principle of moments states that a balanced seesaw has total clockwise moment equal to total anticlockwise moment. Sample calculations demonstrate using the principle of moments to determine balancing points on a seesaw and the maximum load a crane can lift.
The document discusses the benefits of exercise for mental health. Regular physical activity can help reduce anxiety and depression and improve mood and cognitive functioning. Exercise causes chemical changes in the brain that may help boost feelings of calmness, happiness and focus.
A force is any interaction that causes a change in the motion of an object. There are several key laws of motion:
1) Newton's First Law states that an object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
2) Newton's Second Law states that the acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object.
3) Newton's Third Law states that for every action, there is an equal and opposite reaction.
The document goes
This document covers key concepts in physics including:
- The difference between speed and velocity, with speed being a scalar quantity and velocity having both magnitude and direction
- Mass is a scalar quantity, while weight is a vector that points toward the center of the Earth
- Examples of scalar and vector quantities in physics including distance, speed, mass, and force
- Common units used to measure physical quantities like meters for distance and seconds for time
- Prefixes used in the International System of Units (SI) like milli, centi, and kilo
- An example problem calculating the speed of a car that traveled 10,000 meters in 6 minutes
This document contains information about various physics concepts including:
- The difference between speed and velocity, with speed being a scalar quantity and velocity having both magnitude and direction
- The difference between mass and weight, with mass being a scalar quantity and weight being a vector pointing toward the center of the Earth
- Examples of scalar and vector quantities in physics
- Common units used to measure physical quantities like distance, time, velocity, mass, and force
- Prefixes used with SI units like nano, micro, and kilo
- An example problem calculating the speed of a car that traveled a distance in a period of time
This document provides an overview of key concepts in kinematics, including:
- Speed is a scalar quantity that measures how fast something is moving, while velocity is a vector that includes both speed and direction.
- Mass is a scalar that measures the amount of matter in an object, while weight is a vector pointing toward the center of the Earth that represents the force of gravity on an object.
- Common physics quantities can be classified as either scalars or vectors, and standard units are provided for measuring displacement, time, velocity, mass, force, and other quantities.
This document provides an overview of key concepts in kinematics, including:
- Speed is a scalar quantity that measures how fast an object is moving, while velocity is a vector quantity that includes both speed and direction.
- Mass is a scalar that measures the amount of matter in an object, while weight is a vector that represents the force of gravity on the object.
- Common physics quantities include scalars like distance, speed, mass, and time as well as vectors like displacement, velocity, acceleration, and force.
- Standard units of measurement include meters for distance, seconds for time, meters/seconds for velocity and speed, kilograms for mass, and newtons for force.
Physics is the study of the natural world and how physical objects behave. It began in ancient Greece when early scientists called "physikoi" tried to understand the natural world using observations and experiments. Today, physics involves measuring various quantities accurately using standardized metric units like meters, kilograms, and seconds. Measurements in physics consist of a number and a unit, and the International System of Units (SI) precisely defines the fundamental base units and derived units used in physics.
This document provides instructions for measuring volume, temperature, and mass using common laboratory equipment. It describes how to properly read the meniscus of a graduated cylinder at eye level to determine volume within one uncertain digit. For temperature measurements, a thermometer should be read at eye level with the bulb not touching any surfaces. Mass is determined on a balance by positioning riders along the beams until the pointer is at zero, with the last digit placed being uncertain. Correct technique helps avoid parallax errors and provides accurate scientific measurements.
This document discusses heat transfer and the three main methods: conduction, convection, and radiation. Conduction involves the direct contact transfer of heat between objects. Convection involves the transfer of heat by the movement of molecules within a substance from warmer to cooler areas. Radiation involves the transfer of heat through space, such as the sun's rays causing sunburn.
This document discusses heat transfer and the three main methods: conduction, convection, and radiation. Conduction involves the direct contact transfer of heat between objects. Convection refers to the transfer of heat by the movement of molecules within a substance from warmer to cooler areas. Radiation involves the transfer of heat through space, such as the sun's rays causing sunburn. The document provides examples and descriptions of each type of heat transfer.
This document discusses the five states of matter: solid, liquid, gas, plasma, and Bose-Einstein condensate. It provides details on the properties and characteristics of each state, including that solids have a definite shape and volume, liquids have a definite volume but not shape, and gases are easily compressed and have no definite shape or volume. Additional topics covered include kinetic theory, fluids, phase changes, how heat and pressure affect boiling points and freezing points, and Boyle's law regarding the inverse relationship between gas pressure and volume.
This document discusses the five states of matter: solid, liquid, gas, plasma, and Bose-Einstein condensate. It provides details on the properties and characteristics of each state, including that solids have a definite shape and volume, liquids have a definite volume but not shape, and gases are easily compressed and have no definite shape or volume. Additional topics covered include kinetic theory, fluids, phase changes, how heat and pressure affect boiling points and freezing points, and Boyle's law regarding the inverse relationship between gas pressure and volume.
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2. Why is it colder in the
night than in the day?
The sun is the
greatest heat
source.
As the sun
comes up, it
warms earth.
As the sun goes
down, the heat is
taken away and
it cools off.
2
3. What will happen to this cold
snowman throughout the day
as the sun warms it up?
3
4. What would happen to the
temperature of the boiling water
in this kettle if I added ice cubes?
4
5. How is the change in
temperature of the snowman and
the boiling water related?
The temperature of
both the snowman
and the boiling
water changed to a
temperature that
was not really cold
or really hot, but
rather somewhere
in between.
5
6. “Temperature”
How hot or cold an object is.
Measured in degrees Celsius.
Temperature and heat are
NOT THE SAME.
It’s a measure of the average
kinetic energy of an individual
molecule.
6
7. Heat
The amount of thermal energy an
object has. It’s measured in joules or J.
A cup of hot tea has
heat energy , it is due
to the kinetic energy
(internal energy) of its
particles.
7
8. The small beaker of water
boils first
The large beaker
contains more water
molecules so it
needs more thermal
energy (heat) to
reach the same
temperature (100°C)
as the small one.
8
9. A swimming pool at 30°C is
at a lower temperature than
a cup of tea at 100°C.
BUT
the swimming pool
contains more water,
so it stores more
thermal energy or
heat.
9
10. Thermometers
A thermometer (in Greek: thermos
means "hot" and metron “meansure")
It’s a device that measures temperature
using a physical Principle.
The Galilean thermometer:
The first thermometer (1953) was
really a thermoscope. It is not called
a thermometer, because the scale was
arbitrary. The egg-sized globe at the
top is the sensor. The gas within it
expands or contracts, and the liquid
level rises and falls.
http://www.youtube.com/watch?v=W_xc-6662f8 10
11. Types of Thermometer
1- Contact thermometers:
(1) Liquid-in-glass thermometers.
(2) Electric thermometers:
a) Thermistors.
b) Thermocouples.
(3) Liquid crystal thermometers.
*2- Non-contact thermometers:
Infrared (IR) thermometers.
11
12. 1. Liquid-in-glass thermometer
Liquid thermometers have been around
for almost 300 years.
These rely on the expansion of a liquid
(Mercury or Alcohol) with temperature.
12
13. Liquid-in-glass thermometer
The liquid is contained in a sealed
glass bulb and it expands into the
fine bore in the thermometer stem.
Temperature is read using a scale etched
along the stem.
The relationship between the temperature
and the column's height is linear over the
small temperature range for which the
thermometer is used.
13
17. Thermistors, invented by Samuel Ruben
1930, are very temperature sensitive.
Their resistance decreases
as the temperature
increases, so the
Electric current
increases,
(and vice versa).
2. Electrical thermometers
a) Thermistors = THERMal resISTORS
17
19. Thermistors
Example Applications:
1. Temperature measurement.
2. Time delay (self heating from large current ‘opens’ the
thermistor so it can be used as a slow switch). Heating = I2 R,
where R is the resistance and I is the current.
3. Surge suppression when a circuit is first energized. Current
needs to flow through the thermistor for awhile to heat it so
that it ‘opens’, and acts again as a switch.
19
20. Thermistors can be classified into two types
depending on the sign of k.
a) If k is negative, the resistance decreases with
increasing temperature, and the device is called a
negative temperature coefficient (NTC)
thermistor.
b) If k is positive, the resistance increases with
increasing temperature, and the device is called a
positive temperature coefficient (PTC) thermistor,
Posistor.
20
22. b) Thermocouples
A thermocouple is a pair of junctions formed
from two dissimilar metals. One at a reference
temperature (e.g. 20⁰C) and the other junction
at the temperature to be measured.
A temperature
difference will
produce an
electric voltage
that depends
on this temp.
difference.
22
23. Why use thermocouples to
measure temperature?
◦ They are inexpensive.
◦ They are rugged and reliable.
◦ They can be used over a wide
temperature range.
23
24. 3. Liquid crystal thermometers
A liquid crystal thermometer (or plastic strip
thermometer) is a type of thermometer that contains
heat-sensitive liquid crystals in a plastic strip that
change color to indicate different temperatures.
In medical applications, liquid crystal
thermometers may be used to read body
temperature by placing against the forehead, usually
called “forehead thermometers”.
When it’s cold
When it’s used to
measure temp.
24
25. Temperature scales
Celsius Scale:
Celsius is the metric scale for
measuring temperature.
Water freezes at 0ºC and boils at
100ºC.
Fahrenheit Scale: water freezes
at 32 °F, and boils at 212 °F
[F = 1.8C + 32]
25
26. Kelvin scale
In the Kelvin scale temperature is
measured in Kelvin units (K)
Formula (273+ºC)= Kelvin
Absolute zero (0 K) :
The temperature in which all
molecular motion stops
26
27. Units for measuring heat
Like any type of energy, the SI unit for heat is the
Joule.
Calorie: the name calorie is used for two units of
energy:
a) The small calorie or gram calorie (symbol: cal) is
the amount of energy needed to raise the temperature
of one gram of water 1⁰C.
b) the large Calorie, or ”Kg calorie”, “nutritionist's
calorie”, (symbol: Cal) is the amount of energy needed
to raise the temperature of 1 Kg of water by 1⁰C.
The large calorie is thus equal to 1000 small calories
or one kilocalorie (Cal = 1000 cal =1 Kcal ).
1 Cal is about 4.2 kilojoules (4.186 KJ), and
1 cal = 4.2 J
27
28. Thermal Equilibrium
Two bodies are said to be at thermal equilibrium if they are at the
same temperature. This means there is no net exchange of thermal
energy between the two bodies. The top pair of objects are in
contact, but since they are at different temps, they are not in
thermal equilibrium, and energy is flowing from the hot side to the
cold side.
hot coldheat
26°C 26°C
No net heat flow
The two purple objects are at the same temp and, therefore are in
thermal equilibrium. There is no net flow of heat energy here.
29. Specific Heat Capacity
S.H.C. is defined as the amount of thermal energy needed to
raise a unit mass of substance a unit of temperature. Its symbol
is C (or s.h.c.).
For example, the specific heat of water is : C = 1 cal /(g·ºC),
or 4.186 J/(g·ºC), or 4186 J/Kg ºC ≈ 4200 J/Kg ºC)
Water has a very high specific heat, so it takes more energy to
heat up water than it would to heat up most other substances, of
the same mass, by the same amount of temp. Oceans and lakes
act like “heat sinks” storing thermal energy absorbed in the
summer and slowly releasing it during the winter. Large bodies
of water thereby help to make local climates less extreme in
temperature from season to season.
29
30. Specific Heat Equation
Q = m C T
Q = thermal energy (J, or KJ, or cal, or Cal …)
m = mass (g, or Kg …)
T = change in temp. (ºC, or ºF, or Kelvin)
C = specific heat capacity
Example1: The specific heat of silicon is 703 J / (kg · ºC).
How much energy is needed to raise the temperature
of a 7 kg chunk of silicon by 10ºC ?
Solution:
703 J
kg · ºCQ = 7 kg * [ ]*10 ºC = 49 210 J
☺ Visual experiments: Measure Specific Heat Capacity of Ethanol:
http://www.chm.davidson.edu/vce/calorimetry/SpecificHeatCapacityofEthanol.html
30
31. Example2:
How much energy does it take to raise the temperature
of 50 g of copper by 10 ºC?
Example 3:
If we add 30 J of heat to 10 g of aluminum, by how
much will its temperature increase?
Example 4:
216 J of energy is required to raise the temperature of
aluminum from 15o to 35oC. Calculate the mass of
aluminum.(S.H.C. of aluminum is 0.90 JoC-1g-1).
Example 5:
The initial temperature of 150g of ethanol was 22oC.
What will be the final temperature of the ethanol if 3240 J
was needed to raise the temperature of the ethanol?
(Specific heat capacity of ethanol is 2.44 JoC-1g-1).
Answers: 192.5 J, 3 ºC, 12 g, 30.9 ºC. 31
32. Some Materials’ Specific Heat Capacity (J/g ºC)
Water 4.18 6 Air 1.01
Ice 2.03 Glass 0.84
Al 0.385C Aluminum 0.902
Graphite 0.720 NaCl 0.864
Mercury 0.14 Granite 0.79
Fe 0.451 Concrete 0.88
Cu 0.385 Wood 1.76
Au 0.128
C2H5OH (ethanol) 2.46
(CH2OH)2 (antifreeze) 2.42
32
33. H.C. of an object is the energy required to change
the temperature of this object by 1 degree.
Equation: or
Thermal capacity Q, Thermal capacity 1/ T
The SI unit for heat capacity is J/K
It can also be expressed in KJ/K, J/ºC, Cal/ºC …
E.g. Night storage heaters (page 106 in your Course book).
Exercise: Solve the previous examples (1-5) to calculate the
thermal capacity for each object.
Answers: 4921 J/ºC, 19.25 J/ºC, 10 J/ ºC, 10.8 ºC, 364 J/ ºC .
Homework: make a comparison table for the thermal (heat) capacity
and the s.h.c. (C).
Heat capacity = Q / T Heat capacity = m * C
☺ Visual experiment: T vs. Q to calculate heat capacity:
http://www.chm.davidson.edu/vce/calorimetry/heatcapacity.html
33
34. Latent Heat
The word “latent” comes from a Latin word that means
“Hidden.” When a substance changes phases (liquid solid
or gas liquid) energy is transferred without a change in
temperature. For example, to turn water ice into liquid water,
energy must be added to bring the water to its melting point,
0ºC. This is not enough, additional energy is required to
change 0 ºC ice into 0 ºC water. The energy supplied to water
increases its internal energy but does not raise its temp., it
breaks down the bonds between, the particles. This energy is
called latent heat of fusion.
34
35. Latent Heat (L)
Latent heat of fusion: the energy needed to
convert a solid into a liquid at the melting
temperature.
Specific Latent heat of fusion: the energy needed
to convert 1Kg of a solid into liquid at the melting
temperature.
Latent heat of vaporization: the energy needed to
change a liquid into vapor (gas) at the boiling
temperature.
Specific Latent heat of vaporization: the energy
needed to change 1Kg of a liquid into vapor (gas)
at the boiling temperature.
35
36. Latent Heat Formula
S.L.H. = energy supplied / mass
i.e. Lf = Q/m & Lv = Q/m, or Q = m Lf & Q = m Lv
Q = thermal energy Units examples: J, KJ, Cal., Kcal.
m = mass Kg, g
Lf = Specific Latent heat of fusion J/Kg, KJ/Kg, J/g, Cal/Kg
Lv = Specific Latent heat of vaporization J/Kg, KJ/Kg, Cal./Kg
Example: Gold melts at 1063 ºC, what is the amount of heat
needed to melt 5 grams of solid gold at this temp. given that Lf
(the specific latent heat of fusion) for gold is 6440 J / kg. ?
Answer: Q = 32 J.
Homework: make a comparison table for the thermal (heat)
capacity, the s.h.c. (C), the latent heat & the specific latent heat.
36
37. Specific Latent Heat & Specific Heat
Substance Specific Heat (in J/kg·ºC)
Ice 2090
Liquid water 4186
Steam 1970
Example: Superman can vaporize a 1800 kg ice-monster
with his heat ray vision. The ice-monster was at -20 ºC.
After being vaporized the steam was heated to 135 ºC.
How much energy did Superman expend?
For Water: Lf = 3.33 ×105 J/kg; Lv = 2.26 × 106 J/kg
Information you will need:
ICE
-20 ºC
ICE
0 ºC
WATER
0 ºC
VAPOR
100 ºC
WATER
100 ºC
VAPOR
135 ºC
Heating Melting Heating Boiling Heating
S.H.C. Lf S.H.C. Lv S.H.C.
37
38. Solution steps
1. The energy needed for heating ice from -20ºC to the melting point:
Q1 = m*C*T = (1800 kg) (2090 J/kg·ºC) (20 ºC) = 75240000 J
2. The energy needed for turning ice into water at 0ºC:
Q2 = m*Lf = (1800 kg) (3.33 × 105 J / kg) = 5994 × 105 J
3. The energy needed for heating water from 0ºC to the boiling point:
Q3 = m*C*T = (1800 kg) (4186 J/kg·ºC) (100ºC) = 753480000 J
4. The energy needed for turning water into steam at 100 ºC:
Q4 = m*Lv = (1800 kg) (2.26 × 106 J/kg) = 4068 × 106 J
5. The energy needed for heating steam to 135 ºC:
Q5= m*C*T = (1800 kg) (1970 J/kg·ºC) (135 ºC) = 478710000 J
Total energy expended by Superman = 75240000 + 5994 × 105 +
753480000 + 4068 × 106 + 478710000 = (75.24 × 106) + (599.4 × 106) +
(753.48 × 106) + (4068 × 106) + (478.71 × 106) = 5974.83 × 106 J
38
39. Thermal Expansion
As a material heats up its particles move or vibrate more
vigorously, and the average separation between them increases.
This results in small increases in lengths and volumes.
Buildings, railroad tracks, bridges, and highways contain
thermal expansion joints to prevent cracking and warping due
to expansion.
Factors which affect the expansion of solids:
Original length & temperature raise (direct), material type.
39
40. What do you see in these pictures?
What is meant be expansion?
It is the difference between the original size of an object and its size
when its heated (or cooled).
40
41. Some real-life problems due to expansion
On a hot day concrete runway sections in airport
expands and this cause cracking. To solve this
problem we leave small gabs between sections.
On a hot day concrete bridges expand. To solve this
problem, we leave small gab at one end and support the
other end with rollers.
Telephone wire contract on cold days. To solve this
problem, we leave wires slack so that they are free
to change length.
On a hot day railway lines expand. To solve this
problem, gaps are left between sections of railway
lines to avoid damage of the rails as the expand in
hot weather.
41
42. Bimetallic Strip
A bimetallic strip is a strip of two different metals — often steel on
one side and brass on the other. When heated the strip curves
because the metals have different coefficients of thermal expansion.
Brass’s coefficient is higher, so for a given temperature change, it
expands more than steel. This causes the strip to bend toward the
steel side. The bending would be reversed if the strip were made
very cold.
cold strip
hot strip
handle steel (brass on
other side)
Top view
steel side
brass side
Side view
42
43. Thermostats
Bimetallic strips are used in thermostats, at least in some
older ones. When the temperature changes, the strip bends,
making or breaking an electrical circuit, which causes the
furnace to turn on or shut off.
Some applications to thermostat in industry :
electric irons, home heating/cooling systems, ovens,
refrigerators, fire alarms, fish tanks, car thermostat
.
43
44. Expansion of liquids
What do you see in the picture below?
Explain what happen when liquids are heated?
When a liquid is heated, its molecules gain kinetic
energy and vibrate more vigorously. As the vibration
become larger, the molecules are pushed further
apart and the liquid expands slightly in all directions.
44
45. List the factors which affect the
expansion of liquids?
temperature & liquid volume (direct), liquid type.
*The effect of temperature on volume and
density of water:
45
46. Expansion of gases
Compare the expansion of gases to that of solids and liquids?
The expansion of gases is much more larger than that of solids or
liquids under the same rise in temperature.
The effect of temperature on gas volume under constant
pressure
The volume of a gas is directly proportional to the Kelvin
temperature under constant pressure (Charlie's Law).
When the temperature of a gas is increased, the molecules move
faster and the collisions become more violent thus they spread away
from each other causing the volume to increase.
inside and outside
pressures
are balanced. 46