Physical changes are characterized by the following:
Definition of chemical change.
Chemical Changes are characterized by the following:
Chemistry • A physical science that involves the study of the properties, composition,& structure of matter and the changes it undergoes.
What is a chemical? • Any substance that has a definite composition or is used or produced in a chemical process. • Sugar is an example of a chemical
• Everything that has mass and volume is called matter • Can be simple as in elements on the Periodic Table • or complex molecules as atoms combineElements in the same verticalrow will behave similar inchemical reactions
Three Major Classes of Elements• Metals- located on the left of the Periodic Table- most of the elements• Non-Metals- located on the right of the Periodic Table• Metalloids- on the zigzag line between Metals and Nonmetals- have properties that are skewed- ie… Silicon is conductive• You will have to memorize the symbol and element name for approximately 40 common elements
Properties of Metals Metals are goodconductors of heat andelectricity Metals are malleable (can beshaped) Metals are ductile (canbe drawn into wires) Metals have high tensilestrength Metals have luster
Properties of NonmetalsCarbon, the graphite in “pencil lead” is a greatexample of a nonmetallic element. Nonmetals are poor conductors of heat andElectricity Nonmetals tend to be brittle Many nonmetals are gases at roomtemperature
Atoms Unite To Form Compounds• Chemical Formula C16H10 N2O2. indicates number and type of atoms within the molecule The formula to the left is the molecule What type of atoms and how for indigo: many are there in one molecule?
What is not matter? • Light • Electricity • Sound
• Fixed composition• Cannot be separated into simpler substances by physical methods (physical changes)• Can only be changed in identity and properties by chemical methods• Properties do not vary- Unique Density, Constant Boiling and Melting Points
Elements Compounds• Cannot be • Chemically joined decomposed into elements- Can be simpler decomposed into simpler substances by substances by chemical changes, chemical changes always in a definite ratio
• Variable composition• Components retain their characteristic properties• May be separated into pure substances by physical methods sifting, evaporation, magnetism, etc…• Mixtures of different compositions may have widely different properties• Do NOT have definite boiling/melting points
Homogenous mixtures look the samethroughout but can be separated byphysical meansExamples: salt water, soda
• Have the same composition throughout• Components are indistinguishable• Can exist between all phases of matter: air (gases) brass (alloy- blend of multiple metals -solids) soda (gas, solid, liquid)
Adding Liquids Together • Miscible- will mix- water and alcohol • Immiscible- wont mix water and oil
Solutions are homogenous mixtures thatdo not scatter light. These mixtures arecreated when something is completelydissolved in pure water. Therefore, theyare easily separated by distillation orevaporation. Appear in one phase ofmatterExamples: sugar water, salt water
Parts of a solution • Solvent- part that does the dissolving- water is our universal solvent • Solute- part that was dissolved (salt)
How do we increase solubility of a solid into a liquid• Heat it- more collisions between solute and solvent• Mix- Fresh solvent to solute• Crush- more surface area- more contact
Increase solubility of a gas in a liquid • Henrys Law- solubility of the gasis directly proportional to the pressure above the liquid- • Effervescence- rapid escape of gas from liquid • Decrease temperature- slows down diffusion
Heterogeneous mixtures are composed oflarge pieces that are easily separated byphysical means (ie. density, polarity,metallic properties, size).Pond Water, Vegetable Soup- SuspensionsVisible particlesStarch Water: invisible to the eye :colloid
Colloids are Tricky • Some heterogeneous mixtures appear as solutions to the eye: • Blood, Milk, starch water • Need a test: Tyndall Effect a light will scatter the suspended particles
MATTER yes Can it be physically no separated? MIXTURE PURE SUBSTANCEyes Is the composition no yes Can it be chemically no uniform? decomposed? Homogeneous Heterogeneous Mixture Mixture Compound Element (solution) Colloids Suspensions Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Physical Properties – Observable traits of a material that may be measured without altering the substanceExamples: Mass, Color, Melting Point, Boiling Point, Density
We can use physical properties to separate mixtures: Please determine a method to separate the following and determine the type of matter:Oil and WaterIron and SandSand and SaltSulfur and Sugar
What are thephysical propertiesof the substance to the right?What do you think the material is that made thisbracelet?How could you be sure? Density- the amount of material in a given volume- unique to the material
Chemical Change-an irreversible change that changes theidentity and make up of the material Examples: Rusting Burning
• There is no observable change in the quantity of matter during a chemical reaction or a physical change.In other words, matter cannot be created nor destroyed. It is just converted from one form to another
Energy comes in two forms :Kinetic Energy: MovementPotential Energy: Stored
All matter, regardless of state, undergoes physical and chemical changes. These changes can be microscopic or macroscopic.
A physical change occurs when thesubstance changes state but does not changeits chemical composition. It is notpermanent and is reversible! ExamplePhase Changes!
Physical Change For example: Ice melting to water. The form or appearance has changed, but the properties of that substance are the same (i.e. it has the same melting point, boiling point, chemical composition, etc.)
• Melting point • Density• Boiling point • Electrical conductivity• Vapor pressure • Solubility• Color • Adsorption to a• State of matter surface• Specific Heat • Hardness
Names of Water Phase ChangesEndothermic Requires Exothermic Gives Energy to go forward energy off • Melting: Solid Liq • Condensation • Boiling (forced) Gas Liq Liquid Gas • Freezing: • Evaporation ( spon) Liq Solid Liquid Gas • Deposition: • Sublimation Gas Solid Solid Gas
A substancechanges intosomething new.It is irreversible.
Indications of A Chemical Reaction • Bubbles- gas given off • Change in energy- becomes warm- exothermic becomes cool- endothermic light is given off • A precipitate (solid) forms • Sometimes a change in color-
All Chemical Changes can be written as a reaction • A + B AB • A, B are the starting materials- reactants • AB is the result- product
• Reaction with acids • Ability to act as• Reaction with bases reducing agent (alkalis) • Reaction with other• Reaction with oxygen elements (combustion) • Decomposition into• Ability to act as simpler substances oxidizing agent • Corrosion
• Physical and chemical properties may be intensive or extensive.
• Intensive properties such as density, color, and boiling point do not depend on the size of the sample of matter and can be used to identify substances.•
• Extensive properties such as mass and volume do depend on the quantity of the sample.
• Physical properties are those that we can determine without changing the identity of the substance we are studying.
• The physical properties of sodium metal can be observed or measured. It is a soft, lustrous, silver-colored metal with a relatively low melting point and low density.• Hardness, color, melting point and density are all physical properties.
Specific Heat• Physical Property that is unique to the material• Amount of energy required to heat 1 gram of a substance by 1 degree Celsius• -Why do you choose to sit on the wooden bleachers on a cold fall day for a football game instead of the metal bleachers?
• Chemical properties describe the way a substance can change or react to form other substances.• These properties, then, must be determined using a process that changes the identity of the substance of interest.
• One of the chemical properties of alkali metals such as sodium and potassium is that they react with water. To determine this, we would have to combine an alkali metal with water and observe what happens.• In other words, we have to define chemical properties of a substance by the chemical changes it undergoes.
& The Kinetic Molecular Theory•All matter is made of atom and molecules that act as tiny particles•These particles are always in motion (yes even in solids)•The higher the temperature the faster the particles move-•Kinetic energy is directly proportional to KelvinTemperature ( bigger particles move slower)
•Have a definite shape •Have a definite volume Kinetic Molecular TheoryMolecules are held close togetherand there is very little movementbetween them. Vibrational
•Have an indefinite shape •Have a definite volumeKinetic Molecular Theory:Atoms and molecules have morespace between them than a soliddoes, but less than a gas (ie. It ismore “fluid”.) Has 2 dimensionalmotion- can slide past each other
•Have an indefinite shape •Have an indefinite volumeKinetic Molecular Theory:Molecules are moving in randompatterns with varying amounts ofdistance between the particles.
At 100°C, water becomes water Between 0°C and 100 vapor, a gas. °C, water is a liquid. Molecules can In the liquid state, move randomly water molecules are over large close together, but distances. can move about freely.Below 0°C, watersolidifies to becomeice. In the solid state,water molecules areheld together in arigid structure.
Changing states requires energy in either the form of heat. Changing states may also be due to the change in pressure in a system.Heat of formation, Hf. Heat of vaporization, Hv
Plasma is by far the most common formof matter in the universe (not here onEarth). Plasma in the stars and in thetenuous space between them makes upover 99% of the visible universe andperhaps most of that which is notvisible. Fluorescent Light Bulbs…
Star formation in the Eagle NebulaSpace Telescope Science Institute , NASA(below) (Above) X-ray view of Sun from Yohkoh, ISAS and NASA
Plasma radiation within the PrincetonTokamak during operation.
Laser plasma interaction during inertialconfinement fusion test at theUniversity of Rochester.
Plasma consists of a collection of free-moving electrons and ions - atoms thathave lost electrons. Energy is needed tostrip electrons from atoms to make plasma.The energy can be of various origins:thermal, electrical, or light (ultravioletlight or intense visible light from a laser).With insufficient sustaining power,plasmas recombine into neutral gas.
EXAMPLES: •Printing on plastic food•Computer chips and containersintegrated circuits •Energy-efficient window•Computer hard drives coatings•Electronics •High-efficiency window•Machine tools coatings•Medical implants and •Safe drinking waterprosthetics •Voice and data•Audio and video tapes communications components•Aircraft and automobile •Anti-scratch and anti-glareengine parts coatings on eyeglasses and other optics