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Gases & the Atmosphere
 

Gases & the Atmosphere

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  • Imagine trying to fit a room full of people into a closet. If the people continue to try and move around they will be bumping into the walls more frequently.
  • Imagine trying to fit a room full of people into a closet. If the people continue to try and move around they will be bumping into the walls more frequently.
  • Imagine trying to fit a room full of people into a closet. If the people continue to try and move around they will be bumping into the walls more frequently.
  • Imagine trying to fit a room full of people into a closet. If the people continue to try and move around they will be bumping into the walls more frequently.
  • Imagine trying to fit a room full of people into a closet. If the people continue to try and move around they will be bumping into the walls more frequently.
  • Imagine trying to fit a room full of people into a closet. If the people continue to try and move around they will be bumping into the walls more frequently.
  • Imagine trying to fit a room full of people into a closet. If the people continue to try and move around they will be bumping into the walls more frequently.
  • Imagine trying to fit a room full of people into a closet. If the people continue to try and move around they will be bumping into the walls more frequently.
  • Imagine trying to fit a room full of people into a closet. If the people continue to try and move around they will be bumping into the walls more frequently.
  • Imagine trying to fit a room full of people into a closet. If the people continue to try and move around they will be bumping into the walls more frequently.
  • Imagine trying to fit a room full of people into a closet. If the people continue to try and move around they will be bumping into the walls more frequently.
  • Imagine trying to fit a room full of people into a closet. If the people continue to try and move around they will be bumping into the walls more frequently.
  • Imagine trying to fit a room full of people into a closet. If the people continue to try and move around they will be bumping into the walls more frequently.
  • Imagine trying to fit a room full of people into a closet. If the people continue to try and move around they will be bumping into the walls more frequently.
  • Imagine trying to fit a room full of people into a closet. If the people continue to try and move around they will be bumping into the walls more frequently.
  • Imagine trying to fit a room full of people into a closet. If the people continue to try and move around they will be bumping into the walls more frequently.

Gases & the Atmosphere Gases & the Atmosphere Presentation Transcript

  • Gases & The Atmosphere CHEMISTRY 30S UNIT 2
  • Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Our atmosphere is made of several gases. The composition has changed over time and continues to change.
  • Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Present Composition of Our Atmosphere Earth’s air is composed of two types of gases: permanent and variable. The gases are called permanent because their amounts have not significantly changed in recent history. The permanent gases in the atmosphere by percentage are: Nitrogen 78.1% Oxygen 20.9% These two gases comprise 99% of the Earth’s lower atmosphere.
  • Gases & The Atmosphere CHEMISTRY 30S UNIT 2
    • Some of the other permanent gases are:
    • Argon 0.9% Neon 0.002% Helium 0.0005% Krypton 0.0001% Hydrogen 0.00005%
    • As their name suggests, variable gases
      • Water vapor 0 to 4% Carbon Dioxide 0.035% Methane 0.0002% Ozone 0.000004%
  • Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Historical Development of the Measurement of Pressure Galileo (1564 – 1642) Otto von Guericke (1643-1645) Christiann Huygens (1661) Joseph Louis Gay-Lussac (1808) Evangelist Torricelli (1643) Blasie Pascal (1648) John Dalton (1801) Amadeo Avogadro (1811)
  • Gases & The Atmosphere CHEMISTRY 30S UNIT 2
    • Galileo (1564 – 1642)
      • Galileo developed the suction pump. He used air to draw underground water up a column, similar to how a syringe draws water. He was perplexed as to why there was a limit to what height the water could be raised.
  • Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Evangelista Torricelli (1643) Evangelista Torricelli developed the first barometer. He carried on Galileo’s work by determining the limit to the height with which Galileo’s pump could draw water was due to atmospheric pressure. He invented a closed- end tube filled with mercury into a pan of mercury at sea level. The height of the column of mercury in the tube (in mmHg) is equal to the atmospheric pressure acting on the mercury in the pan.
  • Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Otto von Guericke (1643-1645) Otto von Guericke made a pump that could create a vacuum so strong that a team of sixteen horses could not pull two metal hemispheres apart. Otto von Guericke reasoned that the hemispheres were held together by the mechanical force of the atmospheric pressure rather than the vacuum.
  • Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Blaise Pascall (1648) Blaise Pascal used Torricelli’s “barometer” and traveled up and down a mountain in southern France. He discovered that the pressure of the atmosphere increased as he moved down the mountain. Sometime later the SI unit of pressure, the ‘Pascal’, was named after him.
  • Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Christian Huygens (1661) Christiaan Huygens developed the manometer to study the elastic forces in gases.
  • Gases & The Atmosphere CHEMISTRY 30S UNIT 2 John Dalton (1801) John Dalton stated that in a mixture of gases the total pressure is equal to the sum of the pressure of each gas, as if it were in a container alone. The pressure exerted by each gas is called its partial pressure.
  • Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Joseph Louis Guy-Lussac (1808) Joseph Louis Gay-Lussac observed the law of combining volumes. He noticed that, for example, two volumes of hydrogen combined with one volume of oxygen to form two volumes of water.
  • Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Amadeo Avagadro (1811) Amadeo Avogadro suggested, from Gay- Lussac’s experiments conducted 3 years earlier, that the pressure in a container is directly proportional to the number of particles in that container (known as Avogadro’s Hypothesis). This can be illustrated by blowing up a balloon, ball or tire: the more air is added the larger the container becomes due to increased pressure.
    • Gas pressure is caused by the force of gaseous molecules colliding with the sides of its container.
    • The atmosphere, which is a mixture of gases about 100 km thick, exerts pressure as a result of its weight and the kinetic energy of the air particles.
    • This pressure is called atmospheric pressure, air pressure, or barometric pressure.
    Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Atmospheric Pressure
    • Pressure can be measured using several devices or instruments. Air pressure is measured with a barometer, whereas gas pressure is measured with a monometer.
    • A simplified barometer uses a dish filled with mercury and a tube of mercury inverted in the dish. The height of mercury supported in the tube is the air pressure in mmHg .
    • A manometer usually has a bulb or glass container on one end and can be open or closed on the other. A liquid, often mercury, is placed in a U-shaped tube. The pressure is measured by finding the difference in height on both sides of the tube.
    Gases & The Atmosphere CHEMISTRY 30S UNIT 2
  •  
    • Atmospheric pressure, air pressure, barometric pressure or gas pressure can be measured in 3 different units.
      • Atmosphere (atm)
      • Kilopascals (kPa)
      • Millimeters of mercury (mm Hg)
    • Standard Atmospheric Pressure is equal to:
      • 1 atm, 101.3 kPa, or 760 mmHg
    Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Units for Pressure
    • It may be necessary to convert one unit to another. The method best utilized is the Unit Factor Label Method.
    • Example:
      • Convert 720 mm Hg to atmospheres.
      • 720 mmHg x 1 atm/760 mmHg = .947 atm
    Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Units for Pressure
    • In the open-ended manometer, the pressure of the gas is related to the height difference, h, of the mercury (or other liquid) in both sides of the U-tube.
    • It is called open-ended because one end is exposed to the gas pressure and the other end is open to the atmosphere.
    Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Open Ended Manometer
    • When the pressure of the trapped gas (P gas ) is equal to the atmospheric pressure (P atm ) the height on both sides of the U-tube are equal.
    • When the pressure of the trapped gas is greater than the atmospheric pressure, the height of the liquid in the open side of the U-tube will be greater than the closed side.
    • The opposite is true if the atmospheric pressure is greater than the gas pressure.
    Gases & The Atmosphere CHEMISTRY 30S UNIT 2
  • Gases & The Atmosphere CHEMISTRY 30S UNIT 2
    • To calculate the pressure of the trapped gas when the gas pressure is greater than the atmospheric pressure
    • P gas = P atm + h
    • To calculate the pressure of the trapped gas when atmospheric pressure is greater than gas pressure
    • P gas = P atm - h
    Gases & The Atmosphere CHEMISTRY 30S UNIT 2
    • Example 1
    • Calculate the gas pressure in kilopascals (kPa) in the manometer shown below.
    Gases & The Atmosphere CHEMISTRY 30S UNIT 2
    • In the closed tube manometer, the pressure of the gas is related to the height difference, h, of the mercury (or other liquid) in both sides of the U-tube.
    • It is called closed-ended because one end is closed and the other end is open to the atmosphere or gas.
    Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Closed Tube Manometer
  • Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Measuring Gas Volume Worksheet
  • Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Boyle’s Law Online Activity
    • We can use the kinetic molecular theory to explain how Boyle's Law works. Decreasing the volume of a sample of gas, while keeping the temperature constant , would result in the same number of molecules squeezed into a smaller space. This will increase the number collisions of the gas molecules with the sides of the container. The increased frequency will result in a higher force, or pressure , on the walls of the closet than the walls of the room. An increased number of collisions means an increased pressure.
    Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Boyle's Law
    • Decreasing the volume of a sample of gas, while keeping the temperature constant , would result in the same number of molecules squeezed into a smaller space. This will increase the number collisions of the gas molecules means an increased pressure .
    Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Boyle's Law
    • According to the kinetic molecular theory, we should be able to compress a gas down to a volume of zero. A gas that behaves in this way is called an ideal gas . Ideal gases do not have any forces of attraction so they do not condense when they are compressed. The particles of ideal gases do not have any volume, so you would be able to compress them to a volume of zero. The concept of an ideal gas was used to simplify the relationship between pressure , volume and other factors. These behaviours general hold at low pressures and higher temperatures where condensation is not a factor. For the sake of this course, we will assume that all gases are ideal gases.
    Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Boyle's Law
    • The formula for the law is:
    • where:
      • V is the volume of the gas
      • p is the pressure of the gas
      • k is a constant value representative of the pressure and volume of the system.
    • Forcing the volume V of the fixed quantity of gas to increase, keeping the gas at the initially measured temperature, the pressure p must decrease proportionally. Conversely, reducing the volume of the gas increases the pressure.
    Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Boyle's Law
    • Boyle's law is commonly used to predict the result of introducing a change, in volume and pressure only, to the initial state of a fixed quantity of gas. The "before" and "after" volumes and pressures of the fixed amount of gas, where the "before" and "after" temperatures are the same (heating or cooling will be required to meet this condition), are related by the equation:
    Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Boyle's Law
  • Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Boyles Law & The Cartesian Diver
  • Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Charles’ Law Online Activity
    • Jacques Charles, a French scientist, only had a basic knowledge in mathematics and almost no science education. With the popularity of hot-air balloons in his time, investigated the expansion rates of different gases due to temperature changes. He used an apparatus very similar to that of Boyle. He took gases trapped in J-tubes and immersed them in water baths with varying temperatures. Regardless of the gas tested, he found that for every 1 degree Celsius change, the volume changed . When the temperature was increased by 273°C, the volume doubled.
    Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Charles Law
    • Charles' law is a gas law and specific instance of the ideal gas law, which states that:
      • At constant pressure, the volume of a given mass of an ideal gas increases or decreases by the same factor as its temperature (in kelvin) increases or decreases.
    Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Charles Law
    • The formula for the law is:
    • where:
      • V is the volume of the gas
      • T is the temperature of the gas (measured in Kelvins )
      • k is a constant.
    • The relationship between the volume of a gas at constant pressure is directly proportional to the temperature applied to the system.
    Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Charles Law
    • To maintain the constant, k , during heating of a gas at fixed pressure, the volume must increase. Conversely, cooling the gas decreases the volume. The exact value of the constant need not be known to make use of the law in comparison between two volumes of gas at equal pressure:
    Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Charles Law
  • Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Absolute Zero
    • Robert Boyle discovered that pressure and volume were inversely related. Jacques Charles discovered that temperature and volume were directly related. Joseph Gay-Lussac (1778-1850) carried on Charles’ work and discovered the relationship between temperature and gas pressure. Gay-Lussac determined that if the volume and the amount of a gas are held constant, increasing temperature of a gas will increases the pressure – a direct relationship. If we graph pressure and temperature data, we would find that it is a linear relationship.
    Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Gay Lussac's Law
  • Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Gay Lussac's Law
    • If we examine the temperature-pressure relationship of a gas using the kinetic molecular theory, an increase in the temperature of a gas increases the kinetic energy of the gas and thus the speed of the particles and the frequency of collisions with the sides of the container. We would then to expect that an increase in temperature should cause an increase in the pressure of a gas at constant volume because the increased frequency of collisions would increase the force applied to the sides of the container.
    Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Gay Lussac's Law
    • As with Boyle’s Law and Charles’ Law, we must first determine whether the change presented will increase or decrease the original value. Then we determine which ratio will produce this change. As with Charles’ Law, temperature must be in Kelvin .
    Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Gay Lussac's Law
    • The formula for the law is:
    • where:
      • P is the pressure of the gas
      • T is the temperature of the gas (measured in Kelvins )
      • k is a constant.
    • The pressure of a fixed amount of gas at fixed volume is directly proportional to its temperature in kelvins .
    Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Gay Lussac's Law
    • This law holds true because temperature is a measure of the average kinetic energy of a substance; as the kinetic energy of a gas increases, its particles collide with the container walls more rapidly, thereby exerting increased pressure.
    • Simply put, if you increase the temperature you increase the pressure.
    • For comparing the same substance under two different sets of conditions, the law can be written as:
    Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Gay Lussac's Law
  • Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Combined Gas Law It is not always easy to keep the temperature, pressure or volume constant when doing experiments. Therefore, a combined gas law equations was developed using the three laws: Boyle’s, Charles’, & Gay-Lussac’s.
  • Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Combined Gas Law Task: Using the three laws try and develop 1 equations, which uses pressure, temperature and volume.
  • Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Combined Gas Law Step 1: Write Boyles Law Step 2: Multiply by Charles Law Step 3: Multiply by Gay-Lussac’s Law Step 4: Take the Square root
  • Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Combined Gas Law P 1 V 1 = P 2 V 2 T 1 T 2
  • Gases & The Atmosphere CHEMISTRY 30S UNIT 2 Gas Laws
  • Gases & The Atmosphere CHEMISTRY 30S UNIT 2 PowerPoint Research Project Identify various industrial, environmental, and recreational applications of gases. Examples: SCUBA, anaesthetics, air bags, acetylene welding, propane appliances, hyperbaric chambers…
  • Gases & The Atmosphere CHEMISTRY 30S UNIT 2
  • Gases & The Atmosphere CHEMISTRY 30S UNIT 2 http://preparatorychemistry.com/Bishop_Boyles_frames.htm
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    • A
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    • D
    Section 13-1 Section 13.1 Assessment Boyle’s Law explains which relationship of properties in gases? A. pressure and volume B. amount and pressure C. temperature and volume D. volume and temperature
    • A
    • B
    • C
    • D
    Section 13-1 Section 13.1 Assessment Atoms are in their lowest energy state at what temperature? A. 0° Celsius B. 0° Fahrenheit C. –100° Celsius D. 0 kelvin
    • A
    • B
    • C
    • D
    Chapter Assessment 1 What does the combined gas law relate? A. pressure and temperature B. volume and pressure C. pressure, temperature, and volume D. pressure, temperature, volume, and amount
    • A
    • B
    • C
    • D
    Chapter Assessment 2 According to Charles’s law, if pressure and amount of a gas are fixed, what will happen as volume is increased? A. Temperature will decrease. B. Temperature will increase. C. Mass will increase. D. Mass will decrease.
    • A
    • B
    • C
    • D
    STP 1 If two variables are directly proportional, what happens to the value of one as the other decreases? A. increases B. decreases C. remains constant D. none of the above
    • A
    • B
    • C
    • D
    STP 2 What conditions represent standard temperature and pressure? A. 0.00°C and 0.00atm B. 1.00°C and 1.00atm C. 0.00°F and 1.00atm D. 0.00°C and 1.00atm