Key Concepts What causes gas pressure in a closed container? What factors affect gas pressure? 3. How are the temperature, volume, and pressure of a gas related?

a. The result of a force distributed over an area. 1. Pressure a. The result of a force distributed over an area. b. Collisions between particles of a gas and the walls of the container cause the pressure in a closed container of gas. http://www.bbc.co.uk/staticarchive/1892d615d510908b1151d6a98e5d0966fc3d938d.gif

1. Pressure c. The SI unit of pressure is derived from SI units for force and area. 1). Force is measured in newtons (N). 2). Area is measured in square meters (m2). 3). The SI unit for pressure, the pascal (Pa), is equal to newtons per square meter. 4). One kilopascal (kPa) is equal to 1000 pascals.

a. Temperature b. Volume c. Number of its particles. 2. Factors That Affect Gas Pressure a. Temperature b. Volume c. Number of its particles.

2. Factors That Affect Gas Pressure Temperature 1). Raising the temperature of a gas will increase its pressure if the volume of the gas and the number of particles are constant. https://d2gne97vdumgn3.cloudfront.net/api/file/rNAHpnFQRF7qebsJKbzw

2. Factors That Affect Gas Pressure 2). Example: The firefighter is using a pressure gauge to check the air pressure in a tire on a firetruck.

2. Factors That Affect Gas Pressure Volume 1). Reducing the volume of a gas increases its pressure if the temperature of the gas and the number of particles are constant. http://2012books.lardbucket.org/books/principles-of-general-chemistry-v1.0/section_14/a433792ac2caa29995f55547b9d15918.jpg

2. Factors That Affect Gas Pressure Examples: Twist the cap onto a plastic bottle and then squeeze it. What happens? The volume of the plastic bottle begins to decrease. As the volume decreases, the particles of trapped air collide more often with the walls of the bottle. The pressure in the bottle increases.

2. Factors That Affect Gas Pressure 2). Examples: Movement of a muscle called the diaphragm changes the volume of your chest cavity. Inhaling Exhaling Diaphragm contracts. Rib cage is lifted up and out. Diaphragm relaxes. Rib cage moves down and in. Lungs Rib Cage Diaphragm

2. Factors That Affect Gas Pressure Number of Particles 1). Increasing the number of particles will increase the pressure of a gas if the temperature and the volume are constant. 2). The more particles there are in the same volume, the greater the number of collisions and the greater the pressure.

3. Charles’s Law French physicist Jacques Charles collected data on the relationship between the temperature and volume of gases. The graph of the data showed a direct relationship between the volume of a gas and the temperature of the gas. https://upload.wikimedia.org/wikipedia/commons/thumb/9/98/Jacques_Alexandre_C%C3%A9sar_Charles.jpg/200px-Jacques_Alexandre_C%C3%A9sar_Charles.jpg

Charles’s Law Charles extended the graph beyond the measured data to find the temperature that would produce a volume of 0 L. The temperature at the point where the line crossed the x-axis was –273.15°C.

equal to 0 K on the Kelvin temperature scale. 3. Charles’s Law This temperature is equal to 0 K on the Kelvin temperature scale. A temperature of 0 K is called absolute zero. https://s-media-cache-ak0.pinimg.com/736x/7d/06/05/7d0605d00013c75e00522f137779f9d2.jpg

3. Charles’s Law d. States that the volume of a gas is directly proportional to its temperature in kelvins if the pressure and the number of particles of the gas are constant. T1 and V1 – Before the temperature change T2 and V2 – After the temperature change

4. Boyle’s Law Robert Boyle described the relationship between the pressure and volume of a gas. The graph shows an inverse relationship between the volume of a gas and the pressure of the gas.

4. Boyle’s Law c. States that the volume of a gas is inversely proportional to its pressure if the temperature and the number of particles are constant. P1 and V1 - Before a change occurs. P2 and V2 - After a change occurs.

5. The Combined Gas Law The relationships described by Boyle’s law and Charles’s law can be described by a single law. The combined gas law describes the relationship among the temperature, volume, and pressure of a gas when the number of particles is constant.

5. The Combined Gas Law c. Examples: A cylinder that contains air at a pressure of 100 kPa has a volume of 0.75 L. The pressure is increased to 300 kPa. The temperature does not change. Find the new volume of air. Given: Work: Solve for: Answer:

5. The Combined Gas Law A gas has a volume of 5.0 L at a pressure of 50 kPa. What happens to the volume when the pressure is increased to 125 kPa? The temperature does not change. Given: Work: Solve for: Answer:

The Combined Gas Law 2. Gas stored in a tank at 273 K has a pressure of 388 kPa. The safe limit for the pressure is 825 kPa. At what temperature will the gas reach this pressure? Given: Work: Solve for: Answer:

The Combined Gas Law Given: Work: Solve for: Answer: 3. At 10ºC, the gas in a cylinder has a volume of 0.250 L. The gas is allowed to expand to 0.285 L. What must the final temperature be for the pressure to remain constant? (Hint: Convert using ºC + 273 = K.) Given: Work: Solve for: Answer:

5. The Combined Gas Law Balloons like this one are used by scientists to gather data about Earth’s atmosphere. The balloon is filled with hydrogen or helium. It carries a package of weather instruments up into the atmosphere.

The Combined Gas Law The gas laws explain the behavior of the gas in the balloon.

Assessment Questions What causes the pressure to increase if more gas particles are added to a closed container? an increase in the number of collisions between the gas and the container walls a decrease in the volume of the container a decrease in the size of each particle as the number of particles increases an increase in the number of collisions between air particles and the outside of the container

Assessment Questions What causes the pressure to increase if more gas particles are added to a closed container? an increase in the number of collisions between the gas and the container walls a decrease in the volume of the container a decrease in the size of each particle as the number of particles increases an increase in the number of collisions between air particles and the outside of the container ANS: A

Assessment Questions When first blown up, a balloon is firm because of the air pressure inside it. However, after time, the balloon becomes soft as the air pressure inside drops. What could have caused the air pressure to decrease? increase in air temperature decrease in the balloon's volume decrease in the number of air particles as they leaked out of the balloon a chemical reaction between the air particles and the balloon

Assessment Questions When first blown up, a balloon is firm because of the air pressure inside it. However, after time, the balloon becomes soft as the air pressure inside drops. What could have caused the air pressure to decrease? increase in air temperature decrease in the balloon's volume decrease in the number of air particles as they leaked out of the balloon a chemical reaction between the air particles and the balloon ANS: C

Assessment Questions A gas has a volume of 15 L, a temperature of 300 K, and an unknown initial pressure. Then, the gas expands to 30 L, remains at 300 K, and has a pressure of 300 kPa. What was the initial pressure of the gas? 150 kPa 600 kPa 330 kPa 570 kPa

Assessment Questions A gas has a volume of 15 L, a temperature of 300 K, and an unknown initial pressure. Then, the gas expands to 30 L, remains at 300 K, and has a pressure of 300 kPa. What was the initial pressure of the gas? 150 kPa 600 kPa 330 kPa 570 kPa ANS: B

Assessment Questions According to Charles’s law, the relationship between the temperature and the volume of a gas is direct. inverse. exponential. inverse square.

Assessment Questions According to Charles’s law, the relationship between the temperature and the volume of a gas is direct. inverse. exponential. inverse square. ANS: A

Assessment Questions 5. When the temperature of the gas in closed container is increased, the pressure increases. True False

Assessment Questions 5. When the temperature of the gas in closed container is increased, the pressure increases. True False ANS: T