Chapter 14 Gas Laws Pressure Volume and Temperature

Chapter 14: Gas Laws: Pressure, Volume, and Temperature NEXT

Basic Terminology Review of terms used to describe the properties and behavior of gases. MAIN MENU NEXT

Opening thoughts… Have you ever: Had a soda bottle spray all over you? Baked (or eaten) a nice, fluffy cake? These are all examples of gases at work! MAIN MENU PREVIOUS NEXT

Properties of Gases You can predict the behavior of gases based on the following properties: Pressure Volume Amount (moles) Temperature Lets review each of these briefly… MAIN MENU PREVIOUS NEXT

You can predict the behavior of gases based on the following properties: Pressure Volume Amount (moles) Temperature MAIN MENU PREVIOUS NEXT

Pressure is defined as the force the gas exerts on a given area of the container in which it is contained. The SI unit for pressure is the Pascal, Pa. • If you’ve ever inflated a tire, you’ve probably made a pressure measurement in pounds (force) per square inch (area). MAIN MENU PREVIOUS NEXT

You can predict the behavior of gases based on the following properties: Pressure Volume Amount (moles) Temperature MAIN MENU PREVIOUS NEXT

Volume is the three-dimensional space inside the container holding the gas. The SI unit for volume is the cubic meter, m 3. A more common and convenient unit is the liter, L. Think of a 2 -liter bottle of soda to get an idea of how big a liter is. MAIN MENU PREVIOUS NEXT

You can predict the behavior of gases based on the following properties: Pressure Volume Amount (moles) Temperature MAIN MENU PREVIOUS NEXT

Amount (moles) Amount of substance is tricky. As we’ve already learned, the SI unit for amount of substance is the mole, mol. Since we can’t count molecules, we can convert measured mass to the number of moles, n, using the molar mass. By definition, one mole of a substance contains approximately 6. 022 x 1023 particles of the substance. You can understand why we use mass and moles! MAIN MENU PREVIOUS NEXT

You can predict the behavior of gases based on the following properties: Pressure Volume Amount (moles) Temperature MAIN MENU PREVIOUS NEXT

Temperature is the measurement of heat…or how fast the particles are moving. Gases, at room temperature, have a lower boiling point than things that are liquid or solid at the same temperature. Remember: Not all substance freeze, melt or evaporate at the same temperature. Water will freeze at zero degrees Celsius. However Alcohol will not freeze at this temperature. MAIN MENU PREVIOUS NEXT

How do they all relate? Some relationships of gases may be easy to predict. Some are more subtle. Now that we understand the factors that affect the behavior of gases, we will study how those factors interact. MAIN MENU PREVIOUS NEXT

Boyle’s Law, describes the relationship between pressure and volume of gases. MAIN MENU NEXT

Boyle’s Law n n MAIN MENU PREVIOUS volume pressure This law is named for Charles Boyle, who studied the relationship between pressure, p, and volume, V, in the mid-1600 s. Boyle determined that for the same amount of a gas at constant temperature, results in an inverse relationship: when one goes up, the other comes down. NEXT

What does Boyle’s Law mean? A decrease in volume will result in increased pressure. MAIN MENU PREVIOUS NEXT

Boyle’s Law at Work… Doubling the pressure reduces the volume by half. Conversely, when the volume doubles, the pressure decreases by half. MAIN MENU PREVIOUS NEXT

Charles’ Law, describes the relationship between volume and temperature of gases. MAIN MENU NEXT

Charles’ Law n n volume MAIN MENU PREVIOUS temperature This law is named for Jacques Charles, who studied the relationship volume, V, and temperature, T, around the turn of the 19 th century. This defines a direct relationship: With the same amount of gas he found that as the volume increases the temperature also increases. If the temperature decreases than the volume also decreases. NEXT

What does Charles’ Law mean? An increase in temperature results in increased volume. MAIN MENU PREVIOUS NEXT

Charles’ Law at Work… As the temperature increases, the volume increases. Conversely, when the temperature decreases, volume decreases. MAIN MENU PREVIOUS NEXT

Gay-Lussac's Law Gay-Lussac’s law states that the pressure of a fixed amount of gas varies directly with the temperature when the volume remains constant.

Gay-Lussac's Law (cont. )

The Combined Gas Law The combined gas law states the relationship among pressure, temperature, and volume of a fixed amount of gas.

Avogadro's Law • Volume of gas is proportional to the amount (moles) of gas V α n • equal volumes of all gases, at the same temperature and. pressure, have the same number of molecules".

The Ideal Gas An ideal gas is defined as one the particles of which are point masses, showing no interactions (forces of attractions or repulsions) at all

The Ideal Gas Law The ideal gas law describes the physical behavior of an ideal gas in terms of pressure, volume, temperature, and amount. The ideal gas constant is represented by R and is 0. 0821 L • atm/mol • K when pressure is in atmospheres.