Gas Laws: Pressure, Volume, and Hot Air NEXT

Introduction Welcome! This interactive lesson will introduce three ways of predicting the behavior of gases: Boyle’s Law, Charles’ Law, and the Ideal Gas Law. Never heard of them? Don’t worry– that’s the purpose of this lesson! NEXTPREVIOUS

Navigation Throughout this lesson, you will use buttons at the bottom right corner of the page to navigate. Takes you to the next page Takes you to the previous page Takes you to the Main Menu NEXTPREVIOUS

Main Menu Basic Terminology Boyle’s Law Charles’ Law Ideal Gas Law Review of all four lessons Review Lesson 1 Lesson 2 Lesson 3 Lesson 4

Lesson 1: Basic Terminology This lesson reviews terms used to describe the properties and behavior of gases. NEXT MAIN MENU

Opening thoughts… Have you ever: Seen a hot air balloon? NEXTPREVIOUS MAIN MENU

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

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

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

Pressure 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). NEXTPREVIOUS MAIN MENU

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

Volume 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. (OK, how big two of them are…) NEXTPREVIOUS MAIN MENU

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

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 (in kg) to the number of moles, n, using the molecular or formula weight of the gas. By definition, one mole of a substance contains approximately x particles of the substance. You can understand why we use mass and moles! NEXTPREVIOUS MAIN MENU

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

Temperature 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. NEXTPREVIOUS MAIN MENU Water will freeze at zero degrees Celsius. However Alcohol will not freeze at this temperature.

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. NEXTPREVIOUS MAIN MENU

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. PREVIOUS MAIN MENU Let’s go!

Lesson 2: Boyle’s Law This lesson introduces Boyle’s Law, which describes the relationship between pressure and volume of gases. NEXT MAIN MENU

Boyle’s Law This law is named for Charles Boyle, who studied the relationship between pressure, p, and volume, V, in the mid-1600s. 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. NEXTPREVIOUS MAIN MENU pressure volume

What does Boyle’s Law mean? Suppose you have a cylinder with a piston in the top so you can change the volume. The cylinder has a gauge to measure pressure, is contained so the amount of gas is constant, and can be maintained at a constant temperature. A decrease in volume will result in increased pressure. Hard to picture? Let’s fix that! NEXTPREVIOUS MAIN MENU

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

Boyle’s Law Video charles-gay-lussacs-laws-pressure- volume-and-temperature- relationships.html PREVIOUS MAIN MENU

Lesson 3: Charles’ Law This lesson introduces Charles’ Law, which describes the relationship between volume and temperature of gases. NEXT MAIN MENU

Charles’ Law 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. NEXTPREVIOUS MAIN MENU volume temperature

What does Charles’ Law mean? Suppose you have that same cylinder with a piston in the top allowing volume to change, and a heating/cooling element allowing for changing temperature. The force on the piston head is constant to maintain pressure, and the cylinder is contained so the amount of gas is constant. An increase in temperature results in increased volume. Hard to picture? Let’s fix it (again)! NEXTPREVIOUS MAIN MENU

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

Absolute zero A temperature of 0 K is equivalent to degrees C

Absolute zero continued.. No scientist has ever produced a temp of absolute zero….. As a gas cools to a temperature near 0 K, the gas changes to a liquid, a solid, or sometimes a condensate.

Charles’s Law law-gas-pressure-and-temperature- relationship.html PREVIOUS MAIN MENU

Combined Gas Law Combining Boyle’s Law with Charles’s Law  P 1 V 1 / T 1 = P 2 V 2 / T 2

Practice Problem 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. P 1 V 1 / T 1 = P 2 V 2 / T 2

Practice Problem continued.. What info are you given?  P 1 = 100 kPa P 2 = 300 kPa V 1 = 0.75L What unknown are you solving for?  V 2 P 1 V 1 / T 1 = P 2 V 2 / T 2 Cancel out the variable that does not change and rearrange the expression to solve for V 2

Practice Problem answer V 2 = 100 kPa x 0.75L/300 kPa = 0.25 L

Mission complete! You have completed the lessons and review. Congratulations! You should now have a better understanding of the properties of gases, how they interrelate, and how to use them to predict gas behavior. Please click on the button below to reset the lesson for the next student. Thanks! Return to Title Slide