Teehan Science 8 Enriched Objective Today-Understand relationship between pressure and volume. Do Now- Describe the particles of a gas compared to solid and liquid. Think of 3 everyday uses of gases.

Have you ever put air in your tires? How do you check how much air they have?

Kinetic Molecular theory The kinetic molecular theory is an explanation of how particles in matter behave. We have already discussed this.  Small particles make up matter  Constant random motion  Particles collide with other particles, with other objects and with the container  No energy is lost when particles collide, they just change direction

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. What is the energy of motion? NEXTPREVIOUS MAIN MENU Kinetic Energy

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

17 Boyle’s Law Boyle’s Law states that the pressure of a gas is inversely related to its volume when T and n are constant. if volume decreases, the pressure increases.

We are going to discover Boyles Law

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

21 Learning Check For a cylinder containing helium gas indicate if cylinder A or cylinder B represents the new volume for the following changes (n and T are constant). 1) pressure decreases 2) pressure increases

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

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

1) A container holds 50.0 mL of nitrogen at 25° C and a pressure of 736 mm Hg. What will be its volume if the temperature increases by 35° C?

2) A sample of oxygen occupies a volume of 160 dm3 at 91° C. What will be volume of oxygen when the temperature drops to 0.00° C?

3) A sample of hydrogen has an initial temperature of 50.° C. When the temperature is lowered to -5.0° C, the volume of hydrogen becomes 212 cm3. What was the initial volume of the hydrogen in dm3 ?