# CH.5 a-b - Gases & Laws

The student will investigate and understand that the phases of matter are explained by kinetic theory and forces of attraction between particles. Key concepts include:
a) pressure, temperature, and volume;
b) partial pressure and gas laws.

Bloom's Levels:  Analyze; Understand

### BIG IDEAS

• Pressure, temperature, number of particles, and volume are interrelated.
• Behavior of gases is governed by equations called "gas laws."

• I can explain why an empty water bottle collapses if left outside on a cold night.

### UNDERSTANDING THE STANDARD

• Atoms and molecules are in constant motion.
• The phase of a substance depends on temperature and pressure.
• Temperature is a measurement of the average kinetic energy in a sample. There is a direct relationship between temperature and average kinetic energy.
• The kinetic molecular theory is a mdoel for predicting and explaining gas behavior.
• Gases have mass and occupy space. gas particles are in constant, rapid, random motion and exert pressure as they collide with the walls of their containers. gas molecules with the lightest mass travel fastest. relatively large distances separate gas particles from each other.
• Equal volumes of gases at the same temperature and pressure contain an equal number of particles. Pressure units include atm, kPA, and mm Hg.
• An ideal gas does not exist, but this cocnept is used to model gas behavior. A real gas exists, has intermolecular forces and particle volume, and can change states. The Ideal Gas Law states that PV = nRT.
• The pressure and volume of a sample of a gas at constant temperature are inversely proportional to each other (Boyle's Law: P1V1 = P2V2).
• At constant pressure, the volume of a fixed amount of gas is directly proportional to its absolute temperature (Charles' Law: V1/T1 = V2/T2).
• The Combined Gas Law (P1V1/T1 = P2V2/T2) relates pressure, volume, and temperature of a gas.
• The sum of the partial pressures of all the components in a gas mixture is equal to the total pressure of a gas mixture (Dalton's law of partial pressures).

### ESSENTIALS

In order to meet this standard, it is expected that students will

a)  explain the behavior of gases and the relationship between pressure and volume (Boyle’s Law), and volume and temperature (Charles’ Law).

b)  solve problems and interpret graphs involving the gas laws.

### KEY VOCABULARY

Avogadro's law, Boyle's law, Charles's law, combined gas law, Dalton's law of partial pressure, Gay-Lussac's law, Graham's law of diffusion, ideal gas constant (R), ideal gas law, kinetic molecular theory, molar volume

Updated: Nov 19, 2017