Chem quiz U. 7

1. Explain the effect of:

a. Adding or removing gas to a constant volume. What happens to the pressure? Is this a
direct or indirect relationship?
Adding gas is a direct relationship. The more gas added, the higher the pressure inside the
container is.

b. Increasing or decreasing volume of a gas. What happens to the pressure? Is this a direct or
indirect relationship?
The pressure will increase with decreasing volume. Pressure and volume and in an
indirect relationship with each other: as one thing goes up, the other goes down.

c. Raising or lowering temperature. What happens to the pressure? Is this a direct or
indirect relationship?
As temperature is increased pressure increases. This is a direct relationship.

2. Why are gases easy to compress?
There are large spaces between gas particles that allows them to be confined to smaller places
and compressed.

3. If the temperature is constant, what change in volume would cause the pressure of an enclosed
gas to increase by a factor of 4?
Decrease the volume of the gas to ¼ of its size, decrease by a factor of 4

4. Assuming the temperature is held constant, how could you increase the pressure inside a
container by a factor of 3?
Decrease the volume to 1/3 of its value, decrease by a factor of 3

5. Explain why heating a contained gas that is held at a constant volume increases its pressure.
The increased KE of the particles causes collisions to occur more frequently and with more
force.

6. If a gas is compressed from 4L to 1L, and the temperature remains constant, what happens to
the pressure?
The pressure will quadruple. (x4)

In a phase diagram, what is the triple point?
The triple point is the point in which all phases, S, L, G, are in equilibrium with each
other

1. Both liquid and gas particles can slide past one another, this is known as the ability to?

flow.

2. The forces that keep liquid particles together are called?

Intermolecular forces of attraction

3. Particles in the liquid state have ____ IM attractive forces than in the gas state?

Greater

4. When a pressure is applied to a gas, its volume will decrease. Therefore, gases are said to be?

Compressible

5. Because liquid particles are already so close together, they will not decrease significantly in
volume when pressure is applied to them. Liquids are said to be?

Slightly compressible

6.______s the conversion of liquid to gas below a substance’s boiling point?

Evaporation

7. Evaporation only occurs at the____ of the liquid?

Surface

8. As the temperature of a liquid increases, the rate of evaporation would?
Increase. This is because higher temperatures provide more energy to the molecules, allowing more of them to escape into the vapor phase.

9. However, evaporation is a cooling process, because the particles with the _____ kinetic
energy are removed from the liquid.

Highest

10. When 2 opposite reactions occur at the same rate, the system is in a state of?

Equilibrium

11. For a liquid in a closed container, equilibrium occurs when the rate of evaporation equals the
rate of?

Condensation

12. Equilibrium is a ____ process, meaning that both reactions are still occurring.

Dynamic

13. What is evaporation?
A liquid converting to a gas below the substance’s boiling point.

14. Why does evaporation lower the temperature of a liquid?
The particles with the highest KE leaves the liquid, leaving the lower KE particles behind. (Like
taking the fastest runner out of a marathon race – this leaves the slower runners behind.)

15. Explain the difference in the evaporation of a contained liquid and an uncontained liquid.
The particles in a contained liquid cannot escape (Equilibrium is reached)
The particles in an uncontained liquid can diffuse (No equilibrium is reached)

16. Explain why increasing the temperature of a liquid increases its rate of evaporation.
Increasing temperature increases the KE of the particles and allows some particles to overcome
the IM forces of attraction.