Phase Changes
What phase change occurs when a solid changes into a liquid?
Melting
When a substance gains thermal energy, do its particles move faster or slower?
Faster
When a substance loses thermal energy, do its particles move faster or slower?
Slower
Temperature measures the average ______ energy of the particles in a substance.
Kinetic energy
What is the melting point of a substance?
The temperature at which it changes from a solid to a liquid as thermal energy is added.
What phase change occurs when a liquid changes into a gas?
Evaporation / Boiling
A solid gains thermal energy and its particles break out of their fixed positions and begin flowing past one another. What phase change occurred?
Melting
A liquid loses thermal energy until its particles become locked into fixed positions. What phase change occurred?
Freezing
Thermal energy is the ______ kinetic energy of all the particles in an object.
Total
What is the boiling point of a substance?
The temperature at which it changes from a liquid to a gas as thermal energy is added.
What phase change occurs when a gas changes into a liquid?
Condensation
A liquid gains enough thermal energy for particles at its surface to escape into the gas state. What is this called?
Evaporation
Water vapor cools and changes into drops of liquid water. What phase change occurred?
Condensation
If the temperature of water increases, what happens to the average motion of its molecules?
They move faster / have more kinetic energy.
At 100°C and low pressure (52 kPa), is water a liquid or a gas?
Gas
What phase change occurs when a liquid changes into a solid?
Freezing
Dry ice changes directly from a solid into a gas. What phase change is this?
Sublimation
Water vapor changes directly into solid frost without becoming a liquid first. What phase change is this?
Deposition
Two samples of water are at the same temperature, but one contains much more water. Which sample can have more thermal energy?
The larger sample / the sample with more particles.
At 100°C and high pressure (200 kPa), is water a liquid or a gas?
Liquid
Name BOTH phase changes that skip the liquid state.
Sublimation (solid → gas) and deposition (gas → solid)
Put these in the correct order:
a.) Particles move faster
b.) Substance gains thermal energy
c.) Possible change of state
b.) Substance gains thermal energy
a.) particles move faster
c.) possible change of state
Explain what happens to particles during freezing.
The particles lose thermal energy, slow down, and become locked into fixed positions where they can only vibrate.
Why can a large bowl of room-temperature water have more thermal energy than a small cup of boiling water?
Thermal energy depends on the total energy of all the particles, so the larger amount of water has many more particles.
As elevation increases, air pressure decreases. What happens to the boiling point of water?
The boiling point decreases.