Chapter 23: Change of Phase

An air sample contains 25% of the amount of water vapor it is capable of holding. The air's relative humidity is

25%

Write a short paragraph on boiling. How does a pressure cooker cook food faster?

Boiling is the change of phase from liquid to gas that occurs beneath the surface in the liquid. The gas forms bubbles that rise to the surface and escape. A pressure cooker cooks food faster by the temperature increasing. Since it has tight fit lid that doesn't allow vapor to escape, the vapor builds up inside so the pressure on the liquid increases which prevents boiling.

Write a short paragraph on why evaporation is considered a cooling process.

Evaporation is the change of phase from liquid to gas. Evaporation is considered a cooling process because some molecules gain speed at the expense of others that lose speed. Those that evaporate are gainers while losers remain behind in the liquid and effectivelty lower the average kinetic energy.

True of False. When ice changes to water at 0 degrees C, energy is released.

False

True or False. The process of changing from a liquid state to a solid state is condensation.

False

True or False. The three common phases of matter are mass, density, and volume.

False

What is regelation? What does it have to do with ice skating and making snowballs?

Regelation is the phenomenon of ice melting under pressure and freezing again when the pressure is reduced. When you compress the snow in your hands, you cause a slight melting which helps to build the snowball. Originally people thought, an ice skate's pressure lowered the freezing point of ice.

On which day will the amount of water vapor in the air be greater, a summer day at 100% humidity or a winter day at 100% humidity?

The summer day

True of False. It is possible for a thin wire suspended between heavy weights to pass through a block of ice.

True

True of False. When steam changes to water at 100 degrees C, energy is released.

True

Which will melt a bigger hole in block of ice - a red-hot mail tossed on it or a red-hot piece of wood of the same mass and temperature?

Wood

Evaporation is a cooling process and condensation is

a warming process

Food cooked in boiling water in the mountains cooks more slowly than cooked at sea level. If the temperature under the pot is increased, the food will cook

at the same rate as before

If you want to cook boiled eggs while in the mountains, you should

boil the eggs for a longer time

Ice is put in a cooler to cool the food stored there. In order to speed up the cooling process, you should

crush the ice

Condensation occurs when matter changes from a

gas to a liquid

When water freezes, it

gives off energy

Steam burns are more damaging than burns caused by boiling water because steam

has more energy per kilogram than boiling water

As atmospheric pressure increases, the boiling temperature of a liquid

increases

At high altitudes, the boiling point of water

is lower

When boiling water in the mountains, the time needed to reach the boiling point is

less than at sea level

The reason pressure cookers cook food faster is that they

raise the cooking temperature of the food

Morning dew on the grass is a result of

slow moving molecules condensing on the grass

When heat is added to boiling water, the temperature of the boiling water

stays the same

Pigs roll in the mud

to keep their skin wet so evaporation can occur

The cooling effect inside a refrigerator is produced by

vaporizing the refrigeration liquid

When snow forms in clouds, the surrounding air

warms

In order to walk barefoot on hot coals without harming your feet, less energy would get to your feet if your feet were

wet