Chapter 17: Change of Phase Flashcards
Steam burns are more damaging than burns caused by boiling water because steam
gives up change of phase energy when it condenses and has more energy per kilogram than boiling water
When a gas is changed to a liquid state, the gas
releases energy
As atmospheric pressure is increased, the boiling temperature of a liquid
goes up
If we slowly pump out all the air over a bowl of water until it is in a vacuum,
it will boil, then freeze
Food in a pressure cooker is cooked faster because of the
higher temperatures reached in a sealed container.
Adding pressure to ice causes ice to
melt
Near the top of a mountain, water in an open pot boils at
a lower temperature than at sea level
The food in a refrigerator is cooled by
vaporization of the refrigerating fluid
Compared to a glass of ice water with ice in it, on a warm day a glass of pure ice-cold water without ice will warm up
faster
If you heat an ice bucket of water for several hours until only a small amount of ice remains, the temperature of water will be
0° C
When warm air rises, it
expands and cools
If you add heat for 35 minutes to a pan with 2 kgs of 100°C water in it the temperature of the remaining water will be
100°C
How many joules does it takes to vaporize 1 gram of water?
2255 J (sometimes rounded up to 2260 J)
When water in the vapor phase condenses to liquid in the air, the surrounding air
warms
When the air pressure is lowered,
it takes less heat to boil water
The change of phase from liquid to gaseous?
Evaporation
The change of phase from solid to gaseous, bypassing the liquid phase?
Sublimation
The change of phase from gaseous to liquid?
Condensation
Rapid evaporation that takes place within a liquid as well as at its surface?
Boiling
The process of melting under pressure and the subsequent refreezing when the pressure is removed?
Regelation
A device that transfers heat out of a cool environment and into a warm environment?
Heat pump
The amount of energy required to change a unit mass of a substance from solid to liquid (and released in the reversed process).
Latent heat of fusion
The amount of energy required to change a unit mass of a substance from liquid to gas (and released in the reverse process).
Latent heat of vaporization
A solid must _______ energy to _______.
A solid must absorb energy to melt.
A liquid must _______ energy to _______.
A liquid must absorb energy to vaporize.
A gas must _______ energy to ________.
A gas must release energy to liquify.
A liquid must _______ energy to ________.
A liquid must release energy to solidify.
When H2O in the vapor phase condenses, is the surrounding air warmed or cooled?
Warmed. The change of phase is from vapor to liquid, which releases energy, so the surrounding air is warmed.
One calorie is equal to how many joules?
4.187 joules
Heat of ___________ is either the energy required to separate molecules from the liquid phase or the energy released when gas condenses to the liquid phase.
vaporization
Heat of _______ is either the energy needed to separate molecules from the solid phase or the energy released when bonds form in a liquid that change it to the solid phase.
fusion
______ has more potential energy because the molecules are relatively free of each other and are not bound together as in the liquid phase.
Steam
How much energy is transferred when 1 g of steam at 100 degrees C condenses to water at 100 degrees C?
540 calories of energy. One gram of steam at 100 degrees C transfers 540 calories of energy when it condenses to become water at same temperature.
How much energy is transferred when 1 g of boiling water at 100 degrees C cools to ice water at 0 degrees C?
100 calories. One gram of boiling water transfers 100 calories when it cools 100 degrees C to become ice water.
How much energy is transferred when 1 g of ice water at 0 degrees C freezes to ice at 0 degrees C?
80 calories. One gram of ice water at 0 degrees C transfers 80 calories to become ice at 0 degrees C.
How much energy is transferred when 1 g of steam at 100 degrees C turns to ice at 0 degrees C?
720 calories. One gram of steam at 100 degrees C transfers to the surroundings 720 calories to become ice at 0 degrees C.
If 4 g of boiling water is poured onto a cold surface and 1 g rapidly evaporates, if evaporation takes 540 calories from the remaining 3 g of water and no other heat transfer takes place, what will be the temperature of the remaining 3 g?
0 degrees C. The remaining 3 g will turn into 0 degree C ice.
When snow forms in clouds, the surrounding air is ________.
warmed (the change of phase is from gas to solid which releases energy).
Which involves the greatest number of calories: a) Condensing 1 g of 100 degree C steam to 100 degree C water; b) Cooling 1 g of 100 degree C water to 1 gram of 0 degree C ice; c) Cooling 1 g of 0 degree C ice to near absolute zero; d) All about the same
a) Condensing 1 g of 100 degree C steam to 100 degree C water, which takes 540 calories.
Ice is put in a picnic cooler. To speed up the cooling of cans of beverage, it is important that the ice: a) melts; b) is prevented from melting; c) be in large chunks; d) None of the above
a) melts; For each gram of ice that melts, 80 calories is taken from the beverage.
Boiling point is lower with
lower atmospheric pressure
The process of boiling: a) cools the water being boiled; b) depends on atmospheric pressure; c) is a change of phase below the water surface; d) All of the above
d) All of the above
