Chpt. 17 HW

Rank the boiling-water temperatures in different locations. a) Death Valley b) sea level c) Denver, CO (the "mile-high city")

A, B, C

Why do you feel uncomfortably warm on a hot and humid day? a) Cooling sweat does not evaporate well in humid air. b) It's not the humidity that makes you uncomfortable - it's the heat. c) Humidity condensing on your body heats you. d) Humidity condensing on your body cools you less.

a) Cooling sweat does not evaporate well in humid air.

Do the molecules in a liquid all have about the same speed, or do they have a wide variety of speeds? a) Molecules in a liquid vibrate but they do not move from one place to another. b) Some are slow and some are fast. c) They all move at the speed of sound in the liquid. d) All molecules in a liquid have the average speed.

b) Some are slow and some are fast.

What happens when you heat ice that is at 0∘C? a) The temperature stays constant forever. b) The temperature stays constant until all the ice is melted. c) The temperature increases until all of the ice is melted. d) The temperature increases forever.

b) The temperature stays constant until all the ice is melted.

Boiling can occur in cold water when _________. a) sub-zero temperatures are achieved b) pressure is sufficiently lowered c) concentration and physics come together d) pressure is sufficiently increased

b) pressure is sufficiently lowered lowered pressure at high altitudes decrease the boiling point of a liquid. boiling depends not only on temperature, but on pressure as well.

What happens when you heat ice that is at -40∘C? a) The temperature stays constant. b) The temperature increases forever. c) The temperature increases until the ice reaches its melting point.

c) The temperature increases until the ice reaches its melting point.

Changes of phase most always require _________. a) electron transfer b) a condition of thermal equilibrium c) a transfer of energy d) an absence of molecular contact

c) a transfer of energy

Why doesn't energy added to boiling water increase the temperature of the water? a) Boiling is a cooling process, so energy is removed as quickly as it is added. b) Boiling is a cooling process, so condensing steam inside bubbles cools the liquid as fast as it is heated. c) Boiling is a heating process, so added energy is expelled as fast as it enters. d) Boiling is a heating process, so condensing steam inside the bubbles cools the liquid as fast as it is heated.

a) Boiling is a cooling process, so energy is removed as quickly as it is added.

What are the four common phases of matter? a) Solid, liquid, gas, plasma b) Solid, liquid, suspension, plasma c) Earth, air, fire, water d) Solid, liquid, gas, foam

a) Solid, liquid, gas, plasma phases depend on temperature and pressure on the matter. Phase changes require a transfer of energy.

Cite two reasons why firewalkers don't burn their wetted feet when they walk barefoot on red-hot coals. a) Hot coals have a low conductivity, and water on wet feet releases a lot of energy as it vaporizes. b) Hot coals have a high conductivity, and water on wet feet releases a lot of energy as it vaporizes. c) Hot coals have a high conductivity, and water on wet feet absorbs a lot of energy as it vaporizes. d) Hot coals have a low conductivity, and water on wet feet absorbs a lot of energy as it vaporizes.

d) Hot coals have a low conductivity, and water on wet feet absorbs a lot of energy as it vaporizes. Energy that would normally go into burning skin instead does into changing the phase of water on the skin. The energy converts the water into vapor, an insulating layer between the feet and coals.

Distinguish between humidity and relative humidity. a) Humidity is the mass of water per unit volume. Relative humidity is the mass per unit volume in an adjacent volume. b) Humidity is the mass of water per unit volume. Relative humidity is the mass of water per unit area. c) Humidity is the mass of water per unit area of your skin. Relative humidity is the ratio of humidity to maximum humidity. d) Humidity is the mass of water per unit volume. Relative humidity is the ratio of the amount of water in the air to the maximum amount of water the air could contain.

d) Humidity is the mass of water per unit volume. Relative humidity is the ratio of the amount of water in the air to the maximum amount of water the air could contain.

Does increased atmospheric pressure increase or decrease the boiling point of water? Why? a) Decrease. Higher pressure expands the bubbles that form. b) Decrease. Higher pressure collapses the bubbles that form. c) Increase. Higher pressure expands the bubbles that form. d) Increase. Higher pressure collapses the bubbles that form.

d) Increase. Higher pressure collapses the bubbles that form.

What happens when you heat water that is at 100∘C? a) The temperature increases forever. b) The temperature increases until all of the water is boiled. c) The temperature stays constant forever. d) The temperature stays constant until all the water is boiled.

d) The temperature stays constant until all the water is boiled.

Why does increasing the temperature of a solid make it melt? a) Increasing the temperature increases molecular vibrations until attractive forces can no longer hold the molecules in one place. b) Increasing the temperature causes molecular cohesion until the solid melts. c) Increasing the temperature causes little pockets of sublimated gas to form, thereby breaking molecular bonds and melting the solid. d) Increasing the temperature increases pressure in the solid, which causes it to melt.

a) Increasing the temperature increases molecular vibrations until attractive forces can no longer hold the molecules in one place.

Does a solid release energy or absorb energy when it changes into a liquid? When it sublimes into a gas? a) Absorb, release b) Absorb, absorb c) Release, absorb d) Release, release

b) Absorb, absorb

Does a liquid release energy or absorb energy when it changes into a gas? Into a solid? a) Release, release b) Absorb, release c) Absorb, absorb d) Release, absorb

b) Absorb, release

What is condensation? Is condensation a warming or cooling process? a) Condensation is when a gas becomes a liquid. It is a cooling process. b) Condensation is when a gas becomes a liquid. It is a warming process. c) Condensation is when a gas becomes a solid. It is a warming process. d) Condensation is when a gas becomes a solid. It is a cooling process.

b) Condensation is when a gas becomes a liquid. It is a warming process.

Why does decreasing the temperature of a liquid make it freeze? a) Cooling stops all vibrational motion, thereby allowing molecules to lock together as a solid. b) Cooling slows molecular motion until attractive forces between molecules can hold them in place. c) Cooling causes the liquid to shrink in volume, which allows the molecules to bond together. d) Cooling causes contraction, which increases internal pressure and pushes the molecules together.

b) Cooling slows molecular motion until attractive forces between molecules can hold them in place.

Distinguish between evaporation and boiling. a) Evaporation happens in the bulk of the liquid, whereas boiling occurs at the surface. b) Evaporation happens at a liquid surface, whereas boiling occurs in the bulk of the liquid. c) Evaporation is a heating process, whereas boiling is a cooling process. d) Evaporation is a cooling process, whereas boiling is a heating process.

b) Evaporation happens at a liquid surface, whereas boiling occurs in the bulk of the liquid.

Why is evaporation a cooling process? a) Molecules break bonds as they leave the liquid. Molecules with broken bonds are cooler. b) When the fastest molecules leave during evaporation, the slower, cooler ones remain. c) When the slowest molecules leave during evaporation, the faster, cooler ones remain. d) When the fastest molecules leave during evaporation, the slower, warmer ones remain.

b) When the fastest molecules leave during evaporation, the slower, cooler ones remain.

What happens to the water pressure at the bottom of a geyser when some of the water above gushes out? What is the result? a) As water rushes out, the pressure on the remaining water is increased. This pushes water into the geyser, thereby refilling it. b) As water rushes out, the pressure on the remaining water is reduced. This sucks in water to refill the geyser. c) As water rushes out, the pressure on the remaining water is reduced, so the water boils. d) As water rushes out, the pressure on the remaining water is increased, so the water boils.

c) As water rushes out, the pressure on the remaining water is reduced, so the water boils.

What is sublimation? Is it a heating or cooling process? a) Sublimation is when the slowest molecules at the surface of a solid have escape velocity and leave the solid. It is a cooling process for the solid left behind. b) Sublimation is when the slowest molecules at the surface of a solid have escape velocity and leave the solid. It leaves behind the faster, warmer molecules. c) Sublimation is when the fastest molecules at the surface of a solid have escape velocity and leave to become a gas. It leaves behind the slower, cooler molecules. d) Sublimation is when the fastest molecules at the surface of a solid have escape velocity and leave the solid. It is a heating process for the solid left behind.

c) Sublimation is when the fastest molecules at the surface of a solid have escape velocity and leave to become a gas. It leaves behind the slower, cooler molecules.

What cooks food faster in a pressure cooker? a) The higher pressure cooks the food faster. b) The bubbles created by boiling are full of steam that cooks the food faster. c) The higher temperature of boiling water under pressure cooks the food faster. d) The violent convection heats and cooks the food faster.

c) The higher temperature of boiling water under pressure cooks the food faster.

What happens when you heat water that is at 0∘C? a) The temperature increases forever. b) The temperature does not change. c) The temperature increases until it reaches 100∘C.

c) The temperature increases until it reaches 100∘C.

Describe the condensation, evaporation, and heat flows that happen in a refrigerator. a) Liquid condenses inside the refrigerator, absorbing energy. Gas evaporates outside the refrigerator, releasing energy. b) Liquid evaporates inside the refrigerator, releasing energy. Gas condenses outside the refrigerator, absorbing energy. c) Liquid condenses inside the refrigerator, releasing energy. Gas evaporates outside the refrigerator, absorbing energy. d) Liquid evaporates inside the refrigerator, absorbing energy. Gas condenses outside the refrigerator, releasing energy.

d) Liquid evaporates inside the refrigerator, absorbing energy. Gas condenses outside the refrigerator, releasing energy.

Why is a steam burn more damaging than a burn from boiling water at the same temperature? a) Steam penetrates deeply into the skin, whereas water does not. b) Water molecules in steam have more kinetic energy than those in water at the same temperature. c) Steam contacts your entire skin, whereas water droplets touch only a small part of your skin. d) The steam releases considerable energy when it condenses to liquid on the skin.

d) The steam releases considerable energy when it condenses to liquid on the skin.