Chapter 5 Matter and Heat

An ideal frictionless engine absorbs heat from a source at 400 K and exhausts heat to a reservoir at 300 K. Its efficiency is a. 25 percent b. 33 percent c. 75 percent d. 133 percent

a

On the molecular level, heat is a. kinetic energy b. potential energy c. rest energy d. all of these, in proportions that depend on the circumstances

a

The physics of a refrigerator most closely resembles the physics of a. a heat engine b. the melting of ice c. the freezing of water d. the evaporation of water

a

The volume of a gas sample is increased while its temperature is held constant. The gas exerts a lower pressure on the walls of its container because its molecules strike the walls a. less often b. with lower velocities c. with less energy d. with less force

a

The working substance (or refrigerant) used in most refrigerators is a a. gas that is easy to liquefy b. gas that is hard to liquefy c. liquid that is easy to solidify d. liquid that is hard to solidify

a

Buoyancy occurs because, as the depth in a fluid increases, the fluid's a.pressure increases b.pressure decreases c.density increases d.density decreases

a.pressure increases

Heat transfer in a vacuum can occur by a.radiation only b.convection only c.radiation and convection only d.radiation, convection, and conduction

a.radiation only

The pressure of the earth's atmosphere at sea level is due to a.the gravitational attraction of the earth for the atmosphere b.the heating of the atmosphere by the sun c.the fact that most living things constantly breathe air d.evaporation of water from the seas and oceans

a.the gravitational attraction of the earth for the atmosphere

A heat engine takes in heat from a source at one temperature and turns a. all of it into work b. some of it into work and rejects the rest to a reservoir at a lower temperature c. some of it into work and rejects the rest to a reservoir at the same temperature d. some of it into work and rejects the rest to a reservoir at a higher temperature

b

A wooden plank 200 cm long, 30 cm wide, and 40 mm thick floats in water with 10 mm of its thickness above the surface. The mass of the plank is a. 1.8 kg b. 18 kg c. 24 kg d. 176 kg

b

At a given temperature a. the molecules in a gas all have the same average speed b. the molecules in a gas all have the same average energy c. light gas molecules have lower average energies than heavy gas molecules d. heavy gas molecules have lower average energies than light gas molecules

b

Heat is absorbed by the refrigerant in a refrigerator when it a. melts b. vaporizes c. condenses d. is compressed

b

If a heat engine that exhausts heat to a reservoir at 400 K is to have an efficiency of 33 percent, it must take in heat from a source at a minimum of a. 133 K b. 449 K c. 532 K d. 600 K

b

In any process the maximum amount of heat that can be converted to mechanical energy a. depends on the amount of friction present b. depends on the intake and exhaust temperatures c. depends on whether kinetic or potential energy is involved d. is 100 percent

b

Oxygen boils at −183°C. The Fahrenheit equivalent of this temperature is a. −215°F b. −297°F c. −329°F d. −361°F

b

The Celsius equivalent of a temperature of 120°F is a. 35°C b. 49°F c. 67°C d. 88°C

b

When 1 kg of steam at 200°C loses 3 MJ of heat, the result is a. ice b. water and ice c. water d. water and steam

b

When 20 kJ of heat are removed from 1.2 kg of ice originally at −5°C, its new temperature is a. −18°C b. −23° C c. −26° C d. −35° C

b

The density of freshwater is 1.00 g/cm3 and that of seawater is 1.03 g/cm3. A ship will float a.higher in freshwater than in seawater b.lower in freshwater than in seawater c.at the same level in freshwater and seawater d.any of the above, depending on the shape of its hull

b.lower in freshwater than in seawater

An ice cube whose center consists of liquid water is floating in a glass of water. When the ice melts, the level of water in the glass a.rises b.remains the same c.falls d.any of the above, depending on the relative volume of water inside the ice cube

b.remains the same

A 2-kg brick has the dimensions 7.5 cm x 15 cm x 30 cm. The pressure the brick exerts on the ground when standing on its smallest face is a. 0.0178 Pa b. 0.0225 Pa c. 178 Pa d. 225 Pa

c

A 3-kg pine board is 20 cm wide, 2 cm thick, and 2 m long. The density of the board is a. 240 kg/m3 b. 267 kg/m3 c. 375 kg/m3 d. 469 kg/m3

c

A refrigerator gives off a. less heat than it absorbs from its contents b. the same amount of heat it absorbs from its contents c. more heat than it absorbs from its contents d. Any of these choices could be correct, depending on the circumstances

c

At which of the following temperatures would the molecules of a gas have twice the average kinetic energy they have at room temperature, 20°C? a. 40°C b. 80°C c. 313°C d. 586°C

c

Food cooks more rapidly in a pressure cooker than in an ordinary pot with a loose lid because a. the pressure forces heat into the food b. the high pressure lowers the boiling point of water c. the high pressure raises the boiling point of water d. the tight lid keeps the heat inside the cooker

c

If the pressure on 10 m3 of air is increased from 200 kPa to 800 kPa, the new volume of air will be a. 1.25 m3 b. 1.67 m3 c. 2.5 m3 d. 40 m3

c

The greater the entropy of a system of particles, a. the less the energy of the system b. the greater the energy of the system c. the less the order of the system d. the greater the order of the system

c

When evaporation occurs, the liquid that remains is cooler because a. the pressure on the liquid decreases b. the volume of the liquid decreases c. the slowest molecules remain behind d. the fastest molecules remain behind

c

Which of the following statements is not correct? a.Matter is composed of tiny particles called molecules. b.These molecules are in constant motion, even in solids. c.All molecules have the same size and mass. d.The differences between the solid, liquid, and gaseous states of matter lie in the relative freedom of motion of their respective molecules.

c.All molecules have the same size and mass.

The fluid at the bottom of a container is a.under less pressure than the fluid at the top b.under the same pressure as the fluid at the top c.under more pressure than the fluid at the top d.any of these, depending upon the circumstances

c.under more pressure than the fluid at the top

A frictionless heat engine can be 100 percent efficient only if its exhaust temperature is a. equal to its input temperature b. less than its input temperature c. 0°C d. 0 K

d

An object suspended from a spring scale is lowered into a pail filled to the brim with water, and 4 N of water overflows. The scale shows that the object weighs 6 N in the water. The weight in air of the object is a. 2 N b. 4 N c. 6 N d. 10 N

d

In any process the maximum amount of mechanical energy that can be converted to heat a. depends on the amount of friction present b. depends on the intake and exhaust temperatures c. depends on whether kinetic or potential energy is involved d. is 100 percent

d

Lead melts at 330°C. On the absolute scale this temperature corresponds to a. 57 K b. 362 K c. 571 K d. 603 K

d

The second law of thermodynamics does not lead to the conclusion that a. on a molecular level, order will eventually become disorder in the universe b. all the matter in the universe will eventually end up at the same temperature c. no heat engine can convert heat into work with 100 percent efficiency d. the total amount of energy in the universe, including rest energy, is constant

d

The temperature of a gas sample in a container of fixed volume is raised. The gas exerts a higher pressure on the walls of its container because its molecules a. lose more PE when they strike the walls b. lose more KE when they strike the walls c. are in contact with the walls for a shorter time d. have higher average velocities and strike the walls more often

d

When 400 kJ of heat is added to 12 kg of water at 2°C, its final temperature is a. 5.9°C b. 7.9°C c. 11.7°C d. 17.9°C

d

When a vapor condenses into a liquid, a. its temperature rises b. its temperature falls c. it absorbs heat d. it gives off heat

d

A person stands on a very sensitive scale and inhales deeply. The reading on the scale a.increases b.does not change c.decreases d.any of the above, depending on how the expansion of the person's chest compares with the volume of air inhaled

d.any of the above, depending on how the expansion of the person's chest compares with the volume of air inhaled

Molecular motion is not responsible for a.the pressure exerted by a gas b.Boyle's law c.evaporation d.buoyancy

d.buoyancy

One gram of steam at 100°C causes a more serious burn than 1 g of water at 100°C because the steam a.is less dense b.strikes the skin with greater force c.has a higher specific heat d.contains more energy

d.contains more energy

At constant pressure, the volume of a gas sample is directly proportional to a.the size of its molecules b.its Fahrenheit temperature c.its Celsius temperature d.its absolute temperature

d.its absolute temperature

Two thermometers, one calibrated in °F and the other in °C, are used to measure the same temperature. The numerical reading on the Fahrenheit thermometer a.is less than that on the Celsius thermometer b.is equal to that on the Celsius thermometer c.is greater than that on the Celsius thermometer d.may be any of these, depending on the temperature

d.may be any of these, depending on the temperature

Absolute zero may be regarded as that temperature at which a.water freezes b.all gases become liquids c.all substances become solid d.molecular motion in a gas would be the minimum possible

d.molecular motion in a gas would be the minimum possible

Heat transfer in a gas can occur by a.radiation only b.convection only c.radiation and convection only d.radiation, convection, and conduction

d.radiation, convection, and conduction