Physics ch. 15

The specific heat capacity of steel is 450 J/kg⋅∘C. Select the correct equations that show that the amount of heat needed to raise the temperature of a 18-kg piece of steel from 0 ∘C to 100 ∘C is 810,000 J. 1. Q=cmΔT=(450J/kg⋅∘C)(18kg)(100∘C−0∘C)=810,000J 2. Q=cm/ΔT=(450J/kg⋅∘C)(18kg)/(100∘C−0∘C)=810,000J 3. Q=cΔT/m=(450J/kg⋅∘C)(100∘C−0∘C)/(18kg)=810,000J 4. Q=mΔT=(18kg)(100∘C−0∘C)=810,000J

1. Q=cmΔT=(450J/kg⋅∘C)(18kg)(100∘C−0∘C)=810,000J

When the temperature of a strip of iron is increased, the length of the strip ___________. 1. also increases 2. decreases in width as it gets longer 3. decreases 4. may increase or decrease

1. also increases

Suppose that we replace the aluminum with a mystery metal and repeat the experiment in the video. As in the video, the mass of the metal is the same as that of the water. Room temperature is about 20∘C before the start of the experiment. The water heats up to 40∘C, and the mystery metal heats up to 80∘C. Compared to that of water, the heat capacity of our mystery metal is 1. one-third as great. 2. two times greater. 3. three times greater. 4. the same. 5. half as great.

1. one-third as great. Given the same input of energy, the temperature of the metal increased three times as much as the temperature of the water. Therefore, the metal has one-third the heat capacity of water. (Recall that the heat Q delivered to a substance can be written Q = mc ΔT, where m is the mass of the substance and c is its heat capacity.)

Which one of these cites the lowest temperature? 1. 0° C 2. 270 K 3. 273K 4. 32°F

2. 270 K

Select the correct equations that show that the amount of heat needed is 1300 kcal ( 1300 Cal). 1. Q=cΔT=(1kcal/(kg⋅∘C))(20∘C)=1300kcal 2. Q=cmΔT=(1kcal/(kg⋅∘C))(65kg)(20∘C)=1300kcal 3. Q=cm/ΔT=(1kcal/(kg⋅∘C))(65kg)/(20∘C)=1300kcal 4. Q=cΔT/m=(1kcal/(kg⋅∘C))(20∘C)/(65kg)=1300kcal

2. Q=cmΔT=(1kcal/(kg⋅∘C))(65kg)(20∘C)=1300kcal

How does this compare with the heat needed to raise the temperature of the same mass of water through the same temperature difference? 1. This value is equal to the heat needed to raise the temperature of the same mass of water through the same temperature difference. 2. This value is less than the heat needed to raise the temperature of the same mass of water through the same temperature difference. 3. This value is greater than the heat needed to raise the temperature of the same mass of water through the same temperature difference.

2. This value is less than the heat needed to raise the temperature of the same mass of water through the same temperature difference.

Hot sand cools off faster at night than plants and vegetation. This indicates that the specific heat capacity for sand is ___________. 1. unrelated to rate of cooling 2. less than that of plants 3. more than that of plants 4. likely the same as that of plants

2. less than that of plants

The temperature of absolute zero is stated as ___________. 1. 32°C 2. 4 kelvin 3. -273°C 4. 273K

3. -273°C

The amount of heat needed to raise the temperature of 1 g of water by 1°C is ___________. 1. 1 newton 2. 1 joule or 1 calorie, as both are the same 3. 1 calorie 4. 1 joule

3. 1 calorie

Distinguish between a calorie and a Calorie. 1. A calorie is 1000 Calories. 2. A Calorie is measured by burning food, whereas a calorie is measured by digesting food. 3. A Calorie is 1000 calories. 4. A Calorie is a unit of temperature, whereas a calorie is a unit of energy.

3. A Calorie is 1000 calories.

When the temperature of ice-cold water is increased slightly, does it undergo a net expansion or a net contraction? 1. A combination of expansion (due to increased molecular motion) and contraction (due to crystal collapse) leads to a net expansion. 2. Expansion 3. Contraction 4. Neither contraction nor expansion

3. Contraction

How is the energy value of foods determined? 1. The food is fed to a python and the energy released is measured. 2. The foods are chemically broken down into their constituent molecules that have known energy values. 3. The food is burned and the energy released is measured. 4. The food is digested by microbes and the energy released is measured.

3. The food is burned and the energy released is measured.

Which of these has the highest specific heat capacity? 1. Soil 2. Silver 3. Water 4. Iron

3. Water

Select the correct equation that shows that this is equivalent to about 5400 kJ . 1. (1300kcal)(4190kJ/kcal)=5447kJ 2. (1300kcal)/(4.19kcal/kJ)=5447kJ 3. (1300kcal)/(4190kcal/kJ)=5447kJ 4. (1300kcal)(4.19kJ/kcal)=5447kJ

4. (1300kcal)(4.19kJ/kcal)=5447kJ

Which one of these is largest amount of energy? 1. 10 calories 2. 100 calories 3. 5 joules 4. 1 Calorie

4. 1 Calorie

Water is most dense at ___________. 1. less than 0°C 2. 0°C 3. 100°C 4. 4°C

4. 4°C

Which generally expands more for an equal increase in temperature: solids or liquids? 1. Solids generally expand more than liquids. 2. Solids and liquids generally do not expand when heated. 3. Solids and liquids generally expand the same. 4. Liquids generally expand more than solids.

4. Liquids generally expand more than solids.

Northeastern Canada and much of Europe receive about the same amount of sunlight per unit area. Why, then, is Europe generally warmer in the winter? 1. The ocean creates clouds over Europe that act as a blanket. 2. The low specific heat of frozen tundra in northeastern Canada holds onto its internal energy longer than the thawed soils of Europe. 3. The cold ocean absorbs heat from the cold European landmass. 4. The gulf stream carries warm, high heat capacity water past the west coast of Europe.

4. The gulf stream carries warm, high heat capacity water past the west coast of Europe.

When we speak about heat we refer to ___________. 1. transfer of kinetic energy 2. work 3. temperature 4. energy in transit

4. energy in transit