Energy Review #2 (Includes Calculations)

How much heat is required to raise the temperature of a 5.45-g sample of iron from 25.0^oC to 79.8^oC? (The heat capacity of iron is 0.450 J/g*^oC)

• 2.41 J

• 299 J

• 664 J

• 804 J

• 134 J

Tags

NGSS.HS-PS3-1

NGSS.HS-PS3-4

The same amount of heat is added to both 45.0 g of copper (heat capacity = 0.20 J/g*^oC) and 45.0 g of aluminum (0.89 J/g*^oC). Which metal undergoes the smallest change in temperature?

• Aluminum will have the smallest change in temperature.

• Copper will have the smallest change in temperature.

• Both metals will have the same change in temperature, because their masses are equal.

• This cannot be determined without knowing the initial temperature of the metal.

• None of these are true.

Tags

NGSS.HS-PS3-4

A 22.1-g piece of aluminum is heated to 82.4^oC and dropped into an insulated cup containing water initially at 22.3^oC. The temperature of the water increases to 25.8^oC. What is the mass of the water? (heat capacity of Al = 0.89 J/g*^oC and water = 4.18 J/g*^oC)

• 76.1 g

• 2,050 g

• 2.30 g

• 1.11 kg

• none of these

A 47.4 g sample of a metal is heated to 95.2^oC and placed into a calorimeter containing 120.0 g of water. The final temperature of the water is 24.5^oC. What is the identity of the metal? (C_H2O = 4.18 J/g*^oC)

• Aluminum (C = 0.89 J/g*^oC)

• Iron (C = 0.45 J/g*^oC)

• Copper (C = 0.20 J/g*^oC)

• Lead (C = 0.14 J/g*^oC)

• None of these

Challenge Problem: 224.5 g of a solid is at its melting point of 30.0^oC. It is melted by adding it to 425 g of water at 85.1^oC. The water temperature decreases to 30.0^oC. Calculate the heat of fusion (ΔH_fus) of this solid.

• ΔH_fus = 122 J/g

• ΔH_fus = 218 J/g

• ΔH_fus = 436 J/g

• ΔH_fus = 650 J/g

• Cannot solve without knowing the heat capacity of the solid.

Challenge Problem: 30.0 g of water at 9^oC is mixed with 50.0 g of water at 66^oC. What is the final temperature of the mixture?

• 38^oC

• 45^oC

• 152^oC

• 348^oC

• -216^oC

If 5.0 kJ of heat is added to a 15.5-g sample of water at 10^oC, the water is ___.

• boiling

• all completely vaporized

• frozen solid

• decomposed

• still a liquid

On a cold winter day, a steel metal fence post feels colder than a wooden fence post that is the same size because ___.

• the heat capacity of the steel is higher than the heat capacity of the wood

• the heat capacity of the steel is lower than the heat capacity of the wood

• steel has the ability to resist a temperature change better than wood.

• the mass of steel is less than the wood so it loses heat faster

• all of these statements are true

In the lab, you mix two solutions (each originally at the same temperature) and the temperature of the resulting solution decreases. What is true?

• This chemical reaction is releasing energy and is exothermic.

• This chemical reaction is absorbing energy and is exothermic.

• This chemical reaction is releasing energy and is endothermic.

• This chemical reaction is absorbing energy and is endothermic.

• None of these are true.

What would be the effect on the particles if more heat is supplied to the system?

• They would slow down
• They would stop moving
• They would speed up
• There would be no effect

Tags

NGSS.HS-PS1-5

NGSS.HS-PS3-4