How much heat in joules is required to heat a 42 g sample of aluminum from 74 F

Question

How much heat in joules is required to heat a 42 g sample of aluminum from 74 F to 149 F? (The specific heat capacity of aluminum is 0.903 J/(gC).)

Express your answer using two significant figures.

E =

The wattage of an appliance indicates the average power consumption in watts (W), where 1 W=1J/s.

(Figure 1)

Part A

Global warming refers to the rise in average global temperature due to the increased concentration of certain gases, called greenhouse gases, in our atmosphere. Earth's oceans, because of their high heat capacity, can absorb heat and therefore act to slow down global warming.
How much heat would be required to warm Earth's oceans by 1.0 C? Assume that the volume of Earth's oceans is 137×107km3 and that the density of seawater is 1.03 g/cm3. Also assume that the specific heat capacity of seawater is the same as that of water.

Express your answer using two significant figures.

Part A

What is the difference in the number of kJ of energy consumed per month between a refrigeration unit that consumes 621 W and one that consume 856 W ? (Assume 30.0 days in one month and 24.0 hours per day.)

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Part B

If electricity costs $0.15 per kWh, what is the monthly cost difference to operate the two refrigerators?

Express your answer using four significant figures.

  J  

E =

The wattage of an appliance indicates the average power consumption in watts (W), where 1 W=1J/s.

Earth's oceans moderate temperatures by absorbing heat during warm periods.

(Figure 1)

Part A

Global warming refers to the rise in average global temperature due to the increased concentration of certain gases, called greenhouse gases, in our atmosphere. Earth's oceans, because of their high heat capacity, can absorb heat and therefore act to slow down global warming.
How much heat would be required to warm Earth's oceans by 1.0 C? Assume that the volume of Earth's oceans is 137×107km3 and that the density of seawater is 1.03 g/cm3. Also assume that the specific heat capacity of seawater is the same as that of water.

Express your answer using two significant figures.

E =   J  

Part A

What is the difference in the number of kJ of energy consumed per month between a refrigeration unit that consumes 621 W and one that consume 856 W ? (Assume 30.0 days in one month and 24.0 hours per day.)

E =   kJ  

SubmitRequest Answer

Part B

If electricity costs $0.15 per kWh, what is the monthly cost difference to operate the two refrigerators?

Express your answer using four significant figures.

cost =   $  

  J  

Explanation / Answer

1.

Mass of Al = 42 g.

Specific heat of Al = 0.903 J/g.0C

Change in temperature = 149 - 74 = 75 0F = 5 * ( 75 - 32 ) / 9 0C = 23.9 0C

Heat change = mass * specific heat * change in temperature

q = 42 * 0.903 * 23.9 = 906.4 J

2.

Mass of 1 cm3 of sea water = 1.03 g.

but, 1 km = 1000 m = 1000 * 100 cm = 105 cm

1 km3 = (105)3 = 1015 cm3

SO, mass of 1 km3 of sea water = 1.03 * 1015 g.

So,

Heat required = mass * specific heat * change in temperature

q = 1.03 * 1015 * 4.184 * 1

q = 4.3 * 1015 J

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