2.7.1: The Basics of Energy (Problems)
- Page ID
- 210672
PROBLEM \(\PageIndex{1}\)
A burning match and a bonfire may have the same temperature, yet you would not sit around a burning match on a fall evening to stay warm. Why not?
- Answer
-
The temperature of 1 gram of burning wood is approximately the same for both a match and a bonfire. This is an intensive property and depends on the material (wood). However, the overall amount of produced heat depends on the amount of material; this is an extensive property. The amount of wood in a bonfire is much greater than that in a match; the total amount of produced heat is also much greater, which is why we can sit around a bonfire to stay warm, but a match would not provide enough heat to keep us from getting cold.
PROBLEM \(\PageIndex{2}\)
Explain the difference between heat capacity and specific heat of a substance.
- Answer
-
Heat capacity refers to the heat required to raise the temperature of the mass of the substance 1 degree; specific heat refers to the heat required to raise the temperature of 1 gram of the substance 1 degree. Thus, heat capacity is an extensive property, and specific heat is an intensive one.
PROBLEM \(\PageIndex{3}\)
How much heat, in joules and in calories, must be added to a 75.0–g iron block with a specific heat of 0.449 J/g °C to increase its temperature from 25 °C to its melting temperature of 1535 °C?
- Answer
-
50,800 J
12,200 cal
PROBLEM \(\PageIndex{4}\)
How much heat, in joules and in calories, is required to heat a 28.4-g (1-oz) ice cube from −23.0 °C to −1.0 °C?
- Answer
-
1310 J
313 cal
PROBLEM \(\PageIndex{5}\)
How much would the temperature of 275 g of water increase if 36.5 kJ of heat were added?
- Answer
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31.7° C
PROBLEM \(\PageIndex{6}\)
If 14.5 kJ of heat were added to 485 g of liquid water, how much would its temperature increase?
- Answer
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7.15 °C
PROBLEM \(\PageIndex{7}\)
A piece of unknown substance weighs 44.7 g and requires 2110 J to increase its temperature from 23.2 °C to 89.6 °C.
- What is the specific heat of the substance?
- If it is one of the substances found in Table 8.1.1, what is its likely identity?
- Answer a
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\(C=\dfrac{0.711\:J}{g\:°C}\)
- Answer b
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Silicon
PROBLEM \(\PageIndex{8}\)
A piece of unknown solid substance weighs 437.2 g, and requires 8460 J to increase its temperature from 19.3 °C to 68.9 °C.
- What is the specific heat of the substance?
- If it is one of the substances found in Table 8.1.1, what is its likely identity?
- Answer a
-
\(C=\dfrac{0.390\:J}{g\:°C}\)
- Answer b
-
Copper
PROBLEM \(\PageIndex{9}\)
An aluminum kettle weighs 1.05 kg.
- What is the heat capacity of the kettle (Table 8.1.1)?
- How much heat is required to increase the temperature of this kettle from 23.0 °C to 99.0 °C?
- How much heat (in kJ) is required to heat this kettle from 23.0 °C to 99.0 °C if it contains 1.25 L of water (density of 0.997 g/mL and a specific heat of 4.184 J/g °C)?
- Answer a
-
\(C=\dfrac{0.897\:J}{g\:°C}\)
- Answer b
-
71580 J
- Answer c
-
467.86 kJ
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Contributors and Attributions
Paul Flowers (University of North Carolina - Pembroke), Klaus Theopold (University of Delaware) and Richard Langley (Stephen F. Austin State University) with contributing authors. Textbook content produced by OpenStax College is licensed under a Creative Commons Attribution License 4.0 license. Download for free at http://cnx.org/contents/85abf193-2bd...a7ac8df6@9.110).
- Adelaide Clark, Oregon Institute of Technology
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