This document discusses heat and heat capacity. It defines heat as a transfer of energy associated with a temperature change and notes that heat capacity is the amount of heat required to change an object's temperature by 1°C or 1K. The document outlines two types of heat capacity: specific heat capacity, which is the heat capacity per gram of a substance, and molar heat capacity, which is the heat capacity per mole of a gas. Molar heat capacity can be measured at constant pressure (Cp) or constant volume (Cv).

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2. Topic:
Heat And Heat Capacity
Presented by: Mehak Shabbir
BCH172003
BS-Chemistry 6th (A)
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3. Contents
v Heat
v Heat Capacity
Ø Specific Heat Capacity
Ø Molar Heat Capacity
qMolar Heat Capacity At Constant Pressure
qMolar Heat Capacity At Constant Volume
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4. • A form of exchange or transfer of energy when temperature of system changes
• It is a disordered form of energy
Ø More heat transfers to bottom than top when we place pan on stove
• It is denoted by symbol (q)
• It can be positive or negative number
Ø Heat is released into surroundings → negative ( q < 0 )
Ø Heat is absorbed into surroundings → positive ( q > 0 )
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5. Cont...
• Units:
Ø S.I unit of heat is Joule (J)
Ø Frequently measured in Calorie (cal)
Ø Sometimes measured in British thermal units (Btu)
• Example:
A hot cup of tea becomes cold when placed at room temperature.
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6. Heat Capacity
• The amount of heat required to change the temperatue of system by 1oC or 1K
• It is denoted by symbol (C)
• Mathematicaly,
C is heat capacity
q is heat energy
T is temperature
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7. Cont...
• When ∆T = 1oC then C = q
• Unit:
q = Joule (J) or Calorie (cal)
T = Kelvin (K) or (oC)
So,
C = J / K
C = cal / oC
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8. Cont...
• It depends on mass (m)
Ø If mass is greater then heat capacity will be large
Ø If mass is smaller then heat capacity will be small
• Hence, heat capacity is an extensive property
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9. Types Of Heat Capacity
There are two types of heat capacity
1. Specific heat capacity
2. Molar heat capacity
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10. 1. Specific Heat Capacity
• The amount of heat given to 1gm solid or liquid to change the temperature by 1oC
or 1K
• It is the heat capacity for solid or liquid
• It is denoted by symbol (S)
• Mathematicaly,
S = q / m∆T
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11. Cont...
• If m = 1gm and ∆T = 1oC then S = q
• Also
q = Sm∆T
• Units:
S = Jgm-1K-1
S = Calgm-1oC-1
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12. 2. Molar Heat Capacity
• The amount of heat required for any gas of 1mol to change in temperature by 1oC or
1K
• It is the heat capacity for gas
• It is denoted by symbol (Cm )
• Mathematicaly,
Cm = q / n∆T
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13. Cont...
• Units:
Jmol-1K-1 or Calmol-1oC-1
• It is an intensive property
• Moalr heat capacity can be represented in two forms
Ø At constant pressure
Ø At constant volume
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14. Cont...
q Molar Heat Capacity At Constant
Pressure (Cp)
• Represented as
Ø Cp = q / m∆T
• Unit:
Cp = Jmol-1K-1
q Molar Heat Capacity At Constant
Volume (Cv)
• Represnted as
Ø Cv = q / m∆T
• Unit:
Cv = Jmol-1K-1
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