Understanding Heat and Energy Changes in Chemistry

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Amount of heat energy needed to raise the
temp of 1 ml of a substance 1
°C
For water the specific heat is 4.19 J/g °C, but it
is differenct for different substances
It takes 4.19 J to raise the temp of 1 g of water
1 °C
Every substance has a different specific heat
 
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Heat released or absorbed can be calculated by
multiplying three factors
Heat = specific heat x mass x temp change
    
q = c x m x 
Δt
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The specific heat of water is 4.19 J/ g 
C. How
much heat is needed to warm 350g of water
from 25
 C to 75
 C?
If 178 J of heat is needed to increase the
temperature of a 20g piece of copper metal
from 25
 C to 48
 C, what is the specific heat of
copper?
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Heat of vaporization (
H
VAP
)
  
energy required
to change one gram of a substance from liquid
to gas.
For water 2260J/g
Q = 
H
VAP
 m
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The heat of vaporization of water is 2260J/g
.
How much heat must be supplied to evaporate
50g of water?
How much heat is required to evaporate 150.g
of a substance at its boiling point if it has a
H
vap
= 987 J/g?
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Heat of fusion (
H
fus
)
 energy required to
change one gram of a substance from solid to
liquid.
For water 340 J/g
Q = 
H
fus
 m
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The heat of fusion of ice at 0
°C is 340J/g. How
much heat is needed to change 75g of ice at
0°C to a liquid at the same temperature?
The heat of fusion of water at 0
°C is 340J/g.
How much heat is released when 250g of
water changes to ice at 0°C?
 
 
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How much heat is needed to change 100g of
water at 50
C to steam at 120
C? The specific
heat of water is 4.19 J/g 
C, the specific heat of
steam is 1.7 J/g 
C, and the heat of
vaporization of water is 2260 J/g.
How much heat must be released as 50g of
water at 25
C to ice at -10
C? The specific
heat of water is 4.19 J/g 
C, the specific heat of
ice is 2.1 J/g 
C, and the heat of fusion fro
water is 340 J/g.
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Explore the concepts of heat, specific heat, phase change, and energy calculations in chemistry. Learn how to calculate heat, specific heat values for different substances, and the energy needed for phase changes like vaporization and fusion. Practice problems and examples are provided to enhance understanding.


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  1. Calculating Heat

  2. Specific Heat Amount of heat energy needed to raise the temp of 1 ml of a substance 1 C For water the specific heat is 4.19 J/g C, but it is differenct for different substances It takes 4.19 J to raise the temp of 1 g of water 1 C Every substance has a different specific heat

  3. Table of Specific Heats

  4. Calculating Heat When Substance in One Phase Heat released or absorbed can be calculated by multiplying three factors Heat = specific heat x mass x temp change q = c x m x t

  5. Practice The specific heat of water is 4.19 J/ g C. How much heat is needed to warm 350g of water from 25 C to 75 C? If 178 J of heat is needed to increase the temperature of a 20g piece of copper metal from 25 C to 48 C, what is the specific heat of copper?

  6. Heat and Phase Change (Evaporation) Heat of vaporization ( HVAP) energy required to change one gram of a substance from liquid to gas. For water 2260J/g Q = HVAPm

  7. Practice The heat of vaporization of water is 2260J/g. How much heat must be supplied to evaporate 50g of water? How much heat is required to evaporate 150.g of a substance at its boiling point if it has a Hvap= 987 J/g?

  8. Energy and Phase Change Heat of fusion ( Hfus) energy required to change one gram of a substance from solid to liquid. For water 340 J/g Q = Hfusm

  9. Examples The heat of fusion of ice at 0 C is 340J/g. How much heat is needed to change 75g of ice at 0 C to a liquid at the same temperature? The heat of fusion of water at 0 C is 340J/g. How much heat is released when 250g of water changes to ice at 0 C?

  10. Practice How much heat is needed to change 100g of water at 50 C to steam at 120 C? The specific heat of water is 4.19 J/g C, the specific heat of steam is 1.7 J/g C, and the heat of vaporization of water is 2260 J/g. How much heat must be released as 50g of water at 25 C to ice at -10 C? The specific heat of water is 4.19 J/g C, the specific heat of ice is 2.1 J/g C, and the heat of fusion fro water is 340 J/g.

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