1. Specific Heat
Calorimetry

2. Calculating Heat Transferred
Q = mCT
Q = amount of heat transferred
m = mass of substance
C = specific heat capacity of the substance.
T = temperature change = Tfinal – Tinitial

3. Calorimeter
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4. Another calorimeter
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5. Heat in Chemical Reactions
Changes in heat energy are measured by
The “universe” is contained in a styrofoam cup.
The “enviroment” is the water.****
The “system” is whatever we put in the water.
calorimetry

6. Energy lost = Energy gained
Calorimetry
Energy lost = Energy gained
Difficult to monitor the “system.”
Easy to monitor the “environment” – that’s the water!
Energy lost/gained by environment = Energy gained/lost by system

7. Exothermic – the temperature of the environment increased.
Calorimetry
10 grams of NaOH are dissolved in 100 g of water. The temperature of the water increases from 22C to 30C.
Was the dissolving process endothermic or exothermic & how do you know?
Exothermic – the temperature of the environment increased.

8. Dissolving What’s happening when the NaOH dissolves? Add H2O
Close together. Not interacting with H2O.
Pulled apart & interacting with H2O.

9. Calorimetry Q = mCT Q = energy (joules) M = mass (grams)
Calculate the energy released by the NaOH in the previous problem as it dissolved in the water. Energy lost by NaOH = Energy gained by water. Easier to calculate from H2O perspective.
Q = mCT
Q = energy (joules)
M = mass (grams)
C = specific heat capacity (Table B)
T = temperature change = Tf - Ti

10. Calorimetry & Q = mCT
The temperature of the water increased from 22C to 30C.
30C -22C = 8C = T
What mass? Well, the temperature change was for the water, so you want the mass of the water. m = 100 g.
Same goes for specific heat capacity. We’re going to calculate the heat absorbed by the water. CH20 = 4.18J/g

11. Q = mCT
Q = 100 g X 4.18 J/g X 8C
Q = 3344 Joules.

12. Expressing Heat Changes
The heat content of a system at constant pressure is the same as a property called
Heat released or absorbed (Q) by a reaction at constant pressure is the same as a change in enthalpy (rH),
therefore, Q = rH.
ENTHALPY