Specific Heat and Heat Capacity

Heat Capacity 

Heat Capacity:  the amount of the heat required to raise the temperature of a sample of a substance by 1 ◦ C. This does NOT take into account the mass of a substance.

            Symbol: C

Unit:       J/◦ C

Equation: q= (C) (ΔT)

q = heat

C= heat capacity

ΔT = T_final  – T_inital  (change in temperature)

Example: A sample of CaCl₂ was placed in a calorimeter and 6790 J of energy were released by the sample and absorbed by the calorimeter as the instrument’s temperature rose from 25 ◦C to 60 ◦ C. What is the heat capacity of the calorimeter?

 q = (C) (Δ T)

 6790J  = (C) (60-25 ◦C)

 6790 J  =  (C) (35  ◦C)

6790J/35 ◦C = C

194 J/ ◦C = C

Specific Heat

Specific Heat: the amount of the heat required to raise the temperature of a 1 gram of a substance by 1 ◦ C. This DOES take into account the mass of a substance.

Symbol: s

Unit:       J/g ◦ C

Equation: q = (m) (s) (Δ T)

q = heat

m= mass (in grams)

s= specific heat

ΔT = T_final  – T_inital  (change in temperature)

Example:  How much energy is required to increase the temperature of 140.5 g of iron (specific heat = 0.444 J/g  ◦ C) from 12 degrees Celsius to 40 degrees Celsius. Report your answer in kJ units.

 

q = (m) (s) (ΔT)

q = (140.5 g) (0.444 J/g  ◦ C) (40-12)

q= 1747 J

1747 J/1000 = 1.747 kJ

 

Relating Specific Heat and Heat Capacity

 

Specific heat and heat capacity vary for different substances. The higher the specific heat of the substance, the more energy it takes for its temperature to rise. Additionally, the temperature change is minimal for such a substance as it gains or loses heat.

 

Did You Know? The surface of the Earth is comprised mainly of water. Good thing! The high specific heat of water make it more difficult for large swings in temperature and help keep the planet’s climate regulated and conducive to life.