Lecture Notes: Specific Heat Capacity

Learning Objectives

• Define heat capacity and specific heat capacity.
• Differentiate between heat capacity and specific heat capacity.
• Determine which substances will have the greatest temperature change based on specific heat capacities.
• Calculate unknown variables using the specific heat equation.

Heat Capacity

• Definition: The amount of heat needed to raise the temperature of a substance by 1°C.
• Equation:
  • C = q / ΔT
  • Units: Energy/Temperature
• Understanding:
  • Heat capacity reflects a substance's ability to resist temperature changes.
  • Substances with smaller heat capacities heat up quickly.
  • Example: Metal pots (low heat capacity) heat up faster than plastic handles (high heat capacity).
• Dependence: Depends on material identity and quantity.
  • More mass = more heat capacity.
  • Comparison of substances requires equal mass considerations.

Specific Heat Capacity

• Definition: Heat required to change the temperature of 1 gram of a substance by 1°C.
• Equation: q = mcΔT
  • c = q(J) / [m(g) * ΔT(K)]
• Key Points:
  • Specific heat capacity is an intensive property (does not depend on quantity).
  • Heat capacity is extensive (depends on quantity).
  • Doubling mass doubles heat capacity.
  • Some texts use "s" for specific heat capacity.
• Units: J/g°C
• Comparison: Allows comparison of substances on a per gram basis.*

Specific Heat of Common Substances (at 25°C and 1 bar)

• Water (H2O, l): 4.184 J/g°C
• Iron (Fe, s): 0.449 J/g°C
• Gold (Au, s): 0.129 J/g°C
• Ice (H2O, s): 2.093 J/g°C at 10°C
• Ethanol (C2H6O, l): 2.376 J/g°C
• Aluminum (Al, s): 0.897 J/g°C

Exercise and Examples

• Exercise 1: Determine which material (water, gold, or iron) will have the highest temperature given equal mass and heat:
  • Answer: Gold, due to the lowest specific heat capacity.
• Example 2: Calculate final temperature of 10.0 g aluminum when 100.0 J is added:
  • Use specific heat equation.

Contributors

• Robert Belford (University of Arkansas at Little Rock)
• Ronia Kattoum (University of Arkansas at Little Rock)

Note: Specific heat capacity depends on the phase of the substance (solid, liquid, gas).