Lecture Notes: Specific Heat Capacity

Learning Objectives

• Define heat capacity and specific heat capacity and differentiate between the two.
• Predict which substance will experience the greatest temperature change based on specific heat capacities.
• Calculate unknown variables using the specific heat equation.

Heat Capacity

• Definition: Amount of heat needed to raise the temperature of a substance by 1°C.
• Equation:
  
• Concept:
  • A small heat capacity leads to quick warming.
  • A high heat capacity allows absorption of more heat with less temperature increase.
  • Example: Metal pots (low heat capacity) vs. plastic handles (high heat capacity).
• Dependence:
  • Depends on material identity and quantity.
  • Greater mass substantiates greater heat.
  • Consistent comparison requires constant substance quantity.

Specific Heat Capacity

• Definition: Heat required to change the temperature of 1g of a substance by 1°C.
• Equation: q = mcΔT
  • Note: Capital “C” refers to heat capacity, lower case “c” to specific heat capacity.
  • Specific heat capacity allows calculation of an object's heat capacity based on another object of the same material but different mass.
• Properties:
  • Intensive property (does not depend on quantity).
  • Heat capacity is extensive (depends on quantity).
• Phase Dependence:
  • Different phases of the same substance can have different specific heat capacities.

Key Concepts

• Intensive vs. Extensive:
  • Specific heat capacity is intensive, while heat capacity is extensive.
• Example Calculation:
  • Exercise: Identifying which material will have the highest temperature upon heat absorption (solid gold).

Table: Specific Heats of Common Substances

• Helium (g): 5.193 J/g°C
• Water (l): 4.184 J/g°C
• Ethanol (l): 2.376 J/g°C
• Ice (s): 2.093 J/g°C
• Water Vapor (g): 1.864 J/g°C
• Nitrogen (g): 1.040 J/g°C
• Air (mixture): 1.007 J/g°C
• Oxygen (g): 0.918 J/g°C
• Aluminum (s): 0.897 J/g°C
• Carbon Dioxide (g): 0.853 J/g°C
• Argon (g): 0.522 J/g°C
• Iron (s): 0.449 J/g°C
• Copper (s): 0.385 J/g°C
• Lead (s): 0.130 J/g°C
• Gold (s): 0.129 J/g°C
• Silicon (s): 0.712 J/g°C

Examples

• Exercise 1: Solid gold will have the highest temperature increase when equal masses of water, gold, and iron are exposed to the same heat.
• Example 2: Calculation of final temperature of Aluminum when given heat and mass.

Additional Information

• The specific heat capacity is crucial to identifying materials and predicting behavior under thermal exposure.

Contributors

• Robert Belford (UA of Little Rock)
• Ronia Kattoum (UA of Little Rock)