Edexcel IGCSE Physics 复习笔记 5.2.4 Specific Heat Capacity

• How much the temperature of a system increases depends on:
  • The mass of the substance heated
  • The type of material
  • The amount of energy put in to the system

   

• The energy put in is in the form of thermal energy

• The specific heat capacity, c of a substance is defined as:

The amount of energy required to raise the temperature of 1 kg of the substance by 1 °C

• Different substances have different specific heat capacities
  • If a substance has a low specific heat capacity, it heats up and cools down quickly (ie. it takes less energy to change its temperature)
  • If a substance has a high specific heat capacity, it heats up and cools down slowly (ie. it takes more energy to change its temperature)

   

Low vs high specific heat capacity

• The amount of energy needed to raise the temperature of a given mass by a given amount can be calculated using the equation:

Change in thermal energy  = Mass × Specific heat capacity  × Change in temperature

ΔQ = mcΔT

• Where:
  • ΔQ = change in thermal energy, in joules (J)
  • m = mass, in kilograms (kg)
  • c = specific heat capacity, in joules per kilogram per degree Celsius (J/kg °C)
  • ΔT = change in temperature, in degrees Celsius (°C)

   

Step 1: Write down the known quantities

• • Mass, m = 0.48 kg
  • Change in temperature, ΔT = 0.7 °C
  • Specific heat capacity, c = 4200 J/kg °C

   

Step 2: Write down the relevant equation 

ΔQ = mcΔT

Step 3: Calculate the thermal energy transferred by substituting in the values

ΔQ = (0.48) × (4200) × (0.7) = 1411.2

Step 4: Round the answer to 2 significant figures

ΔQ = 1400 J