Specific Heat Capacity (Copy)

 1. Core Concept: What is Specific Heat Capacity?

• Definition: The specific heat capacity of a substance is the amount of heat energy required to raise the temperature of 1 kg of the substance by 1°C.
• Symbol: c
• Unit: J/kg°C

 Formula:

Q = mcΔT

Where:

• Q = energy supplied (in joules, J)
• m = mass of the substance (in kilograms, kg)
• c = specific heat capacity (J/kg°C)
• ΔT = temperature change (°C)

Rearranged for SHC:
c = Q / (m × ΔT)

 2. Objective of the Experiment

• To determine the specific heat capacity of a solid (e.g. metal block) or liquid (e.g. water) by measuring temperature change and energy input.

 3. Apparatus Required

 4. Step-by-Step Method: For Metal Block

1. Measure mass of metal block using digital balance.
   → Record in kg
2. Insert immersion heater and thermometer into holes drilled in block.
3. Wrap block in insulating material and cover top.
4. Record initial temperature.
5. Turn on power supply and start joulemeter or record V, I, and time.
6. Stir occasionally to ensure even heating.
7. After 5–10 minutes, record final temperature.
8. Use formula:
   → If joulemeter: c = Q / (m × ΔT)
   → If not: Q = IVt, then c = Q / (m × ΔT)

For Water (in Beaker):

Same steps as above, with:

• Use a beaker or calorimeter instead of block
• Measure mass of water only using balance
• Use stirrer to mix water evenly

 5. Sample Calculation

Given:

• Mass = 1.00 kg
• Initial temp = 20°C
• Final temp = 42°C
• Energy input Q = 92400 J

Then:
ΔT = 42 – 20 = 22°C
c = Q / (m × ΔT) = 92400 / (1.00 × 22) = 4200 J/kg°C

✔️ Specific heat capacity = 4200 J/kg°C

 6. Data Table Example

→ Use this to plot temperature vs time and determine ΔT over total heating period.

 7. Graphical Analysis

• Plot: Temperature (°C) vs Time (s)
• Use gradient if power is constant:
  

  Slope tells you how fast temperature rises → indicates rate of energy gain
  Can be used to calculate SHC indirectly

✔️ If graph is used:
Q = Power × Time → estimate ΔT from graph

 8. Common Errors and How to Fix Them

 9. Variables

 10. Improvement Suggestions

• Use lagging jacket or polystyrene insulation
• Cover top of beaker/block with lid or foil
• Use digital data logger for temperature recording
• Calibrate thermometer or use temp probe
• Take multiple readings and average final temperature

 11. ATP-Style Questions

 12. Exam Tips

• Use Joulemeter if possible – simplest way to measure Q
• Quote Q = mcΔT or Q = IVt before substitution
• Convert:
  → g to kg: divide by 1000
  → minutes to seconds: ×60
• Give units and significant figures:
  → SHC usually to 2 or 3 sig figs
• Label axes:
  → “Time / s”, “Temperature / °C”

Final sentence example:

“Using a joulemeter gives a total energy of 95000 J, and the temperature of the 1.2 kg metal block increased by 20°C. Therefore:
c = 95000 / (1.2 × 20) = 3958 J/kg°C ≈ 4000 J/kg°C (2 sig. figs)”