Specific Heat Capacity Flashcards
Specific heat capacity (c) is:
The amount of energy required to raise the temperature of unit mass of a substance by 1 K without a change of state.
energy supplied =
∆Q = mc∆T
Assumptions made when doing specific heat calculations:
- No evaporation
- No heat loss to surroundings
- Heater is 100% efficient
For an inversion tube of length L:
Specific heat capacity = gLn/ΔT
where n is the number of inversions
Measuring the specific heat capacity of a metal.
- With a block of metal of a known mass
- Insert a heating component into the metal.
- Insert a thermoniter into a second hole to measure temperature rise.
- Use water or oil to improve thermal contact the metal and thermoniter.
- mcΔT = IVt
- c = IVT/mΔT
Measurement of the specific heat of a liquid
- Put a polystyrene jacket round metal calorimeter for insulation and a lid to prevent heat loss through the top of the calorimeter.
- Place a known mass of liquid (ml) in previously weighed copper calorimeter (mc).
- Electrically insulated heater (12 V) is placed in the liquid.
- Record initial temperature (T₁) of liquid using a thermometer and switch heater on.
- Record heater current I and heater pd V.
- Leave for large rise in temp but keep stirring to ensure an even temperature and switch heater off.
- Record final temp (T₂) after a final stir and time (t).
- ∆Q = ItV = (ml*cl + mc*cc)(T₂ – T₁)
For a solar panel energy supplied per second:
mcΔT/t
In showers and solar heating panels water is:
Heated as it passes through them continuously and the water is hotter at the outlet than the inlet.
A hot liquid or object at a specific temperature T₁ is transferred to a container already containing another liquid at a lower temperature T₂.
- The ‘mixture’ eventually reaches thermal equilibrium at a middle temperature T₃.
Heat given out by liquid
= mLcL(T₃ – T₂)
=
heat taken in by water + heat taken in by copper = mwcw(T₂ – T₁) + mccc(T₂ – T₁)
