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PHYS - Measuring Specific Heat Capacity of Water

Physics, specific heat capacity, heat, energy - IBDP | DSE | GCE | IAL | AP Physics

· physics,heat transfer,energy transfer

The experimental setup to determine to specific heat capacity of water is like this 👉

- Pour a known mass of water into the calorimeter.
- Inside the calorimeter is a heating coil connected to the electric circuit. The outside material of the calorimeter is an insulating material so that heat loss is minimized.
- Mark down the temperature of the water before turning on the power supply.
- Turn on the power supply to a certain voltage.
- Mark down the readings on the ammeter and voltmeter.
- After a few minutes, turn off the power supply, and mark down the temperature at this point.

**Important concepts you need to know in this experiment:**

- Electrical energy is converted to heat energy by the heating coil.

- Formula for electrical energy:

**E = Pt = VIt**

E = electrical energy (J)

V = voltage (V)

I = electric current (A)

t = time (s)

- Formula for calculating amount of heat energy added:

**Q = mc∆T**

Q = heat energy (J)

m = mass (kg)

c = specific heat capacity (J/kg·°C)

∆T = change in temperature (°C)

Once you have obtained the voltage, current, and change in temperature, you need to plug these values into the equations.

- Calculate the electrical energy supplied by the system by using the equation E = VIt.
- Since electrical energy is converted into heat energy, the heat energy added to water is equal to the amount of electrical energy you just calculated.
- The specific heat capacity of water then can be calculated by using the equation: c = Q / (m∆T)

Repeat the whole experiment several times and find the average value for specific heat capacity.

**Differences between Experimental Value and Real Value**

The known value for the specific heat capacity of water is 4200 J/kg·°C. You may find that the value you obtained from your experiment is slightly different from the actual value.

What are some possible reasons for the difference?

- The electrical energy supplied is also used to heat up the heating coil.
- There may be some heat lost through the calorimeter casing to the surroundings.
- Experimental errors, such as when using the balance to calculate the mass of water or when using the temperature to read the temperature
- When you measured the temperature of water after heating up, the temperature may not have been constant for all regions of water. Therefore, it is important to stir the water before measuring the temperature to make sure the temperature is homogeneous.

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