Lab: Enthalpy
In this lab, we will investigate the concept of enthalpy, which is a measure of the heat content of a system. Enthalpy is represented by the symbol H and is defined as the sum of the internal energy of a system plus the product of the pressure and volume of the system.
Materials:
- Styrofoam cup
- Thermometer
- Water
- Hot plate or burner
- Stopwatch
Procedure:
1. Fill the Styrofoam cup with a known quantity of water.
2. Measure and record the initial temperature of the water using the thermometer.
3. Heat the water using the hot plate or burner until it reaches a boiling point.
4. Once the water reaches boiling point, immediately remove the heat source and start the stopwatch.
5. Stir the water and continue to monitor the temperature.
6. Record the highest temperature reached by the water after boiling.
7. Calculate the change in temperature of the water (final temperature - initial temperature).
8. Calculate the enthalpy change of the water using the formula:
\[ \Delta H = mc\Delta T \]
where:
ΔH = enthalpy change
m = mass of water (g)
c = specific heat capacity of water (4.18 J/g°C)
ΔT = change in temperature (°C)
9. Compare the calculated enthalpy change with the known enthalpy of vaporization of water (2260 J/g).
10. Dispose of the water properly.
Conclusion:
In this lab, we investigated the concept of enthalpy by measuring the change in temperature of water as it went through a phase change from liquid to vapor. By calculating the enthalpy change using the formula provided, we were able to determine the heat absorbed by the water during this phase change. This lab demonstrates the importance of enthalpy in understanding the heat content of a system.