Chemistry

The Heating Curve of Water

If water is heated under atmospheric pressure two kinds of physical changes can take place: the temperature can increase and the phase can change (from ice to liquid or from liquid to steam).

In this experiment, we will observe how these changes are related and use the data to graph and calculate the heat offusion and the heat of vaporization

As you may know from the study of specific heat capacity, the quantity of heat "q" required to achieve acertain temperature change is the product of three factors: the mass of the substance, its specific heat“C” (the specific heat of water is 4.18kJ/kgC° in SI uni ts or 1.00 cal/gC° in non-SI uni ts.) and thenumber of degrees the temperature changed, so q = m CΔt.

Materials:

1 - 250 mL beaker

Ice

Heat Source

Celsius Thermometer

Procedure:

  1. Mass the empty 250ml beaker and record the value in grams.
  2. Fill the beaker to the top with ice and mass both the beaker and the ice and record the value in grams.
  3. Subtract the mass of the empty beaker from the mass of the beaker and ice to obtain the mass of the ice and record the value in grams.
  4. Place the thermometer in the beaker of ice and record the temperature of the ice to the nearest tenth of a degree. NOTE: wait for the thermometer to settle before recording the temperature.
  5. Place the beaker of ice over a heat source and continually stir the ice using your thermometer. NOTE: Do not allow the thermometer to touch the bottom of the beaker.
  6. Every minute record the thermometers temperature and make a visual observation of the beaker.
  7. Continue to record the temperature of the contents of the beaker until the thermometer reads 105 degrees Celsius. Record all observations.
  8. Clean and return all equipment to the main lab station.
  9. Using your data construct a graph

Data:

  1. Mass of empty beaker = ______
  2. Mass of beaker and ice = ______
  3. Mass of ice = ______
  4. Initial temperature = ______

Time in Minutes / Temperature in degrees Celsius / Observations
0

Calculations:

  1. Graph a temperature time graph of your data so that temperature is your dependent variable and time is your independent variable.
  2. Calculate the amount of heat required to change the ice to steam. Below is the heating curve of water. Use the information in the chart to graph your data and calculate the heat.

TIME IN MINUTES

Part A: q = t x m x Cp ice

Part B: q = molwater x Hfus water

Part C: q = t x m x Cp water

Part D: q = molwater x Hvap water

Part E: q = t x m x Cp gas wter

qtotal = A + B + C + D + E