Physics
Lab 2.6 Heat Capacity & Latent Heat
Overview
In this laboratory class we use a small immersion heater
to heat a known quantity of water in an insulated
container and plot the increase in temperature of the
water with time. The immersion heater should provide a
constant supply of energy at the element’s Wattage
rating. From this we can calculate the specific heat
capacity of water.
We also use the immersion
heater to boil the known quantity of water for a fixed
period of time. We can determine the latent heat of
vaporization of water from the amount of water left in
the container after the boiling process has been
completed.
Experiment
2.6.1 Heat Capacity of Water
Equipment
Small immersion heater or electric kettle
Insulated container – flask or foam cup.
Thermometer
Stopwatch
Measuring cylinder
Procedure:
- Place a measured
amount (200 cm3 or 300 cm3
) of water in the insulated container.
- Note the power
consumption rating of the immersion heater. (e.g.
200 Watts)
- Place the immersion
heater in the water
- Before connecting the
immersion heater to the power outlet, measure the
temperature of the water.
- Connect the heater to
a power outlet and start the stopwatch.
- Measure and record
the temperature of the water at regular intervals
until it starts to boil.
- Note the time at
which the water starts to boil.
- Allow the water to
boil for a fixed period of time.
- Unplug the heater at
the end of this period.
- Transfer the
remaining water to a container that is not
insulated and allow it to cool to below 40ºC.
- Measure the volume of
the water.
Calculations
Calculate the specific
heat capacity of water as follows:
- Plot the increase in
temperature of the water with time.
- The middle portion of
the graph should be a straight line (roughly)
- From the slope of
this line, estimate the rate at which the water
was increasing in temperature.
- From this, calculate
the number of seconds per ºC.
- Calculate the number
of Joules provided by the heater during this time
from the heater’s Wattage.
- Divide this by the
mass of water used. (assume a density of 1 g / cm3)
- Calculate the
specific heat of vaporization of water as follows:
- Determine the amount
of water that evaporated during boiling from the
difference in volume. (Assume a density of water
of 1 g / cm3) Convert the mass of
water that evaporated to kilograms.
- From the heater’s
rating, determine the number of Joules of energy
supplied to the water during the time that the
water was boiling.
- Divide the number of
Joules by the number of kilograms of water that
evaporated.
- This gives the latent
heat of vaporization of water.
Results
– Experiment 2.6.1
Specific
Heat Capacity of Water
Volume of water used cm3
.................................................................................
Immersion Heater Rating
Watts
..........................................................................
Time
(minutes)
|
Temperature
(ºC)
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Specific
heat capacity of water =
....................................................................
Latent Heat of
Vaporization of Water
Immersion Heater Rating
Watts
| Volume of water at start of
boiling |
|
| Volume of water after boiling |
|
| Volume of vapor formed = |
|
| Time that water was boiled |
|
| Energy provided during this time
= |
|
| Latent Heat of Vaporization = |
|
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