Thermal Pollution
Done By: Yuan Xin
3S433
Activity
It is to lower the temperature of water as much as possible without adding anything
to the water or decrease the volume of water.
Hypothesis: The greater the difference of the temperature of the surroundings and
the water, the greater the rate of heat energy lost from the water.
Apparatus needed:
1) A container made of copper
2) Laboratory Thermometer
3) Stop watch
4) Retort stand
5) 500ml of water at 80oC
Procedure of the experiment:
1) Place the thermometer tightly secured onto the retort stand, into the container,
however making sure that the thermometer do not touch the bottom of the
container (suspended in liquid)
2) Then, measure out the 500ml of water at 80oC and pour it into the container.
Make sure that the whole of the bulb of the thermometer is submerged into the
water for proper measurement to take place.
3) After all the water has been poured into the container, make a note of the initial
temperature of the water. Then, start timing using the stopwatch, whole reading the
reading on the thermometer every 15 seconds, up to a time of 5 minutes (20
readings)
4) Plot the data acquired into a graph with proper labeling of the x-axis being the
time taken (up to a maximum of 5 minutes) and the y-axis being the temperature of
the water
4) Repeat the steps above again 2 more times (triplicates).
Explanation for the setup:
1) I chose a container made of copper because copper is a good conductor of heat
energy and emits radiant heat energy from the water well to cool the hot water
within. Copper is one of the best conductors of thermal energy, but it is not the best.
Silver is a better thermal energy conductor, but silver is expensive and rare. Thus I
chose copper, which is cheap and easily available.
2) The container has a large surface area to maximise heat energy loss by the water.
3) The thermometer is used to measure the temperature of the water in the copper
container at regular 15s intervals up to a maximum of 5 minutes so as to record the
temperature change over the time period. To be more specific, the thermometer is needed
to measure the temperature of the water for the rate of temperature decrease of the water
and room temperature (temperature-initial minus temperature-final) and the temperature
of the surroundings (room temperature).
3) The stop watch ensures that the total time taken will be exactly 5 minutes for the water
to cool to find its rate of temperature decrease to the surroundings, and to help in providing
the 15 second readings
4) The retort stand secures the thermometer and prevents it from dropping (avoid breaking
of thermometer)
5) The experiment is conducted 3 times so as to obtain the average result to ensure that the
experiment is reliable and fair, as human error could happen and we do not want that.
Measuring changes in temperature of the water over the time period:
1) The temperature of the water at every 10s is recorded down.
2) This data is then plotted into a graph on paper with the x-axis being the time
taken and the y-axis being the temperature of the water so that we can see the
cooling curve of the water from 80oC to the final temperature.
Limitations of the experiment:
1) When pouring the water into the container, our timings have not started yet, and
the water, during the process of pouring would already lose heat energy to the
surroundings.
2) After all the water has been poured in, there is always a lag time to start the
timings going. (human error)
4) Copper, as said before, is not the best conductor of thermal energy, as compared
to silver, and results tabulated might not be as good as when using a silver container.
5) The setup is not a closed and isolated system and there will be heat loss to the
surroundings throughout the experiment.
Improvements that can be made to enhance the effectiveness of the experiment:
1) Use a data logger (connected to the computer with the other end in the water) to
obtain more accurate results and tabulated the results in a graph in the computer, as
usually such data loggers give accurate measurements and contribute to the
effectiveness of the experiment.
2) If possible, place the setups in a cold room (an air conditioned room could suffice)
so as to increase the temperature gradient between the hot water and the cooler
surroundings to facilitate a higher rate of heat transfer from the cooler surroundings
to the hot water.
Conclusion:
My hypothesis is correct. The greater the temperature gradient (difference in
temperature) of the surroundings and the water, the higher the rate of thermal
energy loss by the water (in this case, the surroundings has lower temperature than
the water, thus water loses thermal energy).