INTRODUCTORY PRACTICAL ACTIVITY
ON THERMODYNAMICS
NAME: ......
1.Using the Thermistor
Aim: To use a temperature measuring device other than a thermometer
Equipment: Thermistor, wires, multimeter
Put the multimeter on the Resistance (Ohm) scale. Record the meter reading on the top scale.
......
Now put the thermistor between your fingers, note what happens on the meter and read the reading after a few minutes......
What happens to the resistance of the thermistor as its temperature rises?
......
......
2.Methylated Spirits and Cotton Wool
Dab your wrist with the "metho". What do you experience? Why?
......
......
3.Electric Fan
Record the reading on the thermometer, then dip it in the water and place it in front of the fan and read the temperature again.
Initial Temperature :......
Temperature after wetting::......
Why do you think the temperature changed? ......
......
4.Thermal Conductivity
Aim: To see how different metals transfer thermal energy
Equipment: Star of four metals with solid wax on each end sitting on a tripod on the side bench, a bunsen burner and a stop watch
Method: Select a mat on which the wax at the end of the metal strips is solid. Some may have melted wax, in which case the tripod and the metal strips will still be hot. Place the metals centrally on the tripod over the bunsen. Light the bunsen and start the stop watch.
Record the time at which each of the waxes begins to melt
A: Aluminium: ...... B: Brass :......
C: Copper :...... I: Iron :......
Which metal transfers thermal energy the fastest?
......
At the end of the exercise use the mat to return the equipment to the side bench to cool.
5.Bimetallic Strip
Equipment: Bimetallic strip and a bunsen burner
Bimetallic strips are two lengths of different metals riveted together with an insulated handle.
Heat the strip evenly along the edge and describe what happens.
......
Give an explanation of what you see.
......
......
6.Newton's Law of Cooling
Aim: To investigate how hot objects cool down
Equipment: A hot plate, beakers of water, temperature probes, datalogger
The water has been heated to a high temperature and allowed to cool down. The datalogger is displaying the temperature against time.
Describe the shape of the graph……………………………………………………
Where you have seen a similar graph......
7.Transferring Energy Quickly
The hollow copper tube is very effective in transferring energy quickly from one end to the other.
Equipment: copper tube, copper, brass and steel rods
Hold the copper tube by the end that has a short tube attached and put the other end in the flame. Put an end of each of the metal rods in the flame. You will need both hands of both partners for the tube and the three rods.
Note how quickly the energy the energy is transferred in the copper tube.
There are many other things to observe with the copper tube.
What else did you notice?
......
......
Can you explain why the copper tube is so fast? What do you think is inside the tube?
......
......
8.As Cold as Ice!
Hold a small block of ice in your initially dry hand and allow the ice to melt. Take note of how cold the water produced feels compared to the unmelted ice.
Does melted water feel colder than the ice or does it feel just as cold as the ice?
……………………………………………………………………………………………………
9.Can you be a Thermometer?
Place your left hand in the bowl of hot water and your right hand in the bowl of very cold, icy water. Leave your hands in the water while your partner uses a thermometer to measure the temperature of the water in each bowl.
Temp of hot water = …………………Temp of cold water = ………………………..
After about two minutes place both hands in a the middle bowl of lukewarm water.
Describe briefly what each hand felt when placed in the lukewarm water
Left hand: …………………….………………………………………………………………
Right hand: ……………………………………………………………………………………
Suggest an explanation ofr your experiences
…………………………………………………………………………………………….…..
……………………………………………………………………………………… ………..
10.Radiometer
You will be investigating infra-red radiation coming from a hot source. A radiometer is a set of vanes inside an evacuated glass container. There is very little air to slow down the vanes. One side of each vane is painted black, the other is shiny.
Place the radiometer in front of the infra-red source.
Which way do the vanes move? Does the shiny side go towards the source or away from the source? ………………………………………………………………………………………….
Try putting different materials between the radiometer and the source to see if any of the materials are transparent to infra red radiation.
Which materials (if any) were transprent to infra-red radiation? ………………………………..
11.Converting Thermal Energy into Electricity
The device uses a semiconductor to convert the energy in the difference in temperature into electrical energy to drive the fan.
Observe the two temperatures and the speed of the fan for a few minutes and comment on how they are related.
…………………………………………………………………………………………………..
…………………………………………………………………………………………………..
The device also can run in reverse, that is, place it in two liquids at the same temperature, connect a low voltage DC source, and one liquid will cool, while the other heats up.
Suggest a use for this device in either mode of operation: ………………………………………
H & C/May ‘93/DOK