Physics_10grade_Unit10.3.1.1 - Lab Work Handout 33

Laboratory equipment (experimental procedure may need adjustments depending on each school’s equipment)

·         DC power supply (12 V) and cables

·         Two Pasco GLX data loggers and two current/voltage sensors (or two multimeters, if Pasco equipment is not available)

·         Phywe heating coil (immersion heater)

·         Beaker

·         Stopwatch

·         Calorimeter with lid and stirrer

·         Pasco GLX data logger with temperature sensor (or a thermometer, if Pasco equipment is not available)

Health and safety

Electric shock hazard. Proceed with extreme caution when using electric devices.

Do not touch any metal part of the wires or other equipment with your hands.

Proceed with caution when dealing with hot water, as it may cause severe burns on your skin.

Do NOT spill water on any component of the circuit and keep a clean and safe desk.

Call your teacher to verify the circuit BEFORE turning the power supply on.

Experimental Procedure

1. Build the electric circuit shown in Fig. 1, using the laboratory equipment that has been given to you.

Set the potential difference in the power supply to about 12 V.

In Fig. 1, R is an immersion heater. Do NOT turn the power supply on yet.

2. Fill the calorimeter with about 200 mL of water, and put the heating coil inside it. Place the lid with heating coil, thermometer and agitator rod onto the calorimeter (Fig. 2). Record the temperature for t = 0 s on the table below.

3. Call your teacher to verify the circuit.

After your teacher’s approval, turn on the power supply and start the stop watch simultaneously.

Record the value of the potential difference V across the heater and the current I through it.

     V = ………………………….. V                               I = ………………………….. A

4. Record the water temperature 1 min intervals, for about ten minutes. Stir at regular intervals; and record the measured values on the table.

5. Turn off the power supply at the end of the experiment.

Questions

1.  Calculate the power of the heating coil.

P = …………………..………………..W

2. Calculate the value of the energy E delivered by the heating coil for every time t. Record your results on the table.

On the space below, as an example, show how you calculated the energy for time t = 4 min.

E = …………………..………………..J

3. Use your results to plot a graph of T on the y-axis against E on the x-axis.

Plot this graph on the grid of the next page.

4. By referring to your graph, suggest a relationship between energy and temperature.

……………………………………………………………………………………………………………………………………………………………………………………………….………

……………………………………………………………………………………………………………………………………………………………………….……………………..……….

5. The heating coil releases heat, which is absorbed by water. What do you think is happening at a molecular scale? What happens to this energy and how does it relate with temperature?

Make your own suggestion! There are no “wrong” answers to this question at this stage.

……………………………………………………………………………………………………………………………………………………………………………………………….………

……………………………………………………………………………………………………………………………………………………………………….……………………..……….

……………………………………………………………………………………………………………………………………………………………………………………………….………

For teacher only

For the first lesson of the unit, an introductory simple experiment is suggested to engage the students in the topic and, also, to allow them to conclude that temperature is directly proportional to energy, a concept that will be explained later and generalized for an ideal gas.

As year 10 students, some problems may be expected when building the circuit, specifically connecting the ammeter and voltmeter.

Students will observe that the water’s temperature increases as more energy is delivered to it.

It is expected that students conclude that temperature and energy are directly proportional (question 4).

At this stage, it is not expected that students understand the energy supplied by the heating coil is absorbed as kinetic energy by water molecules. Different types of answers are expected. Although, the teacher should be aware that question 5 is a mere starting point for a discussion on one of the following lessons and, as so, at this stage, there are not “right” or “wrong” answers to this question.