Jc Aqa Gcse 230 P1a1 2 Pcttn Testing Surfaces

P1a 1.2 Practical sheet Teacher notes

Testing different surfaces Aims 1 To carry out fair tests to compare different surfaces in terms of emission and absorption of radiation. 2 To enable students to compare cooling due to radiation from different surfaces. 3 To enable students to compare absorption of radiation by different surfaces. 4 To provide students with practical experience of measuring temperature changes and using a stopwatch.

Teaching notes 1 In Part 1, the temperature of hot water in two beakers is measured every minute for at least ten minutes. One beaker should be wrapped in shiny metal foil and the other one in matt black paper. a)

b)

c)

Each group of students could be supplied with the two beakers and asked to compare heat transfer from them. The students could use a measuring cylinder to ensure there is the same volume of water in each beaker. The hot water could be supplied by the teacher using a kettle. The starting temperature does not need to be exactly the same for each beaker as comparisons can be made using the graph. However, low-attaining students will probably find the comparisons easier if the starting temperature is the same for each beaker. Each beaker should be fitted with a lid as heat loss due to evaporation of water from the beakers will affect the results. Also, each beaker should be on an insulating mat to reduce heat transfer through the base. Timing could continue for more than ten minutes according to how much time is available. Remind students to stir the water between measurements. Both sets of measurements should be plotted on the same graph. Students can compare the cooling rates either in terms of the time to cool from a certain temperature to a lower temperature or in terms of the temperature change from a certain temperature in a certain time.

2 In Part 2, the temperature of cold water in the same two beakers is measured every minute for at least ten minutes. a)

b)

Cold water could be provided from a bucket of cold water containing ice or from plastic bottles of tap water kept in a refrigerator until needed. The water temperature should be at least 10°C below room temperature at the start. The rate of change of temperature will probably be less than in Part 1 as the temperature difference at the start between the water and the air is less here. For this reason, it may be necessary to make measurements for more than ten minutes. Again, remind students to stir the water between measurements.

AQA Science © Nelson Thornes Ltd 2006

P1a 1.2

1

P1a 1.2 Practical sheet Continued … c)

Both sets of measurements should be plotted on the same graph. Students can compare the rate of gain of heat transfer either in terms of the time to warm up from a certain temperature to a higher temperature or in terms of the temperature change from a certain temperature in a certain time.

Teaching assistants 1 Low-attaining students will need assistance with the instructions in each part. They may also need to be shown how to use a stopwatch and how to measure the temperature each minute. Make sure they know not to leave the thermometer lying near the edge of the bench (or the measuring cylinder) and they do not reach over the equipment. Increase the size of the work sheets (and graph paper) to A3 if necessary. 2 Assist students to plot the measurements on graph paper if necessary.

Safety 1 Ensure students know not to clutter their working space for the practical work with other items. 2 Remind students not to leave thermometers and measuring cylinders near to the edge of the bench or table and not to reach over equipment. 3 Provide paper towels to mop up any spillage of water. 4 Take care with hot water.

AQA Science © Nelson Thornes Ltd 2006

P1a 1.2

2

P1a 1.2 Practical sheet Continued …

Technician notes Equipment For each student (or group): • Liquid-in-glass thermometer. • Two beakers of water (preferably plastic), lids and insulation mats, spare beaker. • Shiny metal foil, matt black paper, both cut to size to fit around the beakers. • Rubber bands or Sellotape to keep the material in place on the beaker. • Stopwatch. • Measuring cylinder with capacity to measure maximum volume of water in beaker. • Paper towels. • Graph paper for each student. For the whole class: • Kettle to be used by the teacher to supply hot water. • Cold water (either in plastic bottles kept in a refrigerator until needed or a bucket of ice-cold water).

Safety 1 Ensure students know not to clutter their working space for the practical work with other items. 2 Remind students not to leave thermometers and measuring cylinders near to the edge of the bench or table and not to reach over equipment. 3 Provide paper towels to mop up any spillage of water. 4 Take care with hot water.

AQA Science © Nelson Thornes Ltd 2006

P1a 1.2

3