Keeping Cool ISA

In this ISA you are going to investigate the effect that the evaporation of sweat has on the cooling of a body.

CHSB

CHSB Instructions for the practical

Thermometers

Boiling tube wrapped in a paper towel

1. Set up two boiling tubes with a paper towel wrapped around the outside of both. Secure the towel with an elastic band.

2. From a beaker of hot water, add the same amount of water into both boiling tubes. Leave a 2cm gap at the top.3. Carefully insert a thermometer into each tube. Leave for 30 seconds.

4. Using a pipette, take some hot water from the beaker and wet the paper towel on boiling tube .

5. Record the starting temperatures. Leave for 12 minutes and record the final temperatures of both boiling tubes.

Paper towel

CHSB Understanding the practical

This experiment models the cooling effect created when we sweat.

What does the paper towel represent in the model?

What does the hot water in the tubes represent?

What does the hot water added to the outside of tube represent?

Thermometers

Boiling tube wrapped in a paper towel

Recording ResultsYou need to draw up a results table before you begin the practical to record your data.

CHSB

Your table will need: a column for the tube number, another for the starting temperature, one for the end temperature and one for the fall in temperature. Put the units in each column heading as needed.

Section A

What was the dependent variable in your experiment and what measuring instrument did you use to measure this variable with?

CHSB

Temperature of the water and a thermometer.

What variables did you control in this experiment?

Volume of waterNumber of layers of paper towelTime of cooling

How did you control this variable?

Filled tubes to the same level / left same gap at top of tubeUsed the same number of paper towels on each tubeWe timed both to 12 minutes using a stop watch

Section A

Why was it necessary to control this variable?

CHSB

Otherwise the results / conclusion would not be validOther variables could affect our data

Was there a variable you could not control? What was it?Temperature of the roomAir currents in the room

What does reliability mean when talking about your data?

When the experiment is repeated you get the same results.

Are your results reliable or not?Yes, because other groups got the same pattern of results that we did.No, there was no pattern to our results / other groups got different result / we had anomalies in our data

From your data and graph, what conclusions can you make about this experiment.

The wet boiling tube cooled down faster that the dry one.

Being wet does not affect the cooling rate when the whole duration of the experiment is taken into account.

Explain how your data / graph supports your conclusion.

Eg the temperature fall for the wet tube was 18 Celsius but in the same time the dry tube temperature only fell by 9 Celsius.

CHSB Section A

A manufacturer wishes to investigate how quickly different materials soak up and evaporate water so they can be used in sports clothing.

Investigating evaporation from different materials

CHSB Section B

Look carefully at the apparatus they used and work out how they used it. You need to be able to say, step by step how the experiment worked.

Investigating evaporation from different materials

CHSB Section B

ruler

water reservoir

bubblethin glass tubing

test material

evaporation

Explain how they might use this apparatus to see which material soaked up and evaporated water most quickly. Steps must be in order.

Investigating evaporation from different materials

CHSB Section B

1. Fill the apparatus with water

2. Put the material in position

3. Record the position of the bubble

4. Measure how far the bubble moves in set time

5. Repeat with the same / different material

6. Make sure that the pieces of material are the same size / thickness

Here are some of the results that the scientists obtained from doing this experiment

CHSB Section B

Material Distance the bubble moved (cm)Test 1 Test 2 Test 3 average

w 10 12 11 11x 18 17 19 17y 15 15 16 15z 9 10 9 9

What would be the best way to display this data on a graph?

line graph bar graph pie chart scatter gram

Based on the data only, which material should be recommended for use by the scientists

Investigating evaporation from different materials

CHSB Section B

Material X.Explain why.

This material soaked up / evaporated the most water

Material Distance the bubble moved (cm)

Test 1 Test 2 Test 3 average

w 10 12 11 11

x 18 17 19 18

y 15 15 16 15

z 9 10 9 9

Did you get any anomalous results in your experiment?

CHSB Section B

No. The results fit the pattern I expected

Yes. The results were a lot different to the pattern

Repeat the test / trial that gave the anomalous data.How should anomalous data be dealt with.

Scientists decided to do another test. The soak test.

They took equal size bits of the 4 different materials and weighed them.

Then they soaked them and weighed them

Then they hung them up to drip dry for 20 minutes and weighed them again.

CHSB Section B

How can you tell that there is a problem with the data?

CHSB Section B

Mass when dry is smaller than the mass when drip dried for material W

materialMass (g)

Change (mass evaporated)before soaking drip dry

W 20 25 17 8X 15 24 17 7Y 18 33 23 10Z 22 40 36 4

Scientists used both set of data to make a recommendation. They decided that material Y was the most suitable. Explain why?

CHSB Section B

materialMass (g)

Change (mass evaporated)before soaking drip dry

W 20 25 17 8

X 15 24 17 7

Y 18 33 23 10

Z 22 40 36 4

Material Distance the bubble moved (cm)

Test 1 Test 2 Test 3 average

w 10 12 11 11

x 18 17 19 17

y 15 15 16 15

z 9 10 9 9

CHSB Section B

Y lost the most water in the soak test (test 2) and was a close second in test 1.

X was best in the first test but came third in the second test.

Could there be a reason why they would not recommend material Y

The material may be too expensive.It might not look good.Not enough research / test have been carried out to make a firm recommendation

CHSB Section B

What variable should have been controlled in test 2 (soak test) so that valid data was obtained.

Room temperature.Size of materialHumidity in the room

How could more precise mass data be obtained in experiment 2?

Use a balance that can measure to more decimal places than the one they used.

What could you do to make your data more precise?

Use a thermometer with finer (smaller) scale divisions.