Presentation on theme: "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 "— Presentation transcript:
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
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 Results You 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 water Number of layers of paper towel Time of cooling How did you control this variable? Filled tubes to the same level / left same gap at top of tube Used the same number of paper towels on each tube We 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 valid Other variables could affect our data Was there a variable you could not control? What was it? Temperature of the room Air 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 bubble thin 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 MaterialDistance the bubble moved (cm) Test 1Test 2Test 3average w x y z91099 What would be the best way to display this data on a graph? line graphbar graphpie chartscatter 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 MaterialDistance the bubble moved (cm) Test 1Test 2Test 3average w x y z91099
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 material Mass (g) Change (mass evaporated) beforesoakingdrip dry W X Y Z
Scientists used both set of data to make a recommendation. They decided that material Y was the most suitable. Explain why? CHSB Section B material Mass (g) Change (mass evaporated) beforesoakingdrip dry W X Y Z MaterialDistance the bubble moved (cm) Test 1Test 2Test 3average w x y z91099
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 material Humidity 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.