Question 151
Feeling the effects of evaporation. You need water, liquid soap, ethanol or isopropanol (isopropyl/rubbing alcohol), a dropper pipette, paper towels and access to hand-washing facilities or running water.
Safety: no other liquids should be used except ones intended for use directly on the skin.
1 Put one drop of water on the back of your hand using the pipette.
2 Spread the drop thinly with a finger from the other hand.
3 Gently blow on the wet skin.
4 Remember how this feels.
5 Dry the hand with a paper towel.
6 Repeat steps 1–4 with liquid soap, then wash it off with plenty of water before drying.
7 Repeat steps 1–4 with ethanol or isopropanol; wash your hand to remove it before drying.
Explain why it would be difficult to present the results of this activity in a bar chart.
Safety: no other liquids should be used except ones intended for use directly on the skin.
1 Put one drop of water on the back of your hand using the pipette.
2 Spread the drop thinly with a finger from the other hand.
3 Gently blow on the wet skin.
4 Remember how this feels.
5 Dry the hand with a paper towel.
6 Repeat steps 1–4 with liquid soap, then wash it off with plenty of water before drying.
7 Repeat steps 1–4 with ethanol or isopropanol; wash your hand to remove it before drying.
Explain why it would be difficult to present the results of this activity in a bar chart.
