| Category | Activities |
| Badge | Scientist |
| Time to allocate (mins) | 15 |
| Outcome | The relative temperature… is it warmer or colder than when you last checked? Look at the level of the water inside the straw. It will rise as the air gets warmer, and lower when the air cools. |
| Resources | Clear plastic bottle Rubbing alcohol Food colouring Water Straw Clay/plastecine |
| Instructions | How to make one: Take a clear plastic or glass bottle. Fill it 1/4 of the way with
rubbing alcohol. Then add water till the bottle is half full. (Note: you
could use just water, but it responds more slowly than with the
alcohol.) Add food coloring or liquid watercolor so it’s easier to see
the water level. Place a clear straw in the bottle so that it is
suspended where the bottom end is in the liquid, but not
touching the bottom of the bottle and the top end is poking out the top
of the bottle. (In the picture, the straw just barely reaches the top of
the bottle – it’s fine if yours sticks out a little or a lot.) Now
anchor the straw in place with clay (we used Model Magic, but play-dough
or silly putty would work). Do not seal the top end of the straw – it
needs to be open to the air in order to work. (When the water and air in
the bottle heat up, they expand, but can’t escape the bottle, so the
water is pushed up the straw.)
To use: Test it – what level is the water in the straw at? Place it somewhere cooler – like in the refrigerator. What happens to the water level? Now take it back out to room temperature. How does the water level change? |