| My son Jack and I took some time out from playing | | | | than the water below, hot water rises. This would |
| with the educational toys he received for Christmas | | | | create a larger temperature difference with the air and |
| and went to a hockey game over the holidays. Like | | | | cool the water faster. Third, the warm water would |
| most 7 year olds, his favorite part is when the | | | | initially melt the ice on the ground, forming a better |
| Zamboni comes out to clean the ice. We had seen this | | | | bond that would cool the water faster. This also |
| a thousand times so I was stymied when Jack said, | | | | prevents layers of ice from chipping away. |
| "Why is there smoke coming out of the back?" It's | | | | So we filled up a jug with hot tap water and a second |
| steam I told Jack, they use hot water because it | | | | jug with cold water. We took 2 plastic cups and a |
| freezes faster. I could see the wheels turning now and | | | | short 2x4 outside. We filled each cup half full, the red |
| knew I was getting in over my head. "But ice is cold, | | | | one with hot water and the blue one with cold water |
| shouldn't they use cold water, Dad". Well, there was | | | | and set them on the walk. Then we found a patch of |
| only one period to go and a thousand questions, most | | | | ice on the driveway, laid the 2x4 in the center, and |
| of which I didn't have the answers to, so I told Jack | | | | poured hot water on one side and cold water on the |
| that when we got home we would do our own | | | | other side. It was 18 F so we went in to warm up. |
| science experiment to see whether hot or cold water | | | | We came back out an hour later. The 2 cups were |
| froze faster. | | | | mostly water. The red one had some ice above the |
| To get the most out of this I thought we should treat it | | | | water line and the blue one had some ice on the outer |
| as a science project. I looked through some of the | | | | edge of the water surface. |
| science toys Jack had and found a science kit that | | | | On the driveway, both sides of the 2x4 had turned to |
| showed how to do some experiments. Jack and I | | | | ice. When we touched the ice we could see our |
| made a plan and a list of all the things we'd need. We | | | | fingerprint on the cold water side. The hot water side |
| also searched the internet to see if there were any | | | | was frozen solid. |
| educational toys that might help us. We didn't find any | | | | We weren't sure what we just proved but we rushed |
| educational toys, but we did find some very interesting | | | | back inside, wrote down our observations, drew a few |
| facts. | | | | pictures and had some hot chocolate before bedtime. I |
| It turns out there are at least 3 physical processes that | | | | knew Jack was going to be excited when he |
| would explain why hot water freezes faster. First, hot | | | | explained his science experiment to his class on |
| water contains less dissolved air, this is why fish can | | | | Monday. |
| die in very warm water, a lack of oxygen. Liquids | | | | So next time you see that steam rising behind the |
| conduct heat much better than gas so hot water | | | | Zamboni you'll know why. As for my backyard ice rink, |
| would cool much more rapidly. Secondly, in a pool of | | | | if I can only wrap the garden hose around the |
| warm water, the water at the surface would be hotter | | | | barbeque. |