January 26, 2011

Today in class we talked about hot air and cold air and their affect on solids and liquids. We started by going over our homework. First, we went over the problem with the food coloring and the water. Most of us observed that the coloring spread quicker through the hot water, at a medium speed in room temperature, and slowly in the cold water. But why is this? Well, with the hot water, the particles are moving very fast all around the container so there is more room between these speeding particles for the coloring to dissolve into. With the cold water, the particles were moving very slowly so there wasn't a lot of room for the coloring to dissolve into which is why the dye set in slower than the hot water.

Then, we went over the problem with the water bottles. For this question, we needed to put a water bottle in the freezer and leave one water bottle at room temperature and wait for a few hours. After 3 hours we would check the results. We noticed that the room temperature bottle kept its shape and stayed normal, but the freezer bottle was a different story. The freezer bottle seemed to colapse on itself. This happend because there were more air particles in the freezer outside the bottle than there were inside the bottle. These outside particles had a stronger force than the inside particles causing the water bottle to look like the picture on the right. (Freezer bottle on the left, room remperature on the right)

Lastly, we had the ball and ring experiment. If you held the ball and ring perpendicular to each other, trying to get the ball through the ring, it would not fit. So how could we make it fit? What finley did was he put the ring in boiling water and put the ball in ice water. This made the ring expand, and it made the ball contract causing the ball to fit in the ring perfectly.

(picture in the left is original ball and ring, at the right is the ball after soaking in cold water)

Overall, we took in a lot of information today in class. We learned about why food dye spread quicker in some temperatures than in others (the reason gave me a little trouble), and how to make things expand and contract. Finley connected the things we learned today to a real life example of why we need to know this. He used the example of the bridge supports being oddly shaped. This was important because the bridge's metal could expand in the summer days but then contract again at night. These supports help the bridge stay up all year long. It's just something to think about next time you go over a bridge.

KS