In the experiment on the polar ice caps melting I found that when my ice cubes melted, there was a little overflowing of the cup (but not a lot). After thinking about it a little I believe that this is due to the density of the ice versus that of the water. Since ice is less dense than water it floats, this means it has less mass/unit of volume. When ice melts it takes up a little less room than it did before the phase change. This can be demonstrated by putting a soda into the freezer and letting it freeze. The results are: the can deforms, explodes, and I get to clean the freezer (or as clean as my wife makes me)!
We can think of the question of sea level rising due to global warming as a example of this. There will be a little sea level rise from the glaciers that are already in the water. It is important to note though that the effect of global warming is not just melting ice in the form of glaciers but also ice that is on the continents. Because of this, the experiment can be considered to be understating the effect of melting the polar ice caps.
This experiment paves the way for a whole bunch of questions that will have to be "cleaned up" before the end of the segment. Students should know what causes global warming, what scientists think the effect will be, what levels they are predicted to raise to, and what other effects will global warming have on the environment. Tied to these concepts is the question "What can we do about this and how do we stop it?" It is easy to get the students involved in the topic of global warming, the issue is trying to imact them enough to help do something about it.
David,
ReplyDeleteI started to think about density of the ice, as well. Immediately, my mind shifted to last year when we had a snowstorm here in Georgia and other parts of the country. I remembered the effect of the melting ice and snow. It produced mass flooding in some areas. By the same token, you are correct in your statement about the experiment understating the effects of the melting polar caps. It, also, consists of sea ice and ice on the continents. Your question makes a good point. We know we have a problem, we need to do fix it, we need to slow down the process, and we need to stop it. However, as you mentioned the concern now lies in getting students to see the urgency and to get involved in finding a solution. It really is a matter of changing our habits, reducing pollution, seeking alternative types of fuel, and weaning ourselves off fossil fuels. Unfortunately, it seems easier said than done.