Wednesday, July 29, 2009

Chemistry Journal

Research question: What is the difference of a chemical change and a physical change?

First, i will tell you what is a chemical change and the factors that shows that is is a chemical change.
A chemical change is a change in matter that occurs on the molecular level. Mostly, this change is irreversible, meaning you can’t go back after the change has been done. Say you have a nail made of iron. Now you cut that piece in half. Is it still iron?
Take an identical nail made of iron and throw it into a blazing hot campfire. Assume that the campfire is so hot that the iron begins to melt. Is it still iron?
Again, take another nail made of iron and let it sit outside and rust. Is it still iron?
In the example with the iron nail, the first two changes are physical changes, because the end product is still iron. You cut it in half, it is still iron. You melt it, even though it is shaped differently, it is still iron. However, if the iron rusts you can’t take rust and make it into iron again. Therefore, the rusting of iron is a chemical change. It also turns out that you can change rust back into iron, but it takes so much energy that it almost never happens. How can you tell whether a change is a chemical change? It is actually very easy here are the factors: Colour changes, whether the item releases or absorbs energy, odour changes and production of gases or solids.

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