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  • We also talked about Chemistry not only being the study of matter, but the changes that

  • matter undergoes.

  • We're going to say that this is broken down into two types of category.

  • We're going to have our physical changes and our chemical changes.

  • Now, in the first blank, we have their changes in the form of the substance, but not its

  • chemical composition.

  • Basically, we're going to say that these are physical changes.

  • What do I mean by not a change in its chemical composition?

  • For example, I have icewhich is solid water and then I just leave it out and it melts.

  • It goes from solid water to liquid water.

  • At the end of the reaction, it's still water.

  • It began as water.

  • It's still water at the end.

  • I didn't change its chemical makeup.

  • Once I change its chemical makeup or chemical composition, it should stop being water.

  • It should change into something entirely different.

  • Now the second type of change creates new substances with different properties and different

  • chemical compositions, so we say that this is chemical.

  • For example, I have that liquid water and I super heat it.

  • That little triangle means heat, so I super heat the water, that ice, heat it so much

  • so, then now it becomes H2 gas and O2 gas.

  • It becomes hydrogen gas and oxygen gas.

  • It started off as water, but now it's no longer water.

  • It's hydrogen gas and oxygen gas which are very different from water.

  • As a result, because they're so different from water, they're going to have different

  • properties, different melting points, different boiling points, different densities.

  • That's what we mean by a chemical change.

We also talked about Chemistry not only being the study of matter, but the changes that

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