Chem Class- September 30, 2009

Mr. Doktor checked our homework from last class today. He then went over a powerpoint on the Classification of Matter.

Here's a diagram I got from a Chemistry book on classifying matter:

As you can see, there are two types of pure substances: Homogenous and Heterogeneous.
Homogenous substances consist of only one visible component (Eg: distilled water, oxygen, graphite) and Heterogeneous substances contain more than one visible compent (Eg: chocolate chip cookie, granite).

You can also see in the above diagram that there are also two types of pure substances: Elements and Compounds.
Elements are substances that cannot be broken down into simpler substances by chemical reactions (Eg: oxygen, iron and magnesium)
Compounds are substances that are made up of two or more elements and can be changed into elements (or other compounds) by chemical reactions (Eg: water, sugar).
The differences between them are only visible at the atomic level

We also learned about Solutions.
A solution is a homogeneous mixture of 2 or more substances. The component present in the greater amount is the solvent and the component present in the smaller amount is the solute. The symbol (aq) is used when something is dissolved in water.

Finally, Mixtures:
Many mixtures are easy to identify, but others are easily confused as pure substances.
In Heterogenous mixtures the different parts are clearly visible (granite, sand, fog) and in Homogeneous mixtures the different parts are not visible (salt, water, air).
There are different methods to separate methods depending on the type of mixture. These include:

• By hand (Heterogeneous mixtures only)
• Filtration (Heterogeneous mixtures only)
• Distillation
• Crystalization
• Chromatography

The above are all physical changes.