Classification of Matter - September 30 Class

In this class, we learned about Homogeneous and Heterogeneous substances.. We distinguished that tap water is a heterogeneous substance because there are other chemicals that are put into the tap water when running through the drains, sinks, etc. Mr. Doktor also passed around a beaker filled with aluminum pieces and salt, a heterogeneous mixture that didn't react together. We also learned that there are certain ways of separating mixtures, which are mostly physical changes.

Notes:
Classification of Matter

• Understanding matter begins with how we name it. We can divide matter into two parts: Homogeneous substances and heterogeneous substances
  
• Homogeneous: consists of only one visible component
  - distilled water, oxygen, graphite
  
  
  
• Heterogeneous: contain more than one visible component
  - chocolate chip cookie, granite

Pure Substances:

• There are 2 types of Pure Substances:
  Element: substances that cannot be broken down into simple substances by chemical reactions
  - oxygen, iron, magnesium
• Compound: substances thar are made up of 2 or more elements & can change into elements (or other compounds by chemical reactions)
  - water, sugar

Telling the difference

• It is often very difficult to know if something is an element or a compound
  - The differences are only "visible" on the atomic level
• One method is to connect the substance to an electric current. This technique. called electrolysis can split the compound apart into its constituent compounds

Solution

• A solution is a homogeneous mixture of 2 or more substances
  - Solutions usually involve but don't have to (fog, steel)
• The compound present in greater mount is the solvent
  - Water is the most ommon solvent
  - The symbol (aq) is used when something is dissolved in water
• The compound present in smaller amount is the solute
  - In salt water, salt is the solvent

Mixtures

• Many mixtures are easy to identify (chocolate chip cookies) but others are easily confused as pure substances
• In heterogeneous mixtures.. the different parts are clearly visible (granite, sand)
• In homogenous mixtures.. the different parts are NOT visible (salt, water, air, brass)

Separating Mixtures

• There are many methods to separate mixtures, depending on how the type of mixture
  - By Hand (Heterogenous mixture only)
  - Filtration (Heterogeneous mixture only)
  - Distillation
  - Crystallization
  - Chromatography
• All of these are physical changes