Learning check
Once you have watched the video, check your learning with this quiz.
Elements and chemical compounds
An element consists of only type of atom.
Examples:
- Iron, Fe
- Sulfur, S
Iron filings consist only of iron atoms, Fe.
Sulfur powder consists only of sulfur atoms, S.
Mix them and you have nothing more than a mixture of iron and sulfur.
Mixture:
- Two or more substances/chemical compounds included.
- The substances can relatively easy be separated from each other.
- The substances maintain their original properties.
Example:
- Iron is still magnetic.
- Sulfur is still yellow.
In a mixture of iron and sulfur, the sulfur is still yellow …
… and the iron is still magnetic.
Chemical compound
- Characteristics differ from original elements
If you heat the mixture of iron and sulfur, it reacts, forming iron sulfide, FeS.
- Different color, not magnetic.
Iron sulfide has different properties than iron and sulfur.
Pure substances
Contain only one type of substance/chemical compound.
Examples
- Iron sulfide, FeS
- Water, H2O
- Gold, Au
- Sucrose, C12H22O11
Homogenous and heterogenous mixtures
Homogenous mixtures look the same, all the way through.
May be in gaseous, liquid or solid form.
Examples:
- Air
- Salt dissolved in water
- Bronze
Liquid homomgenous mixtures = solutions
Solid homogenous mixtures = alloys
A solution of salt in water is homogenous.
A bouillabaisse is a heterogenous mixture.
The classification of matter
Matter may be classified as mixtures or pure substances. These may be further classified as shown in the picture. Examples of each type is shown at the bottom.
Some separation techniques
When filtrating, a mixture of a solid and a liquid is poured over a filter. The solid stays on the filter while the liquid passes through.
In distillation, you take advantage of the fact that two mixed liquids have different boiling temperatures. The liquid with the lowest boiling temperature evaporates first, and is distilled off.
If two liquids don't mix, they may be separated using a separation funnel. The liquid with the highest density is poured out via the tap at the bottom.
If a solid substance is dissolved in a liquid, e.g. water, the two substances may be separated if the water evaporates.
