Identifying substances using properties Sect 2 3 Substances

Identifying substances using properties Sect. 2. 3

Substances have different properties We look at different physical properties to identify what a substance is. Sometimes we do not know what a substance is, so we must compare different properties of an unknown substance to a known substance.

Properties used to identify a substance Certain properties are used to identify substances because they do not vary from sample to sample. We use the following properties to identify substances: density, heating properties, solubility, electric properties and magnetic properties.

Density Scientist know different densities of many substances. We can compare the density of an unknown substance to a known density. Many substances may have the same density, so other properties are needed to be tested.

Heating Properties Substances respond to heat differently. You can measure the rate at which a substance conducts heat and compare that rate with the rates of other substances.

Solubility A measure of how much of a substance dissolves in a given volume of a liquid. Ex: Salt will dissolve in water easily, but dirt will not.

Electric Properties Some substances conduct electricity better than others. This means that they allow electric charge to move through them easily. Example: Copper is an excellent conductor while rubber is not We test to see whether or not a substance can conduct electricity and how much electricity it can conduct.

Magnetic Properties Some elements are attracted to magnets and some are not. Metals such as iron, cobalt and nickel are magnetic, however copper, zinc and aluminum are not.

We can separate mixtures by using the properties of the substances in them. Depending on what state of matter the mixture is will depend on how you separate the mixture. If you have two metals, you can try to separate them using magnets. If you have a solid in a liquid, a filter can separate them. If a solid’s particles are too small to use a filter, then evaporating the liquid can separate them.