​Mixtures are combinations of substances that are not chemically combined. Mixtures can occur in many states of matter-solids can mix with other solids or liquids, liquids can mix with other liquids or gases, and gases can mix with other gases. The components of mixtures can usually be separated by filtering or evaporation.

​

Solutions, such as sugar dissolved into water, are mixtures that are homogeneous, or evenly mixed. Alloys are solid solutions. Other mixtures are heterogeneous because the composition of the mixture differs from place to place in the mixture.

​

Mixtures also differ from compounds because their compositions can vary. Water is a simple compound. All water molecules have one oxygen and two hydrogen atoms. Granite is a mixture. Two samples of granite would each contain quartz, mica, and feldspar, but they may contain different amounts of each mineral.

​Mixtures can be separated by their physical properties, whereas compounds can only be separated chemically. Filtering can separate larger solid particles from liquids. Magnets can be used to separate iron and other materials that are attracted to magnets. Other physical properties, such as solubility, melting point, and density are also used to separate mixtures.

Method: Magnetism

• Used to Separate: Iron, Nickel, Cobalt

• Example: Iron and Sand

• Example: Steel and Plastic

Method: Sieve or Strainer

• Used To Separate: Larger Particles from Smaller Particles

• Example: Rocks from Sand

Method: Filter

• Used to Separate: Small Particles

• Example: Water from Sand

Method: Density

• Used to Separate: Floating or Sinking

• Example: Salt and Pepper in Water

Method: Boil

• Used to Separate: Water (Evaporation)

• Example: Water and Salt

Separating Several Types of Matter

• Multiple Methods Can Be Used

• Example: Filter & Evaporation/Boiling

Separating Mixtures is a Physical Change

All Materials Still Have the Same Properties!

​Matter can be changed physically or chemically. Physical changes do not change the chemical composition of a substance, but chemical changes do. Physical changes result in a change in at least one physical property of the substance, for example size, shape, or state. They do not change any of the chemical properties of a substance.

Water changing to ice is a physical change. Aluminum foil being crumpled and pressed into a small, hard lump is a physical change. Sugar dissolving into water is a physical change: the sugar is still sugar even though its molecules are suspended in water. Most physical changes can be reversed easily, such as evaporating the water from the sugar solution.

​PHYSICAL CHANGES

​CHEMICAL CHANGES

​On the other hand, chemical changes, such as rusting or burning, result in substances with new chemical and physical properties. Iron combines with oxygen to form rust. Carbon in paper or wood combines with oxygen to release heat and turn to ash. Chemical changes are not easily reversed.