Atoms & Molecules Matter Pure SubstancesMixtures & Solutions CompoundsElementsHeterogeneousHomogeneous

Definition: A substance that cannot be separated by a physical or mechanical process, (by hand or with a tool). Pure substances have a uniform composition – they look the same throughout and have the same chemical structure throughout. Its properties are constant throughout the entire substance. Examples: Salt, distilled water, diamond, oxygen.

Definition: A substance which can be separated by a physical or mechanical process, (by hand or with a tool). The properties of each substance in the mixtures are present and more or less evident. The composition of the mixture can be varied if the proportion of any of the substances is changed. There are two types of mixtures: homogeneous and heterogeneous. Examples: Soup, sea water, tap water, smoke, air, tea, etc.

Homogeneous or Solution: Definition: A mixture where the substances in the mixture are not visible to the naked eye. In appearance, homogeneous mixtures resemble pure substances because everything appears uniform. Examples – sugar and water, juice, clean air, steel, gold jewellery, tap water, alloys.

A solution, (same as homogeneous mixture), looks much like a pure substance. The difference is the number of particles that are present. If the particles are the same and uniform throughout the substance, it is a pure substance. If the particles are different, meaning that there are two types of particles, then it is a homogeneous mixture. Solutions have a property called soluble. This means that the particles in the solution have the ability to separate and spread out until they are uniform, making them homogeneous. Examples – sugar and salt are both soluble in water.

In a mixture, there are always at least two substances. In a solution, one is the solvent and the other is the solute. Solvent: The substance in the mixture that dissolves the other. There is always more solvent than there is solute. Water is usually a solvent. Solute: The substance in a mixture that is dissolved by the solvent. Salt and sugar are common solvents.

Solutions can exist is any state of matter: Solids Brass = copper and zinc. This is an alloy. Copper is the solvent, zinc is the solute. Liquids Vinegar = Acetic acid and water. Acetic acid is the solute, water is the solvent. Gases Air = Nitrogen, oxygen, carbon, etc. Nitrogen is the solvent, (70% of air), the others are solutes.

Heterogeneous: These mixtures are also made up of different substances, but these ones are visible to the naked eye. The particles are not evenly distributed and are not uniform. Examples – Vegetable soup, muddy water, concrete, $2 coin, salad.

Sometimes, it is necessary to separate mixtures. Filtering water to make it potable. To make new products. Separating food. There are many techniques used in order to separate mixtures. Sedimentation and Decantation Filtration Distillation Sifting

AKA – Settling and pouring When and how it works: When there are solids present within a liquid. To do it, you simply leave the mixture to settle for a few minutes or even days. Eventually, all of the solids will settle on the bottom of the container. Now, the liquid can be decanted, (poured), into a new container. Only possible with heterogeneous mixtures.

When and how it works: Only possible with heterogeneous mixtures. A filter must be present for filtration. Examples of filters are coffee filters, vacuum filters, and strainers.

When and how it works: Only possible with heterogeneous mixtures. This technique is used when large solids are in the mixture, (solid- solid or liquid-solid). A tool is needed: a sieve. Examples: Panning for gold Separating large rocks from the dirt.

When it works: Only useful for homogeneous mixtures. Because the particles are uniformly distributed, the other techniques will not work. How it works: Distillation depends on the characteristic properties of each substance in the mixture. Specifically, the boiling point. The homogenous mixture is heated to the boiling point of ONE substance. That substance will turn to gas and escape. This gas is trapped and the heat is removed. It will turn back into a liquid by condensation. The liquid will fall into a new container. The other part of the mixture does not boil. It remains in the original container.