Describing and Classifying Matter

Describing Matter

Each type of matter has its own unique properties. A property is a characteristic we can use to identify matter. We can use the properties of matter to know that wood is wood and gold is gold. The properties of matter fall into two categories. The first is physical properties. The second is chemical properties.

Physical Properties

A physical property is a way to describe the physical form of matter. We can identify some of these with our senses. Colour can be seen. So can luster. This is how shiny or reflective something is. Odour can be smelled. Some things, like acidity, can be tasted. Texture can be felt through touch. So can hardness and temperature. A person can try to flatten things to test their malleability. Or they can try to stretch things out to test their ductility.

Some properties can’t be identified through the senses. But they can be measured. Scientists do this without changing the matter. These properties include boiling point, melting point, electrical conductivity, magnetism and density.

Physical properties can be intensive or extensive.

An intensive property does not depend on the amount of matter. Colour, odour, density and melting point are intensive properties. An extensive property depends on the amount of matter. These include things like mass, volume and length.

Chemical Properties

A chemical property describes how likely it is the matter will go through a chemical reaction. Here are some examples of chemical properties:

Flammability

Flammability Is the ability of matter to burn or combust. Things that are flammable can ignite easily and burn quickly. Flammable matter is often called fuel.

Wood, gasoline and wax are all flammable.

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Shown is a diamond shape outlined in red on a white background. An illustration inside shows a large flame growing from a flat surface. The flame has two layers. The centre is white and the outside is black, as if it has grown large. A black bar along the bottom edge indicates a surface.

Corrosiveness

Corrosiveness is the ability of matter to ‘eat away’ another substance. It is important to wear safety equipment to protect your skin and eyes when using corrosive materials.

Corrosive materials include strong acids and bases. Hydrochloric acid and bleach are both corrosive.

Image - Text Version

Shown is a diamond shape outlined in red on a white background. An illustration inside shows liquid damaging skin and other materials. On the left, a test tube drips liquid onto a black bar, making a hole in it. The hole has jagged lines above it, indicating damage. On the right, a test tube drips liquid onto a hand. Jagged lines above indicate injury.

Toxicity

Is the ability of a material to cause damage to living things. Toxic materials cause harm when inhaled, swallowed or contact skin.

Lead, mercury, and chlorine gas are all toxic.

Image - Text Version

Shown is a diamond shape outlined in red on a white background. An illustration inside shows a skull and crossbones. The illustration is simplified. The human skull sits on a pair of long bones crossed in an X. It resembles the symbol used on pirate flags.

Classifying Matter

There are different ways to classify matter. One way is to classify it as a pure substance or a mixture.

Pure Substances

A pure substance is the same throughout. It can’t be separated into other substances, or transformed into a new substance.

The physical properties of a pure substance never change. Water is a pure substance. So, the boiling point of water is always 100 degrees Celsius at a pressure of 101.3 kilopascals.

Pure substances only contain one type of element or compound.

Elements

Elements are a type of pure substance. They contain only one type of atom. These include carbon (C), silver (Ag) and gold (Au). Scientists have organized the elements into a chart called The Periodic Table of Elements.

Click here to access screen reader Accessible Periodic Tables

Each element has a specific set of properties. These are called characteristic properties. Characteristic properties are all extensive. These include density, melting point, boiling point, electronegativity and atomic weight.

Did you know?

Currently, there are 118 known elements. Several of these elements were discovered during your lifetime!

Compounds

Compounds are another type of pure substance. Compound molecules contain two or more elements. These are held together by chemical bonds. For example, carbon dioxide molecules have one carbon atom and two oxygen atoms.

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Shown is a colour diagram of a molecule labelled O2 and a molecule labelled CO2 on a cream background.

The O2 diagram shows two blue spheres labelled "O", side-by-side. These are joined by two thick, black, horizontal lines.

The CO2 diagram has a red sphere labelled "C" in the centre, with one blue "O" sphere on either side. These are joined by two sets of thick, black, horizontal lines.

 

Compounds also have a fixed ratio. For example, a water molecule always has two hydrogen atoms (H) and one oxygen atom (O).

Compounds can be broken down into their individual elements. This is done through chemical reactions. For example, water can be broken down into hydrogen and oxygen using electrolysis.

The properties of a compound are different from the properties of each element it contains. Water has different properties than hydrogen or oxygen.

Mixtures

Mixtures are a physical combination of two or more pure substances. When they are mixed together, each pure substance keeps its own properties. For example, salt water does not have the same properties as either salt or water. It is not a white crystalline powder like salt. And it freezes at a lower temperature than water.

Mixtures can be either homogeneous or heterogeneous.

A homogeneous mixture has the same composition throughout. Salt water is a good example of a homogeneous mixture. This is because dissolved salt is spread evenly through the mixture.

Another name for a homogeneous mixture is a solution. Solutions can be made of liquids, gases or solids. Air is a solution made of gases. Alloys are solutions made of metals. These include bronze and brass.

A heterogeneous mixture is not the same throughout. The individual parts can be seen in these mixtures. Vegetable soup is a heterogeneous mixture. Each spoonful might include different vegetables, in different amounts. Heterogeneous mixtures also include things like salad dressing or mixed nuts.