Properties of Matter

Every kind of matter has properties — the features that describe what it is and how it acts. Scientists use properties to identify substances, sort them into groups, and predict what they will do in different conditions.

Physical Properties

A physical property is something you can observe or measure without changing what the substance is. If you weigh a block of iron or measure its length, the iron is still iron afterward. Common physical properties include mass, volume, density, color, hardness, magnetism, and electrical conductivity.

• Mass — how much matter an object contains, measured in grams (1 g ≈ 0.035 oz).
• Volume — how much space the object takes up, measured in milliliters or cubic centimeters (1 mL ≈ 0.034 fl oz).
• Density — mass per unit volume; tells you whether something will sink or float.
• Hardness — how easily a material is scratched or dented.
• Magnetism — whether the material is attracted to a magnet.
• Conductivity — how well heat or electricity moves through the material.

Chemical Properties

A chemical property describes how a substance behaves when it changes into a new substance. You can only see a chemical property by causing — or trying to cause — a chemical reaction. Wood burning, iron rusting, and milk turning sour are all examples of chemical properties at work.

• Flammability — whether the substance will burn in air.
• Reactivity with acid — whether the substance fizzes or dissolves in acid.
• Reactivity with oxygen — whether it rusts, tarnishes, or oxidizes.
• Toxicity — whether it reacts in harmful ways with living things.

Telling Them Apart

Ask one question: did the substance turn into something new? If the answer is no, the property you observed is physical. If the answer is yes — a new substance was formed — the property is chemical.