Properties and Changes of Matter
Everything around you is matter, and every piece of matter can be described and can change. Learning to describe matter by its properties, and to tell a physical change from a chemical one, is one of the most testable skills in all of science. It also explains everyday things, like why ice melting is reversible but a log burning is not.
This lesson sorts out properties versus changes, and physical versus chemical, with clear signs you can use on a test.
A property is a trait you can use to describe or identify matter, such as color, density, or how it reacts with acid. A physical change alters the form of a substance without making a new substance, like melting or cutting. A chemical change produces one or more new substances, like burning or rusting. New substance means chemical change.
What is the difference between physical and chemical properties?
A physical property can be observed without changing what the substance is. Color, texture, boiling point, density, and state (solid, liquid, gas) are all physical properties. A chemical property describes how a substance reacts to form something new, such as flammability or the ability to rust. You often have to try to change the substance to see a chemical property.
Density is a favorite on tests because it stays the same no matter how much of the substance you have. A small gold ring and a large gold bar have the same density, which is why density helps identify what a material actually is.
How can you tell a physical change from a chemical change?
In a physical change, the substance looks different but is still the same material. Melting ice, boiling water, dissolving sugar, and tearing paper are physical changes; the water and the paper are still water and paper. Most physical changes can be reversed.
In a chemical change, the atoms rearrange into new substances with new properties. Watch for telltale signs: a color change, a gas forming (bubbles), a solid forming from liquids, light or heat given off, or an odor appearing. Burning, rusting, and food spoiling are chemical changes, and they are usually hard to reverse.
| Change | Type | Why |
|---|---|---|
| Ice melting | Physical | Still water, just a new state |
| Iron rusting | Chemical | New substance (iron oxide) forms |
| Chopping wood | Physical | Still wood, only smaller |
| Baking a cake | Chemical | New substances form; cannot un-bake |
What about the law of conservation of mass?
Whether a change is physical or chemical, matter is never created or destroyed. If you seal a candle in a jar and burn it, the total mass of everything in the jar stays the same, because the atoms only rearrange. This idea, the conservation of mass, underlies all of chemistry and shows up again when you study chemical reactions.
Watch: A Short Video Lesson
Miacademy Learning Channel walks through this skill clearly in a few minutes. It is a helpful companion to the reading above:
A routine for property and change questions
- Decide whether the question is about a property (a description) or a change (something happening).
- For a property, ask whether you must change the substance to see it. If yes, it is a chemical property.
- For a change, ask whether a brand-new substance formed.
- Look for chemical-change clues: color change, gas, odor, light, heat, or a solid forming.
- If the change can be easily reversed and no new substance appears, it is physical.
Practice questions
- Is boiling water a physical or a chemical change?
- Which of these is a chemical property: color, density, or flammability?
- Name two signs that a chemical change has happened.
- A nail left outside turns orange and flaky. Physical or chemical change?
- Why is density a useful property for identifying a material?
- True or false: matter can be destroyed during a chemical change.
Answers:
- Physical. The water becomes steam but is still water.
- Flammability, because you must burn the substance to observe it.
- Any two of: color change, gas bubbles, odor, light or heat released, a solid forming.
- Chemical. Rust is a new substance.
- Because density stays the same for a material no matter the amount, so it helps identify what the material is.
- False. Mass is conserved; atoms only rearrange.
Where this fits
Properties and changes set up the study of what matter is made of, so they lead straight into states of matter and phase changes and the atoms that do the rearranging. You can measure many of these properties using the tools from measurement and instruments. Every topic is organized on the ASVAB General Science Learning Hub.
Recommended Prep Books
These study guides and practice books help you keep building momentum as you prepare:
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