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⚗️ Pure Substances and Mixtures

From solid gold to muddy rivers: discover what makes a substance pure and how to pull a mixture apart.

lessons

~20 min

to learn

🔬 Science

subject

Teens

level

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What you’ll learn

Pure SubstancesUnderstand that a pure substance is made of only one type of particle, and can be an element or a compound.A pure substance is made of only one type of particle. Elements like gold and oxygen are pure substances that cannot be broken down further. When elements chemically join they form compounds, like pure water or salt, which are also pure substances because they are one type of particle throughout.
MixturesUnderstand that a mixture is two or more substances physically mixed but not chemically joined, including solutions.A mixture is two or more substances mixed together but not chemically joined, so each keeps its own properties and can be separated again. Salt water is a solution, where a solid dissolves evenly in a liquid, while muddy water holds bits that do not dissolve. Air is a mixture of gases.
Separating MixturesLearn how filtering, evaporation, distillation, and chromatography separate different kinds of mixtures.Mixtures can be separated by physical methods. Filtering traps solids that do not dissolve, evaporation leaves a dissolved solid like salt behind, distillation collects the liquid such as pure water, and chromatography separates coloured dyes. The method you choose depends on what you want to get back.

Questions this course answers

What is a pure substance?

A pure substance contains only one type of particle, such as an element or a compound.

What is a compound?

A compound forms when two or more elements are chemically joined, and it is still a pure substance.

What makes something a mixture rather than a compound?

In a mixture the substances are only physically mixed, not chemically joined, so each keeps its own properties.

Salt water is an example of a solution. What is it?

A solution is a mixture where a solid dissolves evenly in a liquid, like salt in water, and it can be separated again.

How would you separate sand from water?

Sand does not dissolve, so filtering traps the solid sand while the water passes through.

Which method would you use to get pure water back from salt water?

Distillation boils the water into vapour and cools it back to liquid, collecting pure water and leaving the salt behind.

Grounded in trusted sources

Royal Society of Chemistry
BBC Bitesize
Britannica

Every Wunder lesson is built from real, reputable sources — never invented.

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