Separation of Substances: quick revision, 15 bites

Why We Separate Substances

Mixtures hide useful things — separation reveals them.

Most things around us are **mixtures**, not pure substances. Separating them gives us usable, safe and valuable components.

Takeaway. Separation turns a mixed, often unusable substance into clean, useful parts.

Pure Substance vs Mixture

One thing or many things — that's the difference.

Separation methods work because the parts of a mixture keep their **own properties**.

Takeaway. Mixtures can be separated by physical methods; pure substances cannot be split this way.

Handpicking and Threshing

Pick it out or beat it out.

Takeaway. Handpicking suits few, visible impurities; threshing separates grain from stalks.

Winnowing and Sieving

Wind and mesh do the sorting.

Takeaway. Winnowing uses weight difference; sieving uses size difference.

Sedimentation, Decantation and Filtration

Let it settle, pour it off, or filter it.

Takeaway. Sedimentation settles, decantation pours, filtration traps — together they clean muddy water.

Evaporation and Condensation

Boil it off, cool it back.

Takeaway. Evaporation recovers the dissolved solid; condensation recovers the liquid.

Using a Magnet to Separate

Magnets pull out only the magnetic bits.

A magnet separates **magnetic materials** like iron from non-magnetic ones like sand or sulphur.

Takeaway. Magnetic separation works only if one part of the mixture is magnetic.

Which Method for Which Mixture?

Match the method to the mixture.

Takeaway. Pick the method based on the property that differs — size, weight, solubility or magnetism.

Don't Confuse Decantation with Filtration

Pouring off is not the same as filtering.

Takeaway. Decantation pours; filtration traps — they do different jobs.

Evaporation Is Not Always the Answer

You can't evaporate to get the liquid back.

Takeaway. To keep both components, pair evaporation with condensation.

Separation in Everyday Life

You separate things every single day.

Takeaway. Separation methods are part of daily cooking, farming and water use.

Separation in Industry and Water Treatment

Big factories separate on a huge scale.

Takeaway. The same school-level methods scale up to run industries.

Quick Recall: Match Property to Method

Different property, different method.

Takeaway. Ask: which property is different? That decides the method.

Answering Separation Questions Well

Name the method, then justify it.

Takeaway. Method + property + reason = full-mark answer.

Salt Comes from the Sea

Your table salt was once seawater.

Most of the salt we eat is obtained by **evaporation of seawater** in shallow salt pans along the coast.

Takeaway. Evaporation is the simple science behind every pinch of salt.