Separation Techniques - Filtration | Evaporation | Crystallisation

What is a mixture?

Two or more different types of substances that are mixed together in the same place and are not chemically joined.

What is formed when an insoluble solid is mixed with a liquid?

The solid doesn't dissolve; it just sinks to the bottom (e.g., sand and water).

What is a solution?

When one substance (the solute) dissolves in another substance (the solvent).

In a salt water solution, what is the solute, solvent, and solution?

Salt is the solute, water is the solvent, and salt water is the solution.

What does filtration separate?

Insoluble solids from liquids.

What does filter paper have that allows separation?

Lots of tiny holes that are small enough for liquid to pass through but not solids.

Can filtration separate a soluble solid from a liquid?

No.

What two techniques can separate a soluble solid from a solution?

Evaporation or crystallization.

How does evaporation work?

Heat the solution; the solvent evaporates, leaving dry crystals of the solid.

What is a problem with evaporation for some solids?

Some solids decompose when heated (thermal decomposition).

How does crystallization differ from evaporation?

Heat more gently (e.g., water bath), stop heating when crystals form, leave to cool, filter out crystals, then dry them.

Why does cooling the solution form more crystals?

Solids are less soluble at colder temperatures.

What are the final steps of crystallization after heating and cooling?

Filter out the crystals using filter paper and a funnel, then dry them (leave somewhere warm or in a drying oven).