Dissolving

When a substance dissolves, it might look like it has disappeared, but in fact it has just mixed with the water to make a transparent (see-through) liquid called a solution.

Substances that dissolve in water are called soluble substances.

When you mix sugar with water, the sugar dissolves to make a transparent solution.

Salt is soluble in water too.

Substances that do not dissolve in water are called insoluble substances. For example, when you mix sand or flour with water, they do not dissolve.

Fascinating facts about dissolving!

• Dissolving is a reversible change.

• Temperature affects the rate at which a soluble substance dissolves.

• Stirring faster can also increase the rate at which a soluble substance dissolves through the addition of kinetic (motion) energy.

• We call the degree to which something dissolves it's solubility.

• Soluble substances include salt, soap and sugar.

• Insoluble substances include plastics, wood and metal.

When a substance dissolves, it might look like it has disappeared, but in fact it has just mixed with the water to make a transparent (see-through) liquid called a solution.

Substances that dissolve in water are called soluble substances. When you mix sugar with water, the sugar dissolves to make a transparent solution.

Salt is soluble in water too.

Substances that do not dissolve in water are called insoluble substances. For example, when you mix sand or flour with water, they do not dissolve.

Dissolving is a reversible change, which means that you can reverse the dissolving process to get the original solute back.

This is done by heating up the solvent until it reaches its boiling point and turns into a gas, this is called evaporation.

Once all the liquid has evaporated you are left with the solute that you started with.

Did you know?

The Dead Sea which is bordered by both Jordan and Israel, is nine times saltier than the ocean.

Like all seawater, the salt is soluble and has dissolved in the water.

The water in the Dead Sea is so salty there is very little animal or plant life that can survive in it. It is also naturally very buoyant, meaning that you can easily float on the surface.

Did you know?

You don't just have to wait for a substance (the solute) to dissolve, you can help it to dissolve faster by making the liquid (the solvent) hotter.

Stirring the solvent can also help to dissolve the solute faster because it helps to break up the solute into smaller pieces more quickly.

If you are using a hot solvent, such as hot water for coffee or hot chocolate, you might think that the solute that you are adding is melting.

However melting and dissolving are two different processes.

While you need heat for something to melt, dissolving can happen with or without heat.

Melting is when something changes state. This means it changes from a solid to a liquid, or a liquid to a gas when it is heated.

Dissolving is when something has been broken down into smaller particles and mixed with another substance to create a solution.

When you add sugar into a hot cup of tea the sugar doesn't melt because it doesn't change state from a solid into a liquid. It dissolves because the sugar is still in the solution. The sugar has just been broken down into tiny particles that have mixed in with the hot solvent, the tea.

If you added sugar to cold tea it would still dissolve but it would take much longer.

Did you know?

You cannot add an unlimited amount of a solute to a solvent.

If you add sugar to a glass of water the sugar will keep dissolving until the water reaches its saturation point (the maximum amount of the solute that the solution can dissolve).

After this, if you keep adding more sugar you will see it begin to settle in the bottom of the glass.

Dissolve – When a solid substance has mixed with a liquid to make a transparent (see-through) liquid.

Evaporation – When a liquid turns into a gas slowly, at temperatures below its usual boiling point.

Insoluble – Any substance that does not dissolve in water.

Melting – When something changes state from a solid to a liquid by using heat.

Mixture – Something that is created when you combine two or more things together.

Reversible change – A change that can be undone or reversed.

Separate – To split two substances up from one original substance.

Soluble – Substances that dissolve in water.

Solution – A type of mixture which is created when you dissolve a solid (or a liquid) into a liquid.

Substances – Any solid, liquid or gas with its own properties.

Solvent – A substance that dissolves other substances.

Tap on the different substances to find out what happens when you add them to water.