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Solutions
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When you stir sugar into tea or salt into water the solid dissolves in the liquid to form a mixture we call a solution.
A liquid that can dissolve substances in this way is called a solvent, …
Solvent: Liquid that dissolves a solid
… whilst the solid that dissolves is called the solute; we say it is soluble.
Solute = substance dissolved in a solution
Even though it looks as if it’s disappeared, the solute still exists within the mixture.
Salt solution has the same mass as the salt and water separately, showing the salt is still very much present.
The same occurs when sugar dissolves in water. The water consists of many tiny particles, moving around inside its container.
When the solid crystals of sugar are added, they break up into tiny sugar particles.
These move around freely, between the water particles, so the volume of the solution stays roughly the same.
Dissolving is not a chemical reaction – the particles themselves are unchanged and no new substances are made.
It’s purely a physical process, which causes the particles to mix together.
The more solute that dissolves, the more concentrated the solution becomes.
But whatever its concentration, a solution always looks clear.
Solutions can still be coloured, but are always transparent because the dissolved solid particles are too small to see.
Insoluble
We know something hasn’t dissolved if the mixture stays cloudy.
Many solids don’t dissolve in water. We say they’re insoluble, such as this clay.
This dye won’t dissolve in water, however much it’s stirred.
And nail varnish is insoluble in water, but will dissolve in acetone.
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Solutions
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Saturation
If more solute is added to a solution, there’s always a point where it can no longer dissolve.
This is called saturation.
How quickly a solute dissolves will also depend on the temperature. The hotter the liquid, the quicker the particles move around.
So sugar in a hot cup of tea will dissolve much more quickly than in cool water.
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&file=HullFund9eCh08ProblemSolutions
1 DETERMINE WHETHER SOLUTIONS EXIST FOR EACH OF THE
11 BUFFER SOLUTIONS INTRODUCTION ANY SOLUTION THAT CONTAINS BOTH
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