1Dissolving
When sugar dissolves, its particles break away and spread out between the water particles. They are still there, but each one is far too small to see.
dissolve
Lesson 8.2 notes
Dissolving and solubility
Solutes, solvents and solutions, and why some things dissolve faster or more than others.
2Solute, solvent, solution
The solute dissolves in the solvent to make a solution. In salt water, salt is the solute and water is the solvent.
solutesolventsolution
3Mass is conserved
100 g of water and 10 g of sugar make 110 g of solution. No particles are lost when something dissolves.
conservation of mass
4Soluble or insoluble
Salt is soluble in water: it dissolves. Sand is insoluble: its grains stay whole and sink.
solubleinsoluble
5Saturated solutions
Keep adding a solute and eventually no more will dissolve. The solution is saturated.
saturated
6Solubility and temperature
Solubility is the most of a solid that can dissolve in 100 g of water at a given temperature. For most solids it rises as the water gets hotter.
solubility
7Dissolving faster
Solids dissolve faster in warmer water, when they are stirred, and when they are in smaller pieces.
rate of dissolving
Explore: Solubility lab
Pick a solid, set the temperature, and add it 10 g at a time until no more dissolves.
Common mistake: Dissolving is not melting
Melting needs heat and happens to a substance on its own. Dissolving needs a solvent: the solute's particles spread out between the solvent's particles. Sugar in tea dissolves; butter in a pan melts.
Remember
- Solute + solvent → solution. The mass is conserved.
- Soluble substances dissolve; insoluble ones don't. A solution is see-through.
- A saturated solution can't dissolve any more. Solubility usually rises with temperature.
Going further at GCSE