STATES OF MATTER - properties of gases and liquids (fluids) and solids
15. A particle model of dissolving a solid (solute) in a solvent to give a solution
Doc Brown's chemistry revision notes:
basic school chemistry science GCSE chemistry, IGCSE chemistry, O level and ~US grades 8, 9 and 10 school science courses or equivalent for ~14-16 year old science students for national examinations in chemistry and also helpful for UK advanced level chemistry students aged ~16-18 and US grades 11-12 K12 honors.
. Dissolving solids and solution formation
When a solid (the
solute) dissolves in a liquid (the
solvent) the resulting
called a solution. In general: solute +
solvent == dissolving ==> solution
In general: solute + solvent == dissolving ==> solution
So, the solute is what dissolves in a solvent, a solvent is a liquid that dissolves things and the solution is the result of dissolving something in a solvent.
The solid loses all its regular structure and the individual solid particles (molecules or ions) are now completely free from each other and randomly mix with the original liquid particles, and all particles can move around at random.
This describes salt dissolving in water, sugar dissolving in tea or wax dissolving in a hydrocarbon solvent like white spirit.
It does not usually involve a chemical reaction, so it is generally an example of a physical change.
Whatever the changes in volume of the solid + liquid, compared to the final solution, the Law of Conservation of Mass still applies, no loss or gain of the total mass of the system.
mass of solid solute + mass of liquid solvent = mass of solution after mixing and dissolving.
You cannot create mass or lose mass, but just change the mass of substances into another form.
If the solvent is evaporated, then the solid is reformed e.g. if a salt solution is left out for a long time or gently heated to speed things up, eventually salt crystals form, the process is called crystallisation.
Learning objectives for a particle models of solution formation
Be able to describe with particle model diagrams the difference between a solid, liquid and a solution.
Know what is meant by the words solvent, solute and solution and relate them to the particle model.
Know that the law of conservation of mass applies to the preparation of a solution (no loss or gain in mass, nothing disappears!).
Know what is meant by a homogeneous mixture i.e. here all the solid dissolves without any undissolved solid left over.
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