 Solutions Solutes, Solvents & Solutions

Mixtures  You should be able to recall what a mixture is.  Two or more substances that are mixed together but not chemically bonded to each other.  Easiest example is saltwater or seawater  The proportion in a mixture is not fixed  If you have lots of salt or very little salt the mixture is still considered saltwater

Solutions  Solutions are mixtures in which soluble particles are completely dissolved in a liquid or a gas.  Made up of a;  Solute  Solvent  We will use coffee as an example of a solution  The substance that dissolves is called the solute  In this example the coffee granules  The substance that does the dissolving is called the solvent  In this example the hot water

Solutions Black Tea Mi-Wadi Seawater Wine Fizzy Drinks Substance SolventSolute Water Tea Flavours and Sugar Salt Flavours/Sugar/Carbon Dioxide Grape Juice and Alcohol Water is called the universal solvent, as it can dissolve many substances

Solvents  Water is described as the universal solvent  However there are other solvents  Ethanol  Acetone (Nail polish remover)  Toluene (Paint thinner)  Chloroform  Solvents can be dangerous  Think of the common hazard symbols  Toxic  Flammable  Irritant  Can cause significant health issues if abused

Solutions  Solutions do not have to be made from a solid and a liquid.  Solutions can also be made by dissolving a gas into a solvent.  Oxygen is dissolved in water allowing marine life to breathe  Solutions can also be made from a liquid mixing with another liquid  Alcohol is dissolved in wine, beer, etc.

Dilute vs Concentrated  We can change the strength of the solution, i.e. its taste, colour, smell, etc… by changing the amount of solute used.  A dilute solution has a small amount of solute in a large volume of solvent.  A concentrated solution has a large amount of solute in a small volume of solvent

Soluble vs Insoluble  If a substance is soluble it will dissolve in a liquid and if it is insoluble it will not dissolve  Calcium carbonate is not soluble in water because the calcium carbonate and water particles are not able to mix.  Copper sulfate is soluble in water because the copper sulfate and water particles are able to interact and mix together. Calcium Carbonate Copper Sulphate water

Immiscible Liquids  Liquids that do not mix together are called immiscible liquids  Examples are  Oil and water  Toluene and water  Gasoline and water  Liquids that do mix together are called miscible oil water

Suspensions  Suspensions are mixtures in which insoluble particles are suspended in a liquid or gas.  Examples of suspensions are;  Milk  Oil shaken in water  Dust in air  Sandy water Insoluble substance +Solvent=Suspension Sand+Water=Sandy water suspension

Conservation of Mass  If 10g of salt is added to 50g of pure water than the solution should have a mass of 60g. + = 50 g10 g + = 60 g

Solutions  The amount of solute that can dissolve in a solvent at a given temperature is called its solubility  The amount of a solute that can dissolve in a solvent can be increased by increasing a solvent’s temperature  This is generally true  A gas’ solubility decreases as the solvent temperature increases  Problem with the oceans warming due to climate change.  A solute will not dissolve in a solvent indefinitely.  Eventually it reaches a limit where no more will dissolve  At this point the solution is described as saturated

Solubility Curve Supersaturated solutions are very saturated indeed. The solute will stay in solution until a ‘seed’ crystal is added, and then it will crystallise out of the solution very quickly. When it does this, it gives out heat energy. Supersaturated solutions are therefore used in heat packs.