SolutionsSolutions

Aim: To understand the concept of solutionsAim: To understand the concept of solutions

At the end of this section you will know:At the end of this section you will know:

Terms, solvent, solute, solution + examples (2)Terms, solvent, solute, solution + examples (2)

Difference between melting and dissolvingDifference between melting and dissolving

Terms suspension, Terms suspension, dilute, concentrateddilute, concentrated

Explain concentration with particle theory.Explain concentration with particle theory.

Saturated solution, solubility with temp.+e.g.(2)Saturated solution, solubility with temp.+e.g.(2)

How solubility is measured. How to graph solubility against How solubility is measured. How to graph solubility against temperature (solubility curve). Must be able to read graph. temperature (solubility curve). Must be able to read graph.

Crystallisation, different type of solutes/ solvents (3) Dangers Crystallisation, different type of solutes/ solvents (3) Dangers of other solvents (3)of other solvents (3)

KeywordsKeywords

SolutionsSolutions

Clear mixtures in which parts are too small Clear mixtures in which parts are too small to be seen and do not settle.to be seen and do not settle.

Consist of 2 parts:Consist of 2 parts: Solvent: does the dissolving e.g water, nail Solvent: does the dissolving e.g water, nail

varnish remover.varnish remover. Solute: is dissolved e.g. sugar, nail varnishSolute: is dissolved e.g. sugar, nail varnish Solution = mixture of solute and solventSolution = mixture of solute and solvent

Examples of SolutionsExamples of Solutions

Minerals are solutions ofcarbon dioxide, sugar,and flavorings dissolvedin water.

An alloy is a solidsolution of metals.

What increases how much What increases how much dissolves?dissolves?

Crushing the Crushing the solutesolute

Heating the Heating the solvent, if you solvent, if you are dissolving a are dissolving a solid in a liquidsolid in a liquid

Stirring the Stirring the solutionsolution

What is a suspension?What is a suspension?

When a finely divided solid is When a finely divided solid is scattered throughout a liquid scattered throughout a liquid you have a suspension.you have a suspension.

Any liquid you have to shake Any liquid you have to shake before use is a suspension. e.g before use is a suspension. e.g milk of magnesia, milk, mud milk of magnesia, milk, mud and water. and water.

Concentrated SolutionsConcentrated Solutions

Concentrated solutionsConcentrated solutions have more solute and less solvent. have more solute and less solvent. e.g Orange juice or blackcurrent juice you buy in the e.g Orange juice or blackcurrent juice you buy in the supermarket to dilute for drinking.supermarket to dilute for drinking.

Dilute SolutionsDilute Solutions

1)1) `̀When a solution has When a solution has little solute and alot of little solute and alot of solvent it is called a solvent it is called a dilute solution.dilute solution.

2)2) In the large beaker In the large beaker there are very few there are very few solute molecules so it solute molecules so it is a dilute solutionis a dilute solution

3)3) So how can a dilute So how can a dilute solution be made more solution be made more concentrated?concentrated?

Dilute SolutionsDilute Solutions

ANSWERANSWER

1)1) Add more solute.Add more solute.

2)2) Evaporate some of the Evaporate some of the solvent.solvent.

3)3) In the diagram the copper In the diagram the copper sulphate solution is made sulphate solution is made more concentrated by more concentrated by adding more copper adding more copper sulphate.sulphate.

Saturated, unsaturated, or Saturated, unsaturated, or supersaturated?supersaturated?

solutions hold the solutions hold the maximummaximum amount of solute at a given temperatureamount of solute at a given temperature

solutions are solutions are not not holding as holding as much as possible at that temperaturemuch as possible at that temperature

solutions are holding solutions are holding moremore than they should be able to at the than they should be able to at the given temperature.given temperature.

This solution is saturated. It is holding all it can, and we can see some undisolved solute.

Solubility and Solubility CurvesSolubility and Solubility CurvesFrom copper sulfate experiment you will have noticed that the copper sulfate dissolved easier in hot water than cold water.It is clear that the higher the temperature the more substance that dissolves.

Solubility = the mass of a substance in grams that will dissolve in 100g of solvent at a fixed temperature.

Solubility is different for different substances at the same temperature.

Solubility Curve Solubility Curve

Looking at the curve for Potassium Nitrate you can see that as the temperature rises the solubility rises rapidly.

For Sodium Chloride the rise in solubility with temperature is much slower.

Using Solubility CurvesUsing Solubility CurvesUse the results in the table

opposite to draw a solubility curve graph for Copper Sulfate.

Put temperatute on the horizontal axes

Put solubility of copper sulfate / 100g of water on the vertical axes.

Temp/oC CuSO4/100g

water

0 14

10 17

20 20

30 25

40 29

50 34

60 40

70 47

80 56

90 68

Solubility Curve GraphSolubility Curve Graph

Graph QuestionsGraph QuestionsHow much Copper Sulfate (CuSO

4) dissolves at 65oC

If the solution is cooled from 80oC to 20oC how much copper sulfate is put out solution to form crystals?

ANSWERSAt 65oC 43g of copper sulfate will dissolve in 100g of water.

At 80oC 56g of copper sulfate dissolves. At 20oC only 20g of copper sulfate dissolves. So if the solution is cooled 56 g – 20 g will come out of solution that is 36 g of crystals.

Solubility Curve GraphSolubility Curve Graph

56gAt80oC

20g at 20oC

CrystallisationCrystallisation

Crystallisation is the formation of crystals when a hot saturated solution is cooled or when solvent is evaporated from the solution.

Copper Sulphate Copper Sulphate crystalscrystals

Other types of solutionsOther types of solutions

Solutions are not always a solid solute in a liquid solvent e.g.

Fizzy drinks contain carbon dioxide (gas) dissolved in water.

Whiskey and other alcoholic drinks contain alcohol (liquid) dissolved in water.

Marshmallows contain air (gas) dissolved in sugar pastes (solid)

Other solventsAlcohol, chloroform, white spirit are solvents.

Dangers of other solventsDangers of other solventsSolvents used in paint are flammable.Solvents used in glue are extremely poisonous and can cause

damage to the brain, liver and other parts of the body.