Transcript Concentration and Solubility - Grade 7 Science is Awesome!

Concentration and
Solubility
Grade 7 Science: Pure Substances and Mixtures
Learning Goals / Success Criteria
 I can describe the concentration of a solution in
qualitative and quantitative terms.
 I can describe the difference between saturated and
unsaturated solutions.
 Key terms: concentrated solution, dilute solution,
concentration, saturated solution, unsaturated solution
Concentration and Solubility
 Did you know apple seeds contain tiny amounts of a
toxic chemical called cyanide? Eating a few of these
will not harm us, but eating a large amount will have an
effect on the human body.
 Pure substances can be good or bad for you depending
on how much of the substance you consume (think of
aspirin!).
 Doctors need to know how much of a substance there is
in a solution when prescribing medication.
Concentration and Solubility
 The words “concentrated” and “dilute” are used to describe how much
solute is in a certain volume of solution.
 Concentrated solution: a solution with a large number of
solute particles in a given volume of solution
 Dilute solution: a solution with a small number of solute
particles in a given volume of solution
Concentration and Solubility
Calculating Concentration
 Concentration: the amount of solute present in an
amount of solution
 The more solute dissolved, the greater the
concentration.
 This concentration can be expressed in mathematical
terms:
Suppose 100ml of solution contains 5.0g of sugar. The
concentration of sugar in that solution is 5.0g/100ml (a
ratio!).
Calculating Concentration
 The following is the equation for calculating
concentration:
 Concentration = mass of solute in grams
100 ml of solution
 Practice: Suppose a solution contains 6.0g of sugar in
200ml of solution. What is the concentration of the sugar
and water?
Saturated and Unsaturated Solutions
 What would happen if you were mixing Kool-Aid and
you kept adding drink powder?
 Eventually, no more powder would dissolve and the
solution would be saturated.
 Saturated solution: a solution in which no more solute
can dissolve
 Unsaturated solution: a solution in which more solute
can be dissolved
Solubility
 We now know there is a limit to the amount of solute that
can dissolve in a solvent. Chemists call this amount
solubility.
 Solubility: a measure of how much solute can dissolve in
a solvent to form a saturated solution at a particular
temperature and volume.
 Different solutes have different solubilities (e.g. sugar
dissolves more easily than salt) and different factors
affect solubility (something you will be exploring!)