CSEC Chemistry • Lesson 3 of 4Mixtures, Solutions, Suspensions & Colloids · Myers Science Hub Student Centre
CourseCSEC Chemistry
Practice formatMCQ • Structured • Experimental
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Learning objectives
- Distinguish pure substances from mixtures using observable and particle-level evidence.
- Distinguish solutions, suspensions and colloids using sedimentation, filtration and light scattering.
- Identify common types of solutions.
- Interpret or plan an investigation of temperature and solubility.
Core notes
Mixture
Two or more substances physically combined. The components retain their properties and can be separated by physical methods.
Solution
A homogeneous mixture formed when a solute dissolves in a solvent. Solutions do not settle and their particles are too small to be removed by ordinary filtration.
Suspension
A heterogeneous mixture containing larger insoluble particles. The particles may settle and can usually be filtered.
Colloid
Particles are intermediate in size. Colloids do not settle readily and scatter a beam of light (Tyndall effect).
Types of solutions
| Type | Example |
|---|---|
| Solid in liquid | salt in water |
| Liquid in liquid | ethanol in water |
| Gas in liquid | carbon dioxide in soft drink |
| Solid in solid | alloy such as brass |
| Gas in gas | air |
Solubility and temperature
For many solid solutes, solubility increases as temperature increases. A solubility investigation must control the mass or volume of solvent and use a clear criterion for deciding when the solution is saturated.
Video lesson
Paper 01-style MCQ
1. Which observation best identifies a suspension rather than a true solution?KC • 1
2. Which mixture is an example of a gas dissolved in a liquid?KC • 1
3. A beam of light is visible as it passes through a mixture that does not settle. The mixture is most likely aUK • 1
Paper 02-style structured questions
4. Distinguish between a solution and a suspension. Give TWO differences.UK • 4
Any two valid paired differences, 2 marks each: solution is homogeneous while suspension is heterogeneous; solution particles do not settle while suspension particles may settle; solution passes through ordinary filter paper while suspended particles can be retained; a true solution does not show visible scattering like many colloidal/suspended systems.
5. A student adds increasing masses of potassium nitrate to 50 cm³ of water at 20 °C until no more dissolves. Explain how the student could determine the solubility in g per 100 g of water.UK • 4
Determine the maximum mass of solute that dissolves (1); convert 50 cm³ water to approximately 50 g where appropriate (1); scale the dissolved mass to 100 g water (1); state the solubility with unit g per 100 g water at 20 °C (1).
Experiment-type question
6. Design an investigation to determine how temperature affects the solubility of a solid in water.XS/PD • 8
State a testable aim/hypothesis (1); independent variable = temperature (1); dependent variable = mass of solute dissolving in a fixed amount of water (1); keep water mass/volume, solute identity and mixing method constant (1); use several temperatures and determine saturation at each (1); repeat/average where practical (1); plot solubility against temperature (1); include a safety precaution for heating/hot glassware (1).