Starter quiz
- What process happens when a solid can be observed to 'disappear' in a liquid to make a solution?
- boiling
- condensing
- melting
- dissolving ✓
- evaporating
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- When a process is able to go backwards, or be "undone", it is said to be ______.
- 'reversible' ✓
- Match the word to the definition.
- soluble⇔When a solid can dissolve in a liquid ✓
- insoluble⇔When a solid cannot dissolve in a liquid ✓
- solution⇔The mixture formed when a solid dissolves in a liquid ✓
- saturated⇔When no more solid can dissolve ✓
- Put the following changes of state for ice/water in order starting from the one that requires the lowest temperature to the one that requires the highest temperature.
- 1⇔Melting
- 2⇔Evaporating
- 3⇔Boiling
- A volume of salt solution containing 0.5 g of salt was placed in a beaker and left for 2 weeks on the windowsill, after which only crystals of salt remained. How much salt would be present?
- 0.0 g
- 0.25 g
- 0.4 g
- 0.5 g ✓
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- Sugar was added to water at 60℃ until no more sugar could dissolve. The solution was left to cool. What would you expect to see and why?
- No change as the sugar would still be dissolved.
- No change as temperature does not affect the solubility of the sugar.
- Solid sugar would start to form as the water would evaporate.
- Solid sugar would start to form as it is less soluble at a lower temperature. ✓
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Exit quiz
- What is a solute?
- A substance that has dissolved into a solvent. ✓
- A liquid into which a solute dissolves.
- A solid whose particles are arranged in an irregular pattern.
- A substance that undergoes evaporation.
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- Dissolving is a ______ process as solute can be added to the solvent and the solvent can then be evaporated to recover the solute.
- 'reversible' ✓
- Which definition best describes evaporation?
- Forms solid crystals from a saturated solution.
- Change from the liquid state to the gas state occurring at the boiling point.
- Change from the liquid state to the gas state occurring below the boiling point. ✓
- Forms solid crystals from a dilute solution.
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- What happens to the size of crystals formed during crystallisation if the solvent evaporates slowly?
- The crystals are smaller.
- The crystals remain the same size.
- The crystals are larger. ✓
- The crystals disappear.
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- What is the name of the process that forms solid crystals from a saturated solution by evaporating the solvent?
- 'crystallisation' ✓
- Solvents evaporate into the air during crystallisation. How does heating affect this process?
- It has no effect.
- It slows the process down.
- It speeds up the process. ✓
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Worksheet
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Lesson Details
Key learning points
- Evaporation can remove solvent from a solution, leading to the production of a saturated solution.
- Crystallisation reforms a solute as crystals from a saturated solution following a change in conditions.
- Solvents evaporate into the air around you during the process of crystallisation.
- Larger crystals form when the solvent evaporates more slowly.
- Heating a solution makes the solvent evaporate more quickly.
Common misconception
Pupils sometimes use the terms evaporation and boiling interchangeably, but they are not the same.
Boiling: a liquid substance is heated & gas bubbles form. Evaporation: same, BUT only on the surface of the liquid & the gas mixes with air.
Keywords
Solute - A solute is a substance that has dissolved into a solvent.
Solvent - A solvent is a liquid into which a solute dissolves.
Evaporation - Occurs when a substance's particles are in the liquid state at its surface with enough energy to change to the gas state and mix with air.
Crystallisation - A process that forms solid crystals from a saturated solution by evaporating the solvent.
Crystal - A crystal is a solid whose particles are arranged in a highly ordered, repeating pattern.
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