Making and separating solutions

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Lesson notes

Solutions and Dissolving

When a **solute** dissolves in a **solvent**, a **solution** forms.
Sugar and salt are **soluble** in water; sand is **insoluble** in water.
Dissolving happens because solute particles mix evenly with solvent particles.
Stirring and **heating** the solvent make a solute dissolve faster.

Separating a Soluble Solid from a Solution (Evaporation)

To obtain a dissolved solid (e.g., copper sulphate), evaporate the solvent.
Pour the solution into an **evaporating basin** and heat gently.
As the solvent evaporates, **crystals** of the solute form.
Remove from heat when enough solvent has evaporated, then leave to crystallise.

Separating an Insoluble Solid from a Liquid (Filtration)

Use **filtration** to separate an insoluble solid (e.g., sand) from a liquid.
Pour the mixture through **filter paper** in a funnel.
Liquid particles (small) pass through the paper; solid particles (larger) are trapped.
The liquid that passes through is called the **filtrate**; the trapped solid is the **residue**.

Particle arrangement in solids, liquids, and gases. Dissolving involves particles mixing, not changing state.

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Practice questions

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1.Which of the following is true about sand and water?
Easy
- ASand is soluble in water.
- BSand is insoluble in water.
- CSand dissolves in water to form a solution.
- DSand and water cannot be separated by filtration.
2.What is the solute in a fizzy drink where carbon dioxide is dissolved in water?
Easy
- AWater
- BCarbon dioxide
- CFizzy drink
- DSugar
3.Which of the following best defines the term 'soluble'?
Easy
- AA substance that cannot dissolve in a solvent
- BA substance that can dissolve in a solvent
- CA liquid that dissolves other substances
- DA mixture of a solute and a solvent
4.Which of the following best defines the term 'insoluble'?
Easy
- AA substance that can dissolve in a solvent
- BA substance that cannot dissolve in a solvent
- CA liquid that dissolves other substances
- DA mixture that cannot be separated
5.Which two methods can make sugar dissolve faster in water?
Easy
- AHeating and stirring
- BCooling and stirring
- CHeating and leaving still
- DAdding more sugar and cooling
6.How would you separate sand from a mixture of sand and water?
Medium
- AEvaporation
- BDistillation
- CFiltration
- DChromatography
7.Which method is used to obtain sugar crystals from a sugar solution?
Medium
- AFiltration
- BEvaporation
- CDistillation
- DDecanting
8.In a solution of salt water, which component is the solvent?
Medium
- ASalt
- BWater
- CBoth salt and water
- DNeither

More questions

9.A student adds copper sulfate crystals to water and stirs. After some time, the crystals disappear. Which statement is correct?
Medium
- AThe copper sulfate has chemically reacted with water.
- BThe copper sulfate has dissolved, forming a solution.
- CThe copper sulfate has evaporated.
- DThe copper sulfate has become insoluble.
10.A mixture of salt, sand, and water is stirred and then filtered. What remains on the filter paper?
Hard
- ASalt and sand
- BSand only
- CSalt only
- DNothing
11.Which of the following statements about solutions is correct?
Hard
- AA solution always contains a solid solute and a liquid solvent.
- BThe solute is the substance that dissolves the solvent.
- CA solution is a mixture of a solute dissolved in a solvent.
- DAll solutes are soluble in water.
12.To obtain copper sulfate crystals from a copper sulfate solution, the solution is heated gently in an evaporating basin. Why is the solution removed from heat before all the water has evaporated?
Hard
- ATo prevent the copper sulfate from decomposing
- BTo allow the remaining water to evaporate slowly at room temperature
- CTo avoid the copper sulfate from boiling over
- DTo speed up the formation of crystals
13.A student adds 10 g of salt to 100 cm³ of water at 20°C and stirs. After 5 minutes, all the salt has dissolved. The student repeats the experiment with 100 cm³ of water at 60°C. Which statement about the second experiment is correct?
Medium
- AThe salt dissolves faster because the water is hotter.
- BThe salt dissolves slower because the water is hotter.
- CThe salt does not dissolve because the water is too hot.
- DThe salt dissolves at the same rate because the amount of salt is the same.
14.A mixture contains salt, sand, and water. The mixture is stirred and then filtered. The filtrate is collected and then heated gently in an evaporating basin until some water has evaporated. What is the final residue in the evaporating basin?
Hard
- ASalt crystals
- BSand
- CSalt and sand
- DWater and salt
15.The diagram shows an experiment to obtain copper sulfate crystals from a copper sulfate solution. The solution is heated gently in an evaporating basin. Why is the solution removed from heat before all the water has evaporated?
Medium
- ATo prevent the copper sulfate from decomposing
- BTo allow the remaining water to evaporate slowly at room temperature
- CTo speed up the formation of crystals
- DTo avoid boiling the solution
16.Which of the following is the solute in a solution made by dissolving oxygen gas in water?
Easy
- AOxygen
- BWater
- COxygen and water
- DAir
17.A student has a mixture of iron filings and sand. Which method should be used to separate them?
Medium
- AFiltration
- BEvaporation
- CUsing a magnet
- DDistillation
18.A student adds 5 g of sugar to 50 cm³ of water at 25°C and stirs. After 2 minutes, undissolved sugar remains at the bottom. Which change would cause all the sugar to dissolve in less than 2 minutes?
Hard
- AUsing 100 cm³ of water at 25°C
- BUsing 50 cm³ of water at 50°C
- CAdding 10 g of sugar to 50 cm³ of water at 25°C
- DStirring the mixture more slowly
19.Which of the following is insoluble in water?
Easy
- ASalt
- BSugar
- CSand
- DOxygen
20.A student filters a mixture of sand and water. What passes through the filter paper?
Medium
- ASand and water
- BWater only
- CSand only
- DNeither sand nor water
21.A solution contains 20 g of salt dissolved in 100 g of water. The solution is heated until 50 g of water has evaporated. Assuming no salt is lost, what mass of salt crystals will be obtained?
Hard
- A20 g
- B10 g
- C30 g
- D5 g
22.In a solution of sugar in water, what is the solvent?
Easy
- ASugar
- BWater
- CSugar and water
- DNone of the above
23.A student wants to obtain salt crystals from a salt solution. Which piece of apparatus is essential for this process?
Medium
- AFilter funnel
- BEvaporating basin
- CThermometer
- DMeasuring cylinder
24.A mixture of salt, sand, and water is stirred and then filtered. The filtrate is collected and then heated gently in an evaporating basin until some water has evaporated. What remains on the filter paper?
Hard
- ASand only
- BSalt only
- CSand and salt
- DSalt and water
25.A student wants to obtain copper sulfate crystals from a copper sulfate solution. Which of the following is the correct sequence of steps?
Medium
- AHeat the solution strongly until all the water has evaporated, then collect the crystals.
- BPour the solution into an evaporating basin, heat gently until some water evaporates, then leave to cool and crystallise.
- CFilter the solution to remove impurities, then heat the filtrate to dryness.
- DAdd more water to the solution, then heat until crystals form.
26.A student has a mixture of sand and water. Which method should be used to separate them?
Medium
- AEvaporation
- BFiltration
- CDistillation
- DCrystallisation
27.In a fizzy drink, carbon dioxide is dissolved in water. What is the solute?
Easy
- AFizzy drink
- BCarbon dioxide
- CWater
- DBubbles
28.A student adds 10 g of salt to 100 cm³ of water at 20°C and stirs. After 5 minutes, all the salt has dissolved. The student repeats the experiment with 100 cm³ of water at 50°C and adds salt until no more dissolves. Which statement is correct?
Medium
- AMore salt dissolves in the hot water because the salt particles are smaller at higher temperatures.
- BMore salt dissolves in the hot water because the particles move faster and the solvent can hold more solute.
- CThe same amount of salt dissolves in both because solubility is constant.
- DLess salt dissolves in the hot water because the water evaporates faster.
29.A mixture contains salt, sand, and water. The mixture is stirred and then filtered. The filtrate is collected and then heated gently in an evaporating basin until some water has evaporated. Which substances are obtained after filtration and after evaporation?
Hard
- AFiltration: sand on filter paper; evaporation: salt crystals left in basin
- BFiltration: salt and sand on filter paper; evaporation: water collected
- CFiltration: salt in filtrate; evaporation: sand left in basin
- DFiltration: sand in filtrate; evaporation: salt crystals left in basin
30.A solution contains 20 g of salt dissolved in 100 g of water. The solution is heated until 50 g of water has evaporated. Assuming no salt is lost, what mass of salt remains in the solution?
Medium
- A10 g
- B20 g
- C30 g
- D70 g
31.Which of the following best defines the term 'solute'?
Easy
- AA substance that dissolves in a solvent
- BA substance that dissolves other substances
- CA mixture of a solute and a solvent
- DA substance that does not dissolve
32.Which of the following best defines the term 'solvent'?
Easy
- AA substance that dissolves in a solute
- BA substance that dissolves other substances
- CA mixture of a solute and a solvent
- DA substance that does not dissolve
33.Which of the following best defines the term 'solution'?
Easy
- AA substance that dissolves in a solvent
- BA substance that dissolves other substances
- CA mixture formed when a solute dissolves in a solvent
- DA substance that does not dissolve
34.Which of the following statements is true?
Easy
- ASand is soluble in water.
- BSalt is soluble in water.
- CSugar is insoluble in water.
- DSand dissolves in water.
35.Can you filter out salt from a saltwater solution using filter paper?
Easy
- AYes, because salt particles are larger than water molecules.
- BNo, because salt is dissolved and the particles are too small to be trapped.
- CYes, because salt is insoluble in water.
- DNo, because filter paper only separates gases.
36.In a fizzy drink, carbon dioxide is dissolved in water. What is the solvent?
Easy
- AWater
- BCarbon dioxide
- CFizzy drink
- DSalt
37.Which of the following methods is used to separate sand from a mixture of sand and water?
Medium
- AEvaporation
- BDistillation
- CFiltration
- DChromatography
38.To obtain sugar crystals from a sugar solution, which method is used?
Medium
- AFiltration
- BEvaporation
- CDecanting
- DDistillation
39.A student adds 10 g of salt to 100 cm³ of water at 20°C and stirs. After 5 minutes, all the salt has dissolved. The student repeats the experiment with 100 cm³ of water at 50°C. Which statement best describes what happens?
Hard
- AThe salt dissolves more slowly at 50°C.
- BThe salt dissolves at the same rate at both temperatures.
- CThe salt dissolves more quickly at 50°C.
- DThe salt does not dissolve at 50°C.
40.A mixture contains salt, sand, and water. The mixture is stirred and then filtered. What is collected as the filtrate?
Hard
- ASand only
- BSalt only
- CSalt and water
- DSand and water

Revision notes

## Making and Separating Solutions - **Dissolving**: When a substance (solute) mixes evenly in another (solvent) to form a **solution**. Example: sugar (solute) in water (solvent). - **Speed up dissolving**: Heat the water and/or stir. - **Soluble**: Can dissolve. **Insoluble**: Cannot dissolve. Example: salt is soluble in water; sand is insoluble. - **Separating soluble solute from solvent**: Use **evaporation**. Heat the solution in an evaporating basin. The solvent evaporates, leaving crystals of the solute (e.g., copper sulphate crystals). - **Separating insoluble solid from liquid**: Use **filtration**. Pour mixture through filter paper. Liquid (filtrate) passes through; solid (residue) stays on the paper. Example: sand and water. **Key points**: - Solute + Solvent → Solution - Soluble = can dissolve; Insoluble = cannot dissolve - To separate a dissolved solid: evaporate the solvent - To separate an undissolved solid: filter the mixture

Solute: A substance that dissolves in a solvent.
Solvent: A substance that dissolves other substances.
Solution: A mixture formed when a solute dissolves in a solvent.
Soluble: Able to dissolve in a solvent.
Insoluble: Not able to dissolve in a solvent.
Evaporation: A method to separate a dissolved solid from a solution by heating to remove the solvent.
Filtration: A method to separate an insoluble solid from a liquid using a filter.

Flashcards

What is a solute?

A substance that dissolves in a solvent.

What is a solvent?

A substance that dissolves other substances.

What is a solution?

A mixture formed when a solute dissolves in a solvent.

What does soluble mean?

A substance that can dissolve in a solvent.

What does insoluble mean?

A substance that cannot dissolve in a solvent.

Give an example of a soluble substance in water.

Sugar or salt.

Give an example of an insoluble substance in water.

Sand.

What happens to sugar particles when it dissolves in water?

The sugar particles mix with the water particles and seem to disappear.

Name two ways to make sugar dissolve faster in water.

Heat the water and stir it.

How can you separate salt from a saltwater solution?

By evaporation: heat the solution until the water evaporates, leaving salt crystals.

How can you separate sand from a sand and water mixture?

By filtration: pour the mixture through filter paper; water passes through, sand is trapped.

Why does filtration work for sand and water but not for salt and water?

Sand particles are larger than the pores in filter paper, but salt particles (ions) are smaller and pass through.

In a sugar and water solution, what is the solute?

Sugar.

In a sugar and water solution, what is the solvent?

Water.

In a fizzy drink, carbon dioxide is dissolved in water. What is the solute?

Carbon dioxide.

In a fizzy drink, carbon dioxide is dissolved in water. What is the solvent?

Water.

True or false: Sand is soluble in water.

False.

True or false: Salt is soluble in water.

True.

True or false: Sugar dissolves faster in hot water than in cold water.

True.

True or false: You can filter out salt from a saltwater solution using filter paper.

False.

Describe how to obtain copper sulphate crystals from a solution.

Pour the solution into an evaporating basin, gently heat until some solvent evaporates, then remove from heat. Crystals form as the solvent continues to evaporate.

Why does evaporation work to separate a solute from a solution?

The solvent evaporates, leaving the solute behind as solid crystals.

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