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Mixing Substances 1

In this worksheet, students are given a chance to look over the basics about what happens when substances are mixed together: what is dissolving, how can substances be separated from each other, and are changes reversible?

'Mixing Substances 1' worksheet

Key stage:  KS 2

Curriculum topic:   Properties and Changes of Materials

Curriculum subtopic:   Dissolving and Solutions

Difficulty level:  

Worksheet Overview

QUESTION 1 of 10

When substances are mixed together some mix easily, others refuse to mix - how can you tell? Can they be separated from each other - and if so, how? Can the mixing be reversed?

 

 

Mixing beaker of solution

 

These are the sorts of questions that you'll be able to explore as you follow this worksheet through...

Glass of water

 

Which of these substances dissolve completely in water?

sugar

sand

flour

When a substance, like salt, dissolves completely what is the name of the liquid that is produced?

suspension

juice

solution

Now that it is dissolved in the water, in what form is the salt?

liquid

solid

gas

Is it possible to get the substance (like salt) back out of the liquid?

no, they're combined into a single substance now

yes, you boil it and collect the gas

yes, you evaporate the liquid away

When bicarbonate of soda is added to vinegar the two react together: the mixture fizzes and carbon dioxide gas is released.

 

Is it possible to reverse this reaction?

yes, you bubble the gas back through the liquid to get the vinegar and bicarbonate back again

no, gases are always released from irreversible reactions

no, new chemicals are formed so the reaction cannot be reversed

Which one of the following changes is NOT reversible?

your ice lolly melting on a hot day

baking dough into bread

dissolving a spoonful of coffee in water

For the following questions join Emily who is mixing different substances with water and observing whether they dissolve or not or whether something else happens.

 

Emily begins by stirring a Vitamin C tablet into water. After a minute or so it disappears and when she filters it nothing is left in the filter paper.

 

What happened to the Vitamin C tablet?

it dissolved in the water

it did not dissolve

it reacted with the water to make a new substance

Next Emily tried some Plaster of Paris which looks like a white powder. When she stirred it into the water she noticed it going lumpy and the water became very warm. When she filtered the mixture she found white lumps in the filter paper and the liquid dripping through was colourless.

 

What happened to the Plaster of Paris?

it dissolved in the water

it did not dissolve

it reacted with the water to make a new substance

Next Emily asked her gran for one of the special tablets she used for cleaning her dentures (false teeth). Emily popped the tablet into some water: it fizzed and turned the water pink - it also smelled funny, sort of fruity and minty at the same time.

 

When she filtered the liquid there was nothing much left in the filter paper and a pink liquid dripped out.

 

What happened to the denture-cleaning tablet?

it dissolved in the water

it did not dissolve

it reacted with the water to make a new substance

Emily went into her bedroom and got out her Chemistry set - she thought it would be fun to try adding some chemicals from there to the water. She checked the instruction booklet to make sure that none of them would be dangerous.

 

She decided to try a lovely blue crystal called COPPER SULPHATE. She stirred a spoonful into her water and observed that after a minute all the crystals had disappeared to leave a pretty blue liquid.

 

She filtered the blue liquid which passed through the filter paper leaving nothing behind.

 

What happened to the copper sulphate crystals?

they dissolved in the water

they did not dissolve

they reacted with the water to make a new substance

  • Question 1

Glass of water

 

Which of these substances dissolve completely in water?

CORRECT ANSWER
sugar
EDDIE SAYS
Flour makes a yukky mess with water(actually, it's a good homemade paste!) and sand refuses to dissolve (there wouldn't be beaches otherwise!), so it's sugar.
  • Question 2

When a substance, like salt, dissolves completely what is the name of the liquid that is produced?

CORRECT ANSWER
solution
EDDIE SAYS
A solution is made of a dissolved solid (like salt) split up into tiny particles and spread throughout the liquid - but remember that the salt (or whatever) is STILL A SOLID! A suspension is formed when a substance doesn't dissolve but floats around in the water, slowly settling to the bottom (like mud).
  • Question 3

Now that it is dissolved in the water, in what form is the salt?

CORRECT ANSWER
solid
EDDIE SAYS
It's hard to see it (pretty much impossible in actual fact!) but when a solid like salt dissolves in water it stays as a solid, only really, really small! You can prove it's still there as a solid by getting rid of the water (evaporating it) because the salt is revealed.
  • Question 4

Is it possible to get the substance (like salt) back out of the liquid?

CORRECT ANSWER
yes, you evaporate the liquid away
EDDIE SAYS
Imagine a pond with fish swimming around in it: what happens if the water evaporates away? The fish are left behind (they are solid(ish!)) and cannot evaporate. It's the same with solids like salt that dissolve - evaporate the liquid and they are left behind.
  • Question 5

When bicarbonate of soda is added to vinegar the two react together: the mixture fizzes and carbon dioxide gas is released.

 

Is it possible to reverse this reaction?

CORRECT ANSWER
no, new chemicals are formed so the reaction cannot be reversed
EDDIE SAYS
When a reaction happens, new chemicals are formed. In this case a gas is one of them and the carbon dioxide disappears off into the air. Even if you could get it back there's no way of returning to the original vinegar and bicarbonate of soda - it's IRREVERSIBLE.
  • Question 6

Which one of the following changes is NOT reversible?

CORRECT ANSWER
baking dough into bread
EDDIE SAYS
The molten lolly can be frozen into a solid again, the coffee can be recovered by evaporating the water but once dough is baked into bread it cannot be made back into dough by any process: it's irreversible.
  • Question 7

For the following questions join Emily who is mixing different substances with water and observing whether they dissolve or not or whether something else happens.

 

Emily begins by stirring a Vitamin C tablet into water. After a minute or so it disappears and when she filters it nothing is left in the filter paper.

 

What happened to the Vitamin C tablet?

CORRECT ANSWER
it dissolved in the water
EDDIE SAYS
Emily observed the disappearance of the tablet and when nothing was left in the filter paper it's clearly dissolved: the solid has separated into tiny particles of Vitamin C which easily fit through the holes in the paper.
  • Question 8

Next Emily tried some Plaster of Paris which looks like a white powder. When she stirred it into the water she noticed it going lumpy and the water became very warm. When she filtered the mixture she found white lumps in the filter paper and the liquid dripping through was colourless.

 

What happened to the Plaster of Paris?

CORRECT ANSWER
it reacted with the water to make a new substance
EDDIE SAYS
It might seem that as the white lumps are trapped the Plaster of Paris hasn't dissolved. In fact the clue is in the fact that the water became warm - a reaction has happened and so something new has been formed. Heat is often given out when reactions happen (like a hand-warmer where a fast reaction involving iron produces a lot of heat) and is a useful clue. Reactions always produce new substances.
  • Question 9

Next Emily asked her gran for one of the special tablets she used for cleaning her dentures (false teeth). Emily popped the tablet into some water: it fizzed and turned the water pink - it also smelled funny, sort of fruity and minty at the same time.

 

When she filtered the liquid there was nothing much left in the filter paper and a pink liquid dripped out.

 

What happened to the denture-cleaning tablet?

CORRECT ANSWER
it reacted with the water to make a new substance
EDDIE SAYS
It does seem to have dissolved as pink liquid passes out of the filter paper but the clue that a reaction has happened is in the fizzing: when a gas is released it shows that a new substance has been formed and the pink liquid will also be different to what was in the tablet.
  • Question 10

Emily went into her bedroom and got out her Chemistry set - she thought it would be fun to try adding some chemicals from there to the water. She checked the instruction booklet to make sure that none of them would be dangerous.

 

She decided to try a lovely blue crystal called COPPER SULPHATE. She stirred a spoonful into her water and observed that after a minute all the crystals had disappeared to leave a pretty blue liquid.

 

She filtered the blue liquid which passed through the filter paper leaving nothing behind.

 

What happened to the copper sulphate crystals?

CORRECT ANSWER
they dissolved in the water
EDDIE SAYS
The blue crystals dissolved to make a blue solution. The copper sulphate had split into tiny solid particles that fitted easily through the little holes in the filter paper.
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