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Mixing Substances 2

This worksheet offers the student a variety of scenarios in which substances are mixed together, asking them the effects of such mixing and whether the change is permanent or not.

'Mixing Substances 2' 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

 Barney and Tim are finding out what happens when certain substances are mixed together. They are interested in OBSERVING any changes and trying to find out whether the change is permanent ( IRREVERSIBLE) or temporary (REVERSIBLE).

 

 

 

They start by drawing up a chart to write their results in:

 

 

NAME MIXED WITH RESULT CHANGE?
sand water did not dissolve reversible
salt water   reversible
sugar water dissolved - clear  
instant coffee water dissolved - brown irreversible
Andrews salts water fizzed - gas produced irreversible
bicarb of soda water did not dissolve reversible
bicarb of soda vinegar fizzed - gas produced irreversible
boiled sweet water dissolved - pink reversible
dirty 2p coin lemon juice coin clean/juice dirty irreversible

 

 

Barney and Tim found that when sand or bicarbonate of soda were stirred into water they did not dissolve. They said this was reversible, which means that they could separate the solids from the water.

 

 

How would they do this?

 

Sieve it

Filter it

Boil it

They said that instant coffee, boiled sweet and sugar all dissolved in water. What do we call the liquid made when solids dissolve?

 

Solution

Mixture

Suspension

Barney and Tim did not fill in the result for what happened when salt is mixed with water:

 

NAME MIXED WITH RESULT CHANGE?
salt water   reversible

 

 

What do you think they should have written?

Did not dissolve

Dissolved - white

Dissolved - clear

When they added sugar to water Barney and Tim should have filled in the 'Change?' column. What should they have put?

 

NAME MIXED WITH RESULT CHANGE?
sugar water dissolved - clear  

 

Reversible

Irreversible

Barney and Tim said that the salt, instant coffee and boiled sweet could all be retrieved from the water (in other words it's reversible). How could they do this?

Filter it

Evaporate the water

Heat it up

When they tried that method with the liquid they were left with from the boiled sweet, what would be left behind?

Boiled sweet

Sugar

Sticky mess

In the 'Change?' column they have filled in the answer for one of the substances incorrectly - which one?

 

NAME MIXED WITH RESULT CHANGE?
sand water did not dissolve reversible
salt water   reversible
sugar water dissolved - clear  
instant coffee water dissolved - brown irreversible
Andrews salts water fizzed - gas produced irreversible
bicarb of soda water did not dissolve reversible
bicarb of soda vinegar fizzed - gas produced irreversible
boiled sweet water dissolved - pink reversible
dirty 2p coin lemon juice coin clean/juice dirty irreversible

 

Sand

Instant coffee

Andrews salts

Boiled sweet

Two of the substances released gases when mixed with certain liquids - which solids were these?

 

NAME MIXED WITH RESULT CHANGE?
sand water did not dissolve reversible
salt water   reversible
sugar water dissolved - clear  
instant coffee water dissolved - brown irreversible
Andrews salts water fizzed - gas produced irreversible
bicarb. of soda water did not dissolve reversible
bicarb. of soda vinegar fizzed - gas produced irreversible
boiled sweet water dissolved - pink reversible
dirty 2p coin lemon juice coin clean/juice dirty irreversible

 

Bicarbonate of soda

Dirty 2p coin

Andrews salts

Sand

When vinegar and bicarbonate of soda are added together an exciting fizzing reaction takes place - it's often used in pretend volcanos. The gas given off in this reaction is carbon dioxide. Why do you think that this change cannot be reversed?

 

 

Changes involving chemicals can never be reversed

Once released, the carbon dioxide cannot be recaptured

Once released, the carbon dioxide cannot be put back to form the original chemicals

The dirty 2p coin was cleaned by the lemon juice. If the coin is used as normal again it will become dirty once more. Why do you think Tim and Barney said that this change is irreversible?

They're wrong - the coin is permanently cleaned

They're right - the coin will react with other chemicals and change once more

They're wrong - the lemon juice gives the coin a protective coating

  • Question 1

Barney and Tim found that when sand or bicarbonate of soda were stirred into water they did not dissolve. They said this was reversible, which means that they could separate the solids from the water.

 

 

How would they do this?

 

CORRECT ANSWER
Filter it
EDDIE SAYS
A sieve's holes are too big to stop the sand or bicarbonate of soda from getting through so the tiny holes of a filter would be needed to trap the particles.
  • Question 2

They said that instant coffee, boiled sweet and sugar all dissolved in water. What do we call the liquid made when solids dissolve?

 

CORRECT ANSWER
Solution
EDDIE SAYS
The solution to this question is .... solution! So, salt + water = salt solution.
  • Question 3

Barney and Tim did not fill in the result for what happened when salt is mixed with water:

 

NAME MIXED WITH RESULT CHANGE?
salt water   reversible

 

 

What do you think they should have written?

CORRECT ANSWER
Dissolved - clear
EDDIE SAYS
When the white crystal, salt, dissolves in water it splits up into tiny salt particles you cannot see and the result looks like water - clear (or, better still, 'colourless', but Barney and Tim probably don't know that word!).
  • Question 4

When they added sugar to water Barney and Tim should have filled in the 'Change?' column. What should they have put?

 

NAME MIXED WITH RESULT CHANGE?
sugar water dissolved - clear  

 

CORRECT ANSWER
Reversible
EDDIE SAYS
Although the sugar seems to have disappeared it IS still there, but in tiny sugar particles; evaporate the water away carefully and they'll be revealed. Do it too hot and fast and all you'll get is a brown sticky mess of caramel!
  • Question 5

Barney and Tim said that the salt, instant coffee and boiled sweet could all be retrieved from the water (in other words it's reversible). How could they do this?

CORRECT ANSWER
Evaporate the water
EDDIE SAYS
All solutions are a liquid (usually water) with a solid in tiny particles spread around in it. If you gently evaporate the water away, the solid will be left behind (just like the fish in a pond in Africa as the water level goes down).
  • Question 6

When they tried that method with the liquid they were left with from the boiled sweet, what would be left behind?

CORRECT ANSWER
Sticky mess
EDDIE SAYS
They certainly won't get the sweet back as it was, so a sticky mess of sugar and colourings will be left in the dish - fancy licking it out?!
  • Question 7

In the 'Change?' column they have filled in the answer for one of the substances incorrectly - which one?

 

NAME MIXED WITH RESULT CHANGE?
sand water did not dissolve reversible
salt water   reversible
sugar water dissolved - clear  
instant coffee water dissolved - brown irreversible
Andrews salts water fizzed - gas produced irreversible
bicarb of soda water did not dissolve reversible
bicarb of soda vinegar fizzed - gas produced irreversible
boiled sweet water dissolved - pink reversible
dirty 2p coin lemon juice coin clean/juice dirty irreversible

 

CORRECT ANSWER
Instant coffee
EDDIE SAYS
When coffee dissolves in water it is now in the form of tiny particles of coffee - evaporate the water away gently and you should see the coffee again, so it is reversible, not as Barney and Tim said, irreversible.
  • Question 8

Two of the substances released gases when mixed with certain liquids - which solids were these?

 

NAME MIXED WITH RESULT CHANGE?
sand water did not dissolve reversible
salt water   reversible
sugar water dissolved - clear  
instant coffee water dissolved - brown irreversible
Andrews salts water fizzed - gas produced irreversible
bicarb. of soda water did not dissolve reversible
bicarb. of soda vinegar fizzed - gas produced irreversible
boiled sweet water dissolved - pink reversible
dirty 2p coin lemon juice coin clean/juice dirty irreversible

 

CORRECT ANSWER
Bicarbonate of soda
Andrews salts
EDDIE SAYS
From Barney and Tim's chart you can see that bicarbonate of soda fizzed in vinegar while Andrews salts fizzed in water, both releasing carbon dioxide gas.
  • Question 9

When vinegar and bicarbonate of soda are added together an exciting fizzing reaction takes place - it's often used in pretend volcanos. The gas given off in this reaction is carbon dioxide. Why do you think that this change cannot be reversed?

 

 

CORRECT ANSWER
Once released, the carbon dioxide cannot be put back to form the original chemicals
EDDIE SAYS
When two things react and release a gas that's going to be a permanent (irreversible) change: you cannot collect that gas and somehow add it back into what's left and expect it to magically return to its original state!
  • Question 10

The dirty 2p coin was cleaned by the lemon juice. If the coin is used as normal again it will become dirty once more. Why do you think Tim and Barney said that this change is irreversible?

CORRECT ANSWER
They're right - the coin will react with other chemicals and change once more
EDDIE SAYS
The reaction between the coin and the lemon juice produced new chemicals (which is why the lemon juice is dirty - they're in there) and so this is a permanent (irreversible) change. However, through normal use the surface of the coin will react again and become 'dirty'.
---- OR ----

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