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Dissolving

In this worksheet, students will be helped to extend their understanding of what dissolving is about and what happens when substances form solutions.

'Dissolving' worksheet

Key stage:  KS 2

Curriculum topic:  Properties and Changes of Materials

Curriculum subtopic:  Dissolving and Solutions

Difficulty level:  

down

Worksheet Overview

QUESTION 1 of 10

 In this worksheet you will have the opportunity to look at different aspects of dissolving: what happens to a solid when it dissolves?

 

Where does it go?

 

What happens if you try to separate it?

 

Can you separate it?

 

What happens if you heat it?

 

Tablet dissolving

 

See whether you can follow these arguments through logically as you work through the questions.

Ian has been trying out two different liquids to see whether certain substances will dissolve in them: the liquids are WATER and COOKING OIL.

Here is a chart of his results:

NAME OF SUBSTANCE DISSOLVES IN WATER? DISSOLVES IN OIL?
X Yes No
Y No No
Z No Yes

 

Which substance - X, Y or Z - is salt?

X

Y

Z

You chose this one because......

salt is soluble in water but insoluble in oil

salt is soluble in oil but insoluble in water

salt is insoluble in both oil and water

salt is soluble in both oil and water

Here is the chart of Ian's results:

NAME OF SUBSTANCE DISSOLVES IN WATER? DISSOLVES IN OIL?
X Yes No
Y No No
Z No Yes

 

Here's what Ian wrote in his book: "I found that if a substance would not dissolve in water then it would dissolve in oil."

Do you agree with him?

Yes because Z didn't dissolve in water but did in oil

No because Y didn't dissolve in either water or oil

No because X won't dissolve in oil

Harry and Ben were having an argument about orange juice.  Harry said that it was mainly water while Ben said it couldn't be as it was an orange colour.  Harry said he'd prove it!

 

First he poured some orange juice into a dish and heated it gently over a flame:

 

 Orange juice

 

After a few minutes they saw a gas rising up from the hot orange juice.

 

Predict what Harry and Ben saw coming out of the dish.

 

Evaporation apparatus

smoke

steam

orange vapour

Ben still wasn't convinced that orange juice is mainly water so Harry said that he'd try to separate the orange bits by filtering:

 

 Filtration

 

He poured orange juice into the filter and allowed the liquid to drip through.

 

What do you think Harry and Ben saw was left in the filter paper?

bits of orange

bits of sugar

nothing

What do you think Harry and Ben saw dripping out of the filter paper?

water

orange juice

sugar solution

Ben still said that these experiments didn't prove that orange juice was mainly water, so Harry tried heating it again.

 

He set up this apparatus:

 

 Boiling apparatus

 

Next Harry, wearing gloves, carefully placed a cold surface against the gas coming out of the flask and droplets appeared on it.

 

What colour do you think the droplets were?

 

 Water droplets

orange

colourless

white

What is the name of the process that Harry used to collect some of the liquid formed from the gas given off by the orange juice?

evaporation

condensation

solidification

Harry and Ben collected some of the droplets from the cold surface. They tasted them carefully - what do you think they tasted of?

nothing

orange

sugar

If Harry allowed the rest of the liquid in his orange juice to evaporate slowly away, what do you predict would be left behind?

nothing

orange solid

salt

  • Question 1

Ian has been trying out two different liquids to see whether certain substances will dissolve in them: the liquids are WATER and COOKING OIL.

Here is a chart of his results:

NAME OF SUBSTANCE DISSOLVES IN WATER? DISSOLVES IN OIL?
X Yes No
Y No No
Z No Yes

 

Which substance - X, Y or Z - is salt?

CORRECT ANSWER
X
EDDIE SAYS
It's X as salt dissolves in water but not oil. More in Q2.
  • Question 2

You chose this one because......

CORRECT ANSWER
salt is soluble in water but insoluble in oil
EDDIE SAYS
So, salt is soluble in water so it dissolves in water. It is insoluble in oil so it does not dissolve in oil.
  • Question 3

Here is the chart of Ian's results:

NAME OF SUBSTANCE DISSOLVES IN WATER? DISSOLVES IN OIL?
X Yes No
Y No No
Z No Yes

 

Here's what Ian wrote in his book: "I found that if a substance would not dissolve in water then it would dissolve in oil."

Do you agree with him?

CORRECT ANSWER
No because Y didn't dissolve in either water or oil
EDDIE SAYS
Ian said that if a substance wouldn't dissolve in water (Y&Z for him) then it would dissolve in oil, but Y won't dissolve in water or oil so that conclusion cannot be correct.
  • Question 4

Harry and Ben were having an argument about orange juice.  Harry said that it was mainly water while Ben said it couldn't be as it was an orange colour.  Harry said he'd prove it!

 

First he poured some orange juice into a dish and heated it gently over a flame:

 

 Orange juice

 

After a few minutes they saw a gas rising up from the hot orange juice.

 

Predict what Harry and Ben saw coming out of the dish.

 

Evaporation apparatus

CORRECT ANSWER
steam
EDDIE SAYS
The vapour Harry and Ben would have seen would have no colour: the orange colour in orange juice is caused by solids dissolved in the mixture and they cannot evaporate (because they're solid!). So, just steam or water vapour.
  • Question 5

Ben still wasn't convinced that orange juice is mainly water so Harry said that he'd try to separate the orange bits by filtering:

 

 Filtration

 

He poured orange juice into the filter and allowed the liquid to drip through.

 

What do you think Harry and Ben saw was left in the filter paper?

CORRECT ANSWER
bits of orange
EDDIE SAYS
If it was pure orange juice Harry and Ben would see little pieces of orange left in the filter paper. They are too big to pass through the tiny holes in the paper with the rest of the juice and get trapped.
  • Question 6

What do you think Harry and Ben saw dripping out of the filter paper?

CORRECT ANSWER
orange juice
EDDIE SAYS
When substances dissolve they separate into tiny, tiny particles, small enough to pass through the little holes in the filter paper. Big bits of orange will get trapped but the dissolved orange solids and sugar pass through.
  • Question 7

Ben still said that these experiments didn't prove that orange juice was mainly water, so Harry tried heating it again.

 

He set up this apparatus:

 

 Boiling apparatus

 

Next Harry, wearing gloves, carefully placed a cold surface against the gas coming out of the flask and droplets appeared on it.

 

What colour do you think the droplets were?

 

 Water droplets

CORRECT ANSWER
colourless
EDDIE SAYS
When you heat a solution only the water can evaporate away because, although the dissolved solids in the orange juice (like sugar) are really small, THEY ARE STILL SOLID and cannot evaporate away. So the vapour would have no colour - that's colourless!
  • Question 8

What is the name of the process that Harry used to collect some of the liquid formed from the gas given off by the orange juice?

CORRECT ANSWER
condensation
EDDIE SAYS
Condensation is formed from condensation! What that means is that the droplets of water (condensation) are the result of CONDENSING steam into water, taking away its heat energy so it cools down from being a gas to being a liquid.
  • Question 9

Harry and Ben collected some of the droplets from the cold surface. They tasted them carefully - what do you think they tasted of?

CORRECT ANSWER
nothing
EDDIE SAYS
Since the liquid condensed from the steam cannot contain any dissolved solids it's going to be water which doesn't really taste of anything much.
  • Question 10

If Harry allowed the rest of the liquid in his orange juice to evaporate slowly away, what do you predict would be left behind?

CORRECT ANSWER
orange solid
EDDIE SAYS
Since orange juice is a solution of water with sugar and natural orange solids in it, that is what would be left behind once all the water has evaporated away.
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