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Non-reversible Changes

These questions help the student recognise when the changes we make to materials result in the formation of a new material and how to identify some common materials around us which are the products of non-reversible changes

'Non-reversible Changes' worksheet

Key stage:  KS 2

Curriculum topic:  Properties and Changes of Materials

Curriculum subtopic:  Non-reversible Changes

Difficulty level:  

down

Worksheet Overview

QUESTION 1 of 10

Melting and freezing are REVERSIBLE changes. This means that if we undo the change, we can get-back the materials we started with. A good example of this is ICE and WATER.

Remember that in Science, MATERIAL means any solid, liquid or gas that you can detect using your senses! Non-reversible changes result in a NEW and DIFFERENT material.

 

Birthday cake is a good example of a NEW MATERIAL. We mix together eggs, butter, flour and sugar, add heat and enjoy! BUT... we cannot reverse the changes. 'Cake' cannot be changed back into the ingredients we started with. (We would'nt want to anyway!)

Many non-reversible changes are caused by HEATING.

Gita and Jasa are carrying-out some science investigations. They are checking their understanding of REVERSIBLE reactions. 

Gita takes an ice lolly out of the freezer and leaves it on the kitchen table. Which change takes place?


freezing

evaporating

melting

condensing

Jasa uses an aerosol air freshner. He says, 'This reaction can be reversed.'


Is he correct?

yes

no

Gita breaks an egg into a bowl and whisks it with a fork.

 

Which of these best describes a beaten egg? 

solid

liquid

gas

Jasa cooks the egg. The heat changes the liquid egg into a...

gas

solid

pizza

In separate beakers, Gita mixes salt, sugar and coffee granules with water. They make clear liquids.

Help Gita choose the science word which describes this change.

dissolving

mixing

condensing

Gita and Jasa look in their fridge. They know that butter and yoghurt are made from milk. 

When milk is turned into new foods, we can describe the reaction as...

melting

reversible

non-reversible

tasty

The students know that heating some solids results in non-reversible reactions. Which THREE of these are made by non-reversible reactions?

melted chocolate

bread

yorkshire puddings

cup cakes

Gita thinks that they should extend their investigations to other materials around them.

They decide to have a bar-be-que. Yipee!

Mum has built a bar-be-que in the garden using bricks and concrete.


Bricks and concrete are examples of materials resulting from..?

reversible reactions

non-reversible reactions

Jasa puts the charcoal on the bar-be-que.


Charcoal is a material made by a non-reversible reaction. Which material is irreversibly changed to produce charcoal?

coal

clay

wood

Jasa and Gita enjoy eating the food cooked on their bar-be-que.


They think about what they have learnt. Can you help them remember the FOUR non-reversible ways of changing materials from this list?

dissolving

frying

baking

grilling

melting

burning

  • Question 1

Gita and Jasa are carrying-out some science investigations. They are checking their understanding of REVERSIBLE reactions. 

Gita takes an ice lolly out of the freezer and leaves it on the kitchen table. Which change takes place?


CORRECT ANSWER
melting
  • Question 2

Jasa uses an aerosol air freshner. He says, 'This reaction can be reversed.'


Is he correct?

CORRECT ANSWER
yes
EDDIE SAYS
The gas in the can evaporates. If Jasa could collect the gas and condense it, he would have the material he started with!
  • Question 3

Gita breaks an egg into a bowl and whisks it with a fork.

 

Which of these best describes a beaten egg? 

CORRECT ANSWER
liquid
EDDIE SAYS
OK! It's a bit gloopy, but beaten egg 'flows' and takes on the shape of its container. The gas Gita has beaten into it makes the surface bubbles.
  • Question 4

Jasa cooks the egg. The heat changes the liquid egg into a...

CORRECT ANSWER
solid
EDDIE SAYS
The heat has turned the egg into a new material. Jasa cannot change the egg back to liquid, raw egg.
  • Question 5

In separate beakers, Gita mixes salt, sugar and coffee granules with water. They make clear liquids.

Help Gita choose the science word which describes this change.

CORRECT ANSWER
dissolving
EDDIE SAYS
When the solid cannot be seen, making a clear (maybe coloured) liquid, the REVERSIBLE change is dissolving.
  • Question 6

Gita and Jasa look in their fridge. They know that butter and yoghurt are made from milk. 

When milk is turned into new foods, we can describe the reaction as...

CORRECT ANSWER
non-reversible
EDDIE SAYS
Milk cannot be separated from butter or yoghurt, because yoghurt and butter are the result of non-reversible reactions! Can you think of any other products made from non-reversible reactions starting with milk?
  • Question 7

The students know that heating some solids results in non-reversible reactions. Which THREE of these are made by non-reversible reactions?

CORRECT ANSWER
bread
yorkshire puddings
cup cakes
EDDIE SAYS
Heating changes materials. We use heat to cook mixtures of materials to make new, tasty foods.
  • Question 8

Gita thinks that they should extend their investigations to other materials around them.

They decide to have a bar-be-que. Yipee!

Mum has built a bar-be-que in the garden using bricks and concrete.


Bricks and concrete are examples of materials resulting from..?

CORRECT ANSWER
non-reversible reactions
EDDIE SAYS
Concrete is a mixture of sand, water and cement. The changes which take place in this mixture cannot be reversed. When clay is 'fired' to a very high temperature, it changes into brick, another non-reversible reaction!
  • Question 9

Jasa puts the charcoal on the bar-be-que.


Charcoal is a material made by a non-reversible reaction. Which material is irreversibly changed to produce charcoal?

CORRECT ANSWER
wood
EDDIE SAYS
Charcoal is made by heating wood to a high temperature, but not allowing it to catch fire!
  • Question 10

Jasa and Gita enjoy eating the food cooked on their bar-be-que.


They think about what they have learnt. Can you help them remember the FOUR non-reversible ways of changing materials from this list?

CORRECT ANSWER
frying
baking
grilling
burning
---- OR ----

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