Year 7 Science
7C1: The Particle Model
Home-Learning Challenge
Name: ________________________________________
Form: ___________
Task Sheet 1 (Bronze Challenge): The Particle Model
Use the words in the box to label the diagram below.
This particle diagram
shows the arrangement
of particles in a
………………………………..........
………………………….....
………………………….
This particle diagram
shows the arrangement
…………………………
of particles in a
.
………………………………..........
……………………….....
………………………....
This particle diagram
shows the arrangement
of particles in a
………………………………..........
freezing
melting
liquid
solid
condensing
evaporating
sublimation
gas
Complete the following sentences.
1. The particles in a solid are arranged ___________________ (in a pattern / randomly).
They are held close together by ________________ (strong / weak) forces of
attraction and can _____________ (move / vibrate).
2. The particles in a liquid are arranged ___________________ (in a pattern / randomly).
They are ___________________ (close together / far apart) and can _____________
(move / vibrate) over one another ______________ (quickly / slowly).
3. The particles in a gas are arranged ___________________ (in a pattern / randomly).
They are ___________________ (close together / far apart) and can _____________
(move / vibrate) ______________ (quickly / slowly).
4. Complete the table below.
Solid
Liquid
Gas
Example
Can the volume change?
Can the shape change?
Can it be compressed?
Is its density high or low?
5. Solids and liquids cannot be compressed (squashed) because the particles are _________
___________ (far apart / close together) so cannot get ________________________
(closer together / further apart).
6. Gases can be compressed (squashed) because the particles are ______________
______________ (far apart / close together) so can be pushed ________________
______________ (closer together / further apart).
Task Sheet 2 (Bronze Challenge): Diffusion
What happens to particles during diffusion?
…………………………………………………………………………………………………………………………………………………
………………………………………………………………………………………………………………………………………………..
The diagram below shows two gas jars. One is full of bromine gas, the other is full of air;
they are separated by a glass disc. When the glass is removed diffusion occurs.
Complete the second diagram to show how the particles would be arranged after diffusion.
Before diffusion
Key:
= particle of bromine
After diffusion
= particle of air
Task Sheet 3 (Bronze Challenge): Expansion and Contraction
Complete the following sentences.
When a solid, liquid or gas is heated it _________________ (expands / contracts) because
the particles move or vibrate ______________ (slower / faster) and ________________
___________ (spread out / get closer together).
When a solid, liquid or gas is cooled down it _________________ (expands / contracts)
because the particles move or vibrate _________________ (slower / faster) and
_______________________________ (spread out / get closer together).
The diagram below shows how particles are arranged in a solid that is cold. Draw another
diagram to show how the particles would be arranged if the solid was heated.
Diagram to show how the particles are arranged in a solid that is cold:
Diagram to show how the particles are arranged in a solid that is hot:
Task Sheet 4 (Bronze Challenge): The Story of Robert Brown
Robert Brown was a Scottish scientist who studied botany – the science of plants.
One day in 1827 he was using his microscope to look at some pollen grains that were floating
in water. To his surprise he noticed that the pollen grains were moving in a strange, zigzag
way. He checked his observations carefully and found that they were correct.
He knew that pollen came from living plants. At first he thought that the pollen itself might
be alive and capable of moving on its own. He tried the experiment again, but instead of
pollen he used something that he knew definitely couldn’t be alive. The zigzag motion was
still there! This really baffled Brown. He reported his results, but could not explain why the
pollen moved in this way. The experiment was then forgotten as no-one could come up with a
convincing explanation.
Nearly eighty years later in 1905 Albert Einstein came up with a theory to explain Brown’s
observations. He suggested that the pollen grains were being bombarded on all sides by
water particles. The water particles were too small to be seen. The effect of lots of the
water particles added together was just enough to push the pollen grains around.
In 1908 Jean-Baptiste Perrin used Einstein’s theory to calculate the size of a water particle
(molecule). This estimate suggested that water particles were less than 0.000 000 001
metres (10–9 m) in size.
We now call this movement of water molecules Brownian motion (after Robert Brown) and use
it to explain why diffusion occurs in liquids.
Task:
1. The pictures on the opposite page represent the story you have just read.
Put a number in each box to show what order they took place.
2. Which scientist first made the observations of the moving pollen grains?
…………………………………………………………………………………………………………………………………………………………………
3. Which scientist successfully explained the observation?
…………………………………………………………………………………………………………………………………………………………………
4. How many years were there between the observations and the conclusion?
…………………………………………………………………………………………………………………………………………………………………
5. What was Robert Brown’s first explanation for the movement of the pollen grains?
…………………………………………………………………………………………………………………………………………………………………
6. What non-living grains did Brown use to check his ideas?
…………………………………………………………………………………………………………………………………………………………………
Number =
Number =
Perhaps the pollen
grains stay alive after they
are taken off the plant –
maybe that’s why they can
move about.
Number =
I think that the
pollen grains that Mr Brown
observed are being moved
by invisible water
molecules.
Number =
1827
Look at this!
The soot is behaving just
like the pollen!
These pollen grains
are moving in a
remarkable way.
Number =
1908
1905
Number =
If Einstein’s
formula is correct,
water molecules are
smaller than a
billionth of a
metre.
This soot is definitely
not alive. I do not expect
that it will move like the
pollen grains.
Number =
Number =
So what do you
think makes the pollen
move Mr Brown?
I can see it now –
the little dots jiggling
about.
That’s right –
it’s called Brownian
motion, after Robert
Brown who first
discovered it.
I’ve no idea –
it’s a real mystery to
me!
Task Sheet 5 (Bronze Challenge): Revision Puzzle
a
b
c
d
e
f
g
h
1. Write your answers to the clues in the grid above.
a) Solids, liquids and gases all have different _______________________ .
b) Everything is made of tiny pieces called _______________________ .
c) Particles in a liquid or a gas can _______________________ around.
d) A _______________________ has particles that are a long way apart.
e) Smells spread through the air by _______________________ .
f) If you pump all the air out of a space, you have a _______________________ .
g) Particles in a solid cannot move around, they can only _______________________ .
h) Solids and liquids both have fixed _______________________ .
2. Write down the word in the shaded boxes.
___________________________________________________________________
Now write your own clue for this word.
___________________________________________________________________
___________________________________________________________________
Task Sheet 6 (Silver Challenge): Which substances expand the most?
Bar chart to show how much a 100m length of material expands when heated by 10°C
Expansion / mm
20
18
16
14
12
10
8
6
4
2
0
brass
iron
steel
platinum
alloy
concrete
ordinary
glass
oven glass
Material
1. Which material expands the most? ………………………………………………………
2. Which material expands the least? ………………………………………………………
3. When answering the next two questions remember to use the PEE (Point Evidence Explain)
structure. The evidence should be data from the bar chart.
a) Why is oven glass more useful for making dishes to go in the oven and oven windows
than normal glass?
……………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………………
b) Explain why using steel reinforcing rods in concrete would cause fewer problems than
using brass rods during hot weather.
……………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………………
Task Sheet 7 (Silver Challenge): Using the Particle Model
Choose one of the following examples.
In the space on the next page:
1. Describe what is happening in your example.
2. Draw a particle diagram to help you to explain why this is happening.
3. Explain what is happening in your example using ideas about particles.
Bike tyres
Swimming pool
Liz has a mountain bike. She fills her
tyres with air. The tyres give a
smooth ride because the change
shape around small bumps on the road.
She tries a new, solid rubber tyre.
She finds it very uncomfortable over
bumpy ground.
Joe and Eve run to the swimming pool.
They then have races by running
through the water. However hard
they try, they run much slower
through the water
than through the air.
Water bed
Jack has a water bed. The bed has a big plastic bag filled with water instead
of a mattress. He says it is really comfortable because it fits around the
shape of his body when he lies down.
What is happening in your example?
……………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………………
Diagram:
Explanation:
……………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………………
Task Sheet 8 (Gold Challenge): How does adding salt to water affect the melting point?
1. What does the term melting point mean?
………………………………………………………………………………………………………………………
………………………………………………………………………………………………………………………
2. The table below shows how the melting point of a solution changes when the concentration
of salt is changed.
Concentration of Salt / %
Melting Point of Solution / °C
0
0
1
-1
2
-2
3
-3
4
-4
5
-5
6
-6
Draw a line graph of melting point of solution (y-axis) against concentration of salt (xaxis). Be careful, the melting points go from 0°C down to -6°C, so the y-axis needs to be
drawn below the x-axis rather than above it.
Draw your graph on the graph paper on the opposite page using a pencil and ruler.
Remember to label each axis with a quantity and a unit and draw a line of best fit through
the points.
3. Describe the trend (pattern) shown on your graph.
………………………………………………………………………………………………………………………...
……………………………………………………………………………………………………………………...…
…………………………………………………………………………………………………………………...……
4. What is the melting point of pure water? ………………………………………………………….……
5. What melting point would a 3.5% salt solution have? …………………………………………..….…
6. Estimate the melting point of an 8% salt solution. ………………………………………………..……
7. Sea water has an average melting point of -2.4°C. What concentration of salt must it
have? ………………………………………………………………………………………………………….……
8. The Dead Sea has a salt concentration of 29%. Assuming the trend in melting points
continues after a 6% concentration of salt, what would the melting point be? ……………..…
Task Sheet 9 (Gold Challenge): Air Pressure
Read the article below carefully then answer the questions. You might like to
highlight key words while you are reading through.
Air pressure exceeds 16 horsepower!
In 1656 Otto von Guericke arranged a
fantastic demonstration in a town
called Magdeburg.
He pushed
together two large metal hemispheres
to make a giant ball. The only thing
holding them together was a layer of
grease and they could easily slide
apart.
Next, using a modified pump, he
removed the air from the two joined
hemispheres. Now a person could not
pull them apart. In fact, Otto von
Guericke ordered that a team of eight
horses be hitched to each hemisphere.
They still couldn’t pull them apart!
For centuries, scientists had debated
whether it was possible to create a
vacuum – a space that contained no
particles.
Many thought it was
impossible and the phrase ‘nature
abhors a vacuum’ described their
belief. Otto von Guericke showed with
his experiment that a vacuum could
exist and that the pressure of air
particles on the outside of the
hemispheres was a very powerful
force.
Questions:
1. What is a ‘hemisphere’?
……………………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………………..
2. Add some air particles to the diagrams below to show how the particles would
have been arranged BEFORE and AFTER the air was pumped out of the
hemispheres.
BEFORE
AFTER
3. How would the air pressure inside the hemispheres and outside the
hemispheres compare BEFORE the air was pumped out of them?
……………………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………………..
4. How would the air pressure inside the hemispheres and outside the
hemispheres compare AFTER the air was pumped out of them?
……………………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………………..
5. Why was it so difficult to pull the hemispheres apart? What was keeping
them together?
……………………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………………..
…………………………………………………………………………………………………………………………………………..
6. What is a vacuum?
……………………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………………..
7. Before Otto von Guericke’s demonstration some scientists believed that it
was impossible to create a vacuum. Why is it difficult to create a vacuum?
……………………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………………..
8. There was a saying ‘nature abhors a vacuum’. What does the word ‘abhors’
mean?
……………………………………………………………………………………………………………………………………………
9. Do some research on Otto von Guericke. Who was he? What else did he
discover or invent?
……………………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………………..
……………………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………………..
…………………………………………………………………………………………………………………………………………..
…………………………………………………………………………………………………………………………………………..
Key Words Glossary
The Particle Model:
particle
states of matter
solid
liquid
gas
arrangement
forces of attraction
vibrate
property
flow
volume
density
compress
Physical Changes:
change of state
melting
freezing
boiling
condensing
subliming
melting point
boiling point
energy
diffusion
gas pressure
expand
contract