# Testing Gases

In this worksheet, students will test their understanding of the material properties of gases and how, in science, we classify a material as a gas.

Key stage:  KS 2

Curriculum topic:   States of Matter

Curriculum subtopic:   Solids, Liquids and Gases

Difficulty level:

### QUESTION 1 of 10

Imagine that you have discovered a new material. You need to share your discovery with other scientists all around the world. What tests can you carry out to classify your new material as a solid, liquid or gas? Just what makes a gas, a gas?

Hmmm - that's a tricky question.  Let's see whether we can find some answers.

Just what makes a gas, a gas?  They all have certain properties (features) that make them gases.

All gases have two of these properties.  Which two do you think they are?

colourless (has no colour)

easy to compress (squash)

have a definite volume (take up a set space)

can spread to fill a container

poisonous

Fred says: If I fill a syringe with gas, put my finger over the end and push hard on the plunger, I can squash the gas into a smaller space

Which statement explains this scientifically?

Fred is extremely strong

gases can be easily compressed

the gas has escaped into the air

Julie sprays an aerosol air freshener in one corner of the classroom. After a few minutes, Fred can smell it in the corridor outside the room.

What does this tell us about gases?

all gases have an odour

there is a draft in the classroom blowing the gas about

gases move to fill the space available

There are four statements below, only two of which are true for gases.

Which TWO of these statements do you think help us to classify a material as a gas?

(By the way, the word COLOURLESS is the way that scientists describe something that has no colour, like the glass in a window.  You might say "clear" or "see-through", but colourless is the proper scientific word.  Delicious!).

gases cannot be cut

gases do not have a definite volume

gases can melt

gases are always colourless

Is the following statement true or false?

Gases can flow.

True

False

Complete the following statement:

If a gas is cooled enough, it changes into a __________.

Right, so time to do some real thinking here.  Why has the gas turned into a liquid?  Fred and Julie disagree on the reason.  Let's see what they say.

Fred explains this change from gas to liquid by saying:

"The gas particles (that's atoms/molecules) have less energy so they slow down."

Julie says: "The volume (or space) occupied by the gas is reduced (that means it's smaller) because the gas particles have less space between them."

What do you think? Choose one of the following options:

Fred is correct

Julie is correct

They are both correct

What is the name of the gas produced when water is heated to its boiling point?

With adult help, Julie and Fred boil a pan of water to observe what happens. They notice that bubbles form in the liquid and rise to the surface. The more the water is heated, the more bubbles form.

What is the gas in these bubbles? Choose ONE of the following options:

air

oxygen

carbon dioxide

steam

Do you know at what temperature, in degrees Celsius, does water boil and change into steam?

230

37

100

0

• Question 1

Just what makes a gas, a gas?  They all have certain properties (features) that make them gases.

All gases have two of these properties.  Which two do you think they are?

easy to compress (squash)
can spread to fill a container
EDDIE SAYS
Well, in fact many gases are colourless and poisonous but all gases are easy to compress (squash) and can spread to fill a container. If you have a bike pump try putting your thumb over the opening and then pushing the plunger down. You should be able to get it quite a way before it becomes difficult. You\'ve compressed air! Also try a quick squirt of an air freshener into a corner of the room (assuming no one\'s going to object). How soon before you can smell that all over the room? Gases spread out to completely fill the space.
• Question 2

Fred says: If I fill a syringe with gas, put my finger over the end and push hard on the plunger, I can squash the gas into a smaller space

Which statement explains this scientifically?

gases can be easily compressed
EDDIE SAYS
Because the particles in a gas are far apart, gases can be compressed, reducing the amount of space they take up. That means even a lad like Fred can squash the gas into a smaller space in the syringe.
• Question 3

Julie sprays an aerosol air freshener in one corner of the classroom. After a few minutes, Fred can smell it in the corridor outside the room.

What does this tell us about gases?

gases move to fill the space available
EDDIE SAYS
The air freshener is made of nice smelling gases and, in fact, gas particles travel all over the room and so that means the volume of the gas is never constant. That little squirt of air freshener has spread out to fill the entire space.
• Question 4

There are four statements below, only two of which are true for gases.

Which TWO of these statements do you think help us to classify a material as a gas?

(By the way, the word COLOURLESS is the way that scientists describe something that has no colour, like the glass in a window.  You might say "clear" or "see-through", but colourless is the proper scientific word.  Delicious!).

gases cannot be cut
gases do not have a definite volume
EDDIE SAYS
Air is a colourless gas, so it\'s tempting to think of all gases as colourless. In fact, some gases do have a colour, for example, chlorine is a yellow green colour. Chlorine is used in disinfectants to kill micro-organisms. It\'s very smelly too! As we\'ve seen, gases spread out to completely fill their containers and, of course you can\'t cut them (even if the exciting book you\'re reading says, \"...you could have cut the atmosphere with a knife.\" That\'s just the author\'s imaginative expression!)
• Question 5

Is the following statement true or false?

Gases can flow.

True
EDDIE SAYS
Gases can flow, but slowly because they are light. Gases which are heavier than air can be shown to flow: carbon dioxide, made by mixing vinegar with baking powder, can be \'poured\' onto a candle flame to put it out! Isn\'t science wonderful?
• Question 6

Complete the following statement:

If a gas is cooled enough, it changes into a __________.

liquid
EDDIE SAYS
OK, so think of your bathroom just after you\'ve had a bath or shower. Can you see yourself in the mirror? No, because it\'s \"all steamed up\". In fact, the steam in the room has touched the cold mirror and CONDENSED into a liquid - the gas has cooled down into a liquid.
• Question 7

Right, so time to do some real thinking here.  Why has the gas turned into a liquid?  Fred and Julie disagree on the reason.  Let's see what they say.

Fred explains this change from gas to liquid by saying:

"The gas particles (that's atoms/molecules) have less energy so they slow down."

Julie says: "The volume (or space) occupied by the gas is reduced (that means it's smaller) because the gas particles have less space between them."

What do you think? Choose one of the following options:

They are both correct
EDDIE SAYS
Well, surprisingly, they\'re both correct! As the gas particles lose energy (as they get cooler) and cool, there is less space between them (so, they\'re closer together) and they condense into a liquid. Needs thinking about, though, doesn\'t it?
• Question 8

What is the name of the gas produced when water is heated to its boiling point?

steam
water vapour
EDDIE SAYS
Think of a saucepan bubbling on the cooker: that\'s water turning to steam or, more scientifically, water vapour. Liquid turning to gas as it gets hotter and hotter.
• Question 9

With adult help, Julie and Fred boil a pan of water to observe what happens. They notice that bubbles form in the liquid and rise to the surface. The more the water is heated, the more bubbles form.

What is the gas in these bubbles? Choose ONE of the following options:

steam
EDDIE SAYS
The water nearer the source of the heat changes into steam first and forms gas bubbles - bubbles of steam - within the liquid. They rise to the surface and burst to allow the steam to escape into the air.
• Question 10

Do you know at what temperature, in degrees Celsius, does water boil and change into steam?

100
EDDIE SAYS
Yes, it\'s 100C - the boiling point of water. In fact, 37 degrees Celsius (°C) is about your body temperature! Water freezes at zero degrees into ice.
---- OR ----

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