Predicting states of matter and limitations of the particle model | Chemistry

Starter quiz

Which of the following statements can correctly finish this sentence? Substances in a solid state ...

cannot be compressed. ✓

do not take the shape of the container they are in. ✓

have larger particles than all substances in a liquid state.

have particles which have no energy at all.

have particles that vibrate around their fixed positions. ✓
Which of the following statements can correctly finish this sentence? Substances in a liquid state …

at their boiling point can form bubbles of the substance anywhere in the liquid. ✓

cannot be compressed. ✓

have particles at the surface which may have enough energy to escape. ✓

have particles that cannot move around and over each other.

take the shape of the bottom of the container they are in. ✓
Which of the following statements can correctly finish this sentence? Substances in a gas state …

are formed in the bubbles inside a liquid at boiling point. ✓

can be compressed. ✓

have particles that are not attracted to each other at all, ever.

have particles that can escape an open container to fill all the space. ✓

take the shape of the whole of the container they are in. ✓
As particles gain energy, they are able to overcome the ______ between them.

'forces of attraction' ✓
Which aspects of a particle change when a substance’s state of matter changes?

arrangement relative to other particles ✓

energy of particle ✓

movement of particle ✓

shape of particle

size of particle
Match the following terms to their definitions.

boiling point

⇔

temperature where substance changes from liquid state to gas state ✓

condensing point

⇔

temperature where substance changes from gas state to liquid state ✓

freezing point

⇔

temperature where substance changes from liquid state to solid state ✓

melting point

⇔

temperature where substance changes from solid state to liquid state ✓

Exit quiz

In the main image, the important information has been replaced with grey boxes. Which of the three answer images is an accurate representation of a chemical change of substances in the same state?
Sort the following states and the temperatures at which changes of state occur into the correct order, starting with a substance in the gas state.

1

⇔

substance in the gas state

2

⇔

condensing point

3

⇔

substance in the liquid state

4

⇔

freezing point

5

⇔

substance in the solid state
At which temperature are all of the following substances in a liquid state?

at -200 $^o$ C

at 25 $^o$ C

at 1500 $^o$ C

between 0 and 100 $^o$ C

never ✓
Three balloons are filled with neon, methane and oxygen, respectively (see image). Why would you expect the substance in the middle balloon to have the highest boiling point?

it has more than one type of atom in its molecules

it has strong covalent bonds in the molecules

it has stronger intermolecular forces between the particles ✓

it has the biggest particles and they do not move
Which of the following statements are correct?

ionic substances have weak electrostatic forces of attraction

metallic bonds are the attraction between metal ions and delocalised electrons ✓

particles are shown as solid spheres but are mainly empty space ✓

small covalent substances have weak forces of attraction between molecules ✓

the particle model does not show the movement or elasticity of particles ✓
The image shows the sublimation of carbon dioxide. What are some of the limitations of this representation?

the model does not show attraction between particles which affects state change ✓

the model does not show bonds or forces ✓

the model shows metallic bonding incorrectly

the particles are all shown as having the same size ✓

the particles are shown as inelastic spheres ✓

Worksheet

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Lesson Details

Key learning points

There are changes in arrangement, movement and energy of particles during state changes.
There are two types of change; physical and chemical, and the physical state of a substance can be predicted.
The attraction between particles has a role in determining the amount of energy needed for state changes.
The particle model has limitations, for example by showing particles as same sized, inelastic spheres.
The model does not show the attraction between the particles which affects the amount of energy needed to change state.

Common misconception

Pupils often confuse physical and chemical changes and think that all particles look and act like those shown in the particle model.

Give the pupils an array of different examples of physical and chemical reactions and get the pupils to consider if new substances have been produced. Show the pupils, using molymods, how different molecules can be.

Keywords

Physical change - A change in which no new substances are formed, such as a change in state, e.g. melting.
Chemical change - Occurs when a reaction takes place and atoms or ions in the reactants are rearranged to make new products/substances.
Particle model - A model that helps us to understand physical properties of substances. It uses circles or spheres to represent particles, i.e. atoms or compounds.
Limitation of a model - A point at which we cannot use the model to help us explain a scientific phenomena.