Aseel Samaro

Making sense of models

A model is a way of representing something that cannot be seen.

Particles are too small to be seen – so the particle model is a useful tool, allowing us to understand the properties and observations of solids, liquids and gases.

However, it does not provide us with the full picture.

Introduction

You already know about atoms, elements and compounds.

All matter is made from atoms.

More advanced models are used to represent elements and compounds, compared with the model used to represent solids, liquids and gases.

This is because the simplified particle model is ‘good enough’ for the purposes of explaining states of matter and changes of state.

A good enough model

Popcorn popping is a model of a change of state.

What Makes Popcorn Pop? EC

List all the properties of solids, liquids and gases that the standard particle model can explain, making it a ‘good enough’ model.

Liquids and gases can flow but solids cannotsolids have a fixed shape

solids are stronger than liquids and gases.

Each element is made of only one type of atom.

Compounds are made of two or more elements chemically bonded together.

Developing models further

This figure shows the structures of two different solid compounds – aluminium oxide (Al2O3) and magnesium oxide (MgO).

These adapted models can now explain more than just the state of matter a material is in.

As you can see from the diagrams, both are solids but the atoms are organised in different ways.

Look at the model of carbon dioxide gas and helium gas in this figure.

By adapting the model to show the relative sizes of the atoms, you can see why carbon dioxide is much heavier than helium.

Draw a model to show liquid water (H2O) and liquid hydrochloric acid (HCl).

What does this model show that the standard particle model cannot?

This figure shows diagrams of water in the solid, liquid and gaseous states.

Evaluating models

You need to be clear, when using models, about what they can explain and what their limitations are.

John Dalton was the first person to propose a model for particles.

Today, scientists are still adapting and changing their ideas about particles as they learn more.

Did you know…?

Thank you