The Science of Matter
The Particle Model
Understanding solids, liquids, and gases
What is the Particle Model?
The particle model explains how matter behaves by describing all substances as being made of tiny particles. These particles are always moving and the way they are arranged determines whether something is a solid, liquid, or gas.
Particle Simulator
Solid
- • Arrangement: Particles are packed tightly in a regular pattern.
- • Movement: Particles vibrate in fixed positions - they cannot move around.
- • Properties: Fixed shape, fixed volume, cannot be compressed.
Changes of State
Heating gives particles more energy to move. Cooling removes energy so particles slow down.
Diffusion
Diffusion is the spreading out of particles from an area of higher concentration to an area of lower concentration.
Example: Perfume
When perfume is sprayed in one corner of a room, the particles spread throughout the room. You can smell it everywhere after a few minutes.
Factors Affecting Diffusion
Higher temperature = faster diffusion (particles have more energy). Gases diffuse faster than liquids (particles are more spread out).
Hazards & Safety
Working safely in the laboratory
Hazard Symbols
Learn to recognise these important safety symbols used in laboratories:
Flammable
Catches fire easily
Corrosive
Burns skin & materials
Toxic
Can cause death
Irritant
Causes skin/eye irritation
Safety Rules in the Lab
- Wear safety goggles when heating or mixing chemicals
- Never eat or drink in the laboratory
- Tie back long hair and secure loose clothing
- Report all accidents to your teacher immediately
- Stand up when doing practical work
- Never touch chemicals with bare hands
Pure Substances & Mixtures
Understanding solutions and dissolving
Pure Substances
A pure substance contains only one type of particle. It has fixed properties like melting point and boiling point.
- • Distilled water (only H₂O molecules)
- • Oxygen gas (only O₂ molecules)
- • Copper metal (only copper atoms)
Mixtures
A mixture contains different types of particles mixed together but not chemically combined. They can be separated.
- • Salt water (salt + water)
- • Air (nitrogen, oxygen, etc.)
- • Granite (different minerals)
Dissolving
What happens when something dissolves?
The particles of the solute break apart and spread throughout
the solvent. They become surrounded by solvent particles. This
is why the solute seems to disappear - but it's still there!
Separating Mixtures
Methods for separating different types of mixtures
Filtration
Separates an insoluble solid from a liquid using filter paper.
Example: Sand and water - sand stays on filter paper (residue), water passes through (filtrate)
Evaporation
Separates a soluble solid from a solution by heating.
Example: Salt solution - water evaporates, salt crystals remain
Simple Distillation
Separates a liquid from a solution by boiling then condensing.
Example: Getting pure water from salt water - water boils, condenses in tube, collected separately
Chromatography
Separates dissolved substances based on how they move through paper.
Example: Separating ink colours - different dyes travel different distances up the paper
Elements, Atoms & Compounds
The building blocks of everything
Element
A substance made of only one type of atom. Cannot be broken down further.
Examples: Gold (Au), Oxygen (O), Carbon (C)
Atom
The smallest part of an element that can still be that element. Everything is made of atoms.
Atoms are too small to see even with a microscope!
Compound
Two or more elements chemically combined in fixed proportions.
Examples: Water (H₂O), Carbon dioxide (CO₂)
Molecules
A molecule is two or more atoms bonded together. This could be:
Element molecule: O₂ (two oxygen atoms bonded)
Compound molecule: H₂O (two hydrogen + one oxygen)
Chemical Reactions
Physical changes vs chemical changes
Physical Change
- No new substances formed
- Easy to reverse
- Only appearance changes
Examples: Melting ice, dissolving sugar, tearing paper
Chemical Change
- New substances ARE formed
- Very difficult to reverse
- Energy change often observed
Examples: Burning wood, rusting iron, baking a cake
Word Equations
We represent chemical reactions using word equations:
Example: When magnesium burns in oxygen:
Magnesium + Oxygen → Magnesium oxide
Acids, Bases & Alkalis
The pH scale and neutralisation
The pH Scale
The pH scale measures how acidic or alkaline a solution is. Click on different parts of the scale to learn more.
Click on the pH scale to see examples and details
Neutralisation
When an acid and an alkali react together, they neutralise each other:
Example: Hydrochloric acid + Sodium hydroxide →
Sodium chloride + Water
(This is how indigestion remedies work!)
Periodic Table
Organising the elements
Introduction to the Periodic Table
The Periodic Table organises all known elements by their properties. Elements are arranged in order of atomic number.
Groups (Columns)
Vertical columns. Elements in the same group have similar properties.
Periods (Rows)
Horizontal rows. Each period represents a new energy level.
Metals vs Non-metals
Metals
- • Shiny (lustrous)
- • Good conductors of heat and electricity
- • Malleable (can be hammered)
- • Ductile (can be drawn into wires)
- • High melting points
Non-metals
- • Dull appearance
- • Poor conductors
- • Brittle (break easily)
- • Lower melting points
- • Often gases at room temperature
Common Elements to Know
Hydrogen
Carbon
Nitrogen
Oxygen
Iron
Copper
Magnesium
Sulfur
Practice Questions
Test your understanding
Particle Model [3 marks]
Describe the arrangement and movement of particles in a solid.
Answer:
- • Arrangement: Particles are packed closely together in a regular pattern/structure [1 mark]
- • Movement: Particles vibrate in fixed positions - they cannot move around [1 mark]
- • Energy: Particles have low energy [1 mark]
Separating Mixtures [4 marks]
You have a mixture of sand, salt, and water. Describe how you would separate:
a) The sand from the salt water [2 marks]
b) The salt from the water [2 marks]
Answer:
Use filtration [1 mark]. Pour mixture through filter paper - sand (residue) stays on paper, salt water (filtrate) passes through [1 mark].
Use evaporation or simple distillation [1 mark]. Heat the salt water so water evaporates, leaving salt crystals behind [1 mark].
Chemical vs Physical Changes [3 marks]
Explain the difference between a physical change and a chemical change. Give one example of each.
Answer:
Physical change: No new substances are formed; only the appearance changes; easy to reverse [1 mark]. Example: melting ice, dissolving sugar, tearing paper [1 mark for any correct example].
Chemical change: New substances are formed; very difficult to reverse; often involves energy change [1 mark]. Example: burning wood, rusting iron, baking a cake [1 mark for any correct example].
Acids and Alkalis [4 marks]
a) What does the pH scale measure? [1 mark]
b) What colour would universal indicator show in a strong acid? [1 mark]
c) Write the word equation for neutralisation. [2 marks]
Mark Scheme:
a) [1 mark] The pH scale measures how acidic or alkaline a solution is (or concentration of H⁺ ions).
b) [1 mark] Red (strong acids are pH 1-2, universal indicator shows red).
c) [2 marks] Acid + Alkali → Salt + Water [1 mark for correct reactants, 1 mark for correct products].
Continue Learning
Explore Year 7 Physics or move on to Year 8 Chemistry.