Basic 7 · Science · Materials
States of Matter and the Importance of Liquids
In this topic you will classify materials into solids, liquids and gases using their properties, explain the arrangement of particles in each state, and discuss the importance of liquids to living things.
By the end of these notes you should be able to:
- Describe the properties of solids, liquids and gases
- Explain the arrangement and movement of particles in each state
- Discuss the importance of liquids in human life
What you already know
- Materials and their uses (Upper Primary)
Copy everything that has a blue line on its left into your notebook. The other parts are for reading.
Lesson 1
- Strand
- Diversity Of Matter
- Sub-strand
- Materials
- Indicator
- B7.1.1.1.1 – Classify materials into liquids solids and gases
Introduction
A stone, the water in a bottle and the air inside a balloon are all matter. Matter is anything that has mass and takes up space. It exists in three main states: solid, liquid and gas.
1. What Is Matter?
Matter: Anything that has mass and occupies space.
Everything around us is made of matter: the desk, the food we eat, the water we drink and the air we breathe. Scientists group matter into states according to how it behaves.
2. Properties of the Three States
| Property | Solid | Liquid | Gas |
|---|---|---|---|
| shape | fixed shape | takes the shape of its container | fills any container completely |
| volume | fixed volume | fixed volume | no fixed volume |
| compressibility | cannot be squeezed | hardly squeezed | easily squeezed |
| flow | does not flow | flows | flows and spreads |
| examples | stone, iron nail, wood, ice | water, palm oil, kerosene, milk | air, oxygen, carbon dioxide, steam |
3. Classifying Materials in the Environment
To classify a material, observe whether it keeps its shape, whether it flows and whether it fills its container. Sand looks as if it flows, but each grain is a tiny solid with a fixed shape, so sand is a solid. Smoke contains tiny solid particles mixed with gases. Some materials, like toothpaste and porridge, are thick liquids that flow slowly.
4. Testing Properties
You can test properties simply. Pour water from a cup into a bottle and notice that it changes shape but keeps the same volume. Press an inflated balloon gently and notice that the air inside can be squeezed. Try to squeeze a stone and notice that its shape and size do not change.
New words
- matter
- Anything that has mass and occupies space.
- solid
- Matter with a fixed shape and volume.
- liquid
- Matter with a fixed volume but no fixed shape.
- gas
- Matter with no fixed shape or volume.
Summary
- Matter exists as solids, liquids and gases.
- Solids have fixed shape and volume; liquids have fixed volume only; gases have neither.
- Materials are classified by observing shape, flow and compressibility.
Class activity: Classify the Materials
- Collect materials such as a stone, water, a balloon, sand, oil and a nail.
- Test each for shape, flow and compressibility.
- Record your results and classify each material.
You need: Stone, Water in a clear bottle, Inflated balloon
Exercises
Answer in your exercise book first, then check your answers.
1. Which is a gas?
- A. air
- B. stone
- C. water
- D. palm oil
Show answer
Answer: airNo fixed shape or volume.2. A liquid has…
- A. a fixed volume but no fixed shape
- B. a fixed shape
- C. no fixed volume
- D. no mass
Show answer
Answer: a fixed volume but no fixed shapeTakes the container's shape.3. Gases can be squeezed easily.
- A. True
- B. False
Show answer
Answer: TrueParticles are far apart.4. Anything that has mass and occupies space is ______.
Show answer
Answer: matterDefinition.5. Give two examples each of solids, liquids and gases.
Show answer
Answer: Solids: stone, wood; liquids: water, oil; gases: air, oxygen.Any correct.6. Explain why sand is classified as a solid even though it can be poured.
Show answer
Answer: Each grain has a fixed shape and volume; it is a collection of small solids, not a liquid.Grains are solids.
Lesson 2
- Strand
- Diversity Of Matter
- Sub-strand
- Materials
- Indicator
- B7.1.1.1.1 – Classify materials into liquids solids and gases
Introduction
Why can we walk through air but not through a wall? The answer lies in the tiny particles that make up all matter and how they are arranged.
1. The Particle Theory
Scientists believe all matter is made of tiny particles that are too small to see. These particles are always moving and are attracted to one another. How closely they are packed and how freely they move decide whether a substance is a solid, liquid or gas.
2. Particles in Each State
| State | Arrangement | Movement | Forces between particles |
|---|---|---|---|
| solid | closely packed in a regular pattern | vibrate in fixed positions | very strong |
| liquid | close together but irregular | slide past one another | fairly strong |
| gas | far apart and random | move quickly in all directions | very weak |
3. Explaining Properties with Particles
Solids keep their shape because their particles are held tightly in place. Liquids flow because their particles can slide over one another, but they keep their volume because the particles stay close together. Gases fill containers and can be compressed because their particles are far apart and move freely.
4. Changes of State
| Change | From → to | Example |
|---|---|---|
| melting | solid → liquid | ice melting in the sun |
| freezing | liquid → solid | water turning to ice in a freezer |
| evaporation or boiling | liquid → gas | water boiling in a pot |
| condensation | gas → liquid | water droplets on a cold bottle |
| sublimation | solid → gas directly | camphor balls getting smaller |
Heating gives particles more energy so they move faster and break free; cooling removes energy so particles slow down and come closer.
New words
- particle
- A tiny piece of matter.
- vibrate
- To move quickly back and forth in one place.
- melting
- Changing from solid to liquid.
- condensation
- Changing from gas to liquid.
Summary
- All matter is made of tiny moving particles.
- In solids particles are tightly packed, in liquids they slide past each other, and in gases they are far apart.
- Heating and cooling cause changes of state such as melting, evaporation and condensation.
Class activity: Particle Models
- Use bottle tops or beans to model particles in a solid, liquid and gas on a tray.
- Shake the tray gently to show particle movement.
- Explain each model to the class.
You need: Stone, Water in a clear bottle, Inflated balloon
Exercises
Answer in your exercise book first, then check your answers.
1. In which state are particles farthest apart?
- A. gas
- B. solid
- C. liquid
- D. all are the same
Show answer
Answer: gasWeak forces.2. Water droplets forming on a cold bottle is…
- A. condensation
- B. melting
- C. freezing
- D. sublimation
Show answer
Answer: condensationGas to liquid.3. Particles in a solid vibrate in fixed positions.
- A. True
- B. False
Show answer
Answer: TrueTightly held.4. Changing from solid to liquid is called ______.
Show answer
Answer: meltinge.g. ice to water.5. Explain why liquids can flow.
Show answer
Answer: Their particles are close together but can slide past one another.Particle movement.6. Explain what happens to the particles when ice melts.
Show answer
Answer: Heat gives the particles energy; they vibrate more and break out of their fixed positions, sliding past each other as a liquid.Energy and movement.
Lesson 3
- Strand
- Diversity Of Matter
- Sub-strand
- Materials
- Indicator
- B7.1.1.2 – Discuss the importance of liquids in the life of humans
Introduction
We drink water, cook with palm oil, enjoy fruit juice and fuel cars with petrol. Life would be impossible without liquids.
1. Water: The Most Important Liquid
Water makes up about 60 percent of the human body. It carries nutrients and oxygen in the blood, removes wastes in urine and sweat, keeps body temperature steady and helps digestion. Plants need water for photosynthesis and to carry minerals from the soil. Animals need water to survive, and many live in it.
2. Other Important Liquids
| Liquid | Uses |
|---|---|
| water | drinking, cooking, washing, farming, generating electricity |
| palm oil and vegetable oil | cooking, soap making, body cream |
| milk | food for babies and adults, rich in calcium and protein |
| fruit juice | provides vitamins and refreshment |
| petrol, diesel and kerosene | fuel for vehicles, generators and lamps |
| blood | carries oxygen, food and wastes in the body |
| medicines (syrups) | treat illnesses |
3. Liquids in Industry and Transport
Many industries depend on liquids. Water cools machines and is used in making drinks and paper. Crude oil is refined into petrol, diesel and lubricants. Water stored behind the Akosombo and Bui dams turns turbines to produce electricity. Rivers and Lake Volta are used for transport.
4. Using Liquids Safely and Wisely
Some liquids are dangerous. Petrol and kerosene catch fire easily, and chemicals such as bleach and acids can burn the skin. Store them in labelled containers out of the reach of children. Water must be clean before drinking to avoid cholera and typhoid; boiling or filtering helps. Save water by turning off taps and reusing water for plants.
New words
- nutrient
- A substance in food needed for growth and health.
- fuel
- A material burned to produce energy.
- flammable
- Able to catch fire easily.
- conserve
- To use carefully and avoid waste.
Summary
- Water is essential for drinking, body processes, farming and electricity.
- Liquids such as oil, milk, juice and fuels have many uses at home and in industry.
- Dangerous liquids must be stored safely, and water should be clean and conserved.
Class activity: Liquids Survey
- Examine bottles of water, palm oil and fruit juice.
- List the uses of each and how they help living things.
- Present a poster on the importance of liquids.
You need: Bottle of clean water, Bottle of palm oil, Bottle of fruit juice
Exercises
Answer in your exercise book first, then check your answers.
1. About how much of the human body is water?
- A. 60 percent
- B. 10 percent
- C. 90 percent
- D. 5 percent
Show answer
Answer: 60 percentMost of the body.2. Which liquid is used as fuel?
- A. kerosene
- B. milk
- C. fruit juice
- D. palm oil
Show answer
Answer: keroseneBurns for energy.3. Petrol is flammable.
- A. True
- B. False
Show answer
Answer: TrueCatches fire easily.4. A material burned to produce energy is a ______.
Show answer
Answer: fuele.g. petrol.5. State three uses of water in the human body.
Show answer
Answer: Carries nutrients, removes wastes, controls body temperature (or aids digestion).Any three.6. Explain how water is used to generate electricity in Ghana.
Show answer
Answer: Water stored behind dams such as Akosombo flows through turbines that turn generators.Hydroelectric power.
Homework
- Make a table of ten materials at home classified as solids, liquids or gases.