Science notes, unit 8

Matter

Textbook Science Year 5 (DLP), pages 177–198

What this chapter covers

You can name the three states of matter and give examples of each in your surroundings (8.1.1)
You can state the properties of solid, liquid and gas: mass, volume, shape and space (8.1.2, 8.1.3, 8.1.5)
You can name the three states of matter of water (8.1.4)
You can describe how particles are arranged in a solid, a liquid and a gas (8.2.1)
You can name the processes of melting, freezing, boiling, evaporation and condensation, and say whether heat is gained or lost (8.2.1, 8.2.2)
You can explain how clouds and rain form in the natural water cycle (8.2.3)
You can give examples of changes of state in daily life and explain them (8.2.4)

Everything around you is made of matter: the sand on the beach, the sea and the wind that flies your kite. In this unit you will learn the three states of matter, their properties and how water changes from one state to another.

8.1States of matter

Matter is anything that has mass and occupies space. All living things and non-living things are made of matter.

Matter exists in three states: solid, liquid and gas. On the beach we can find all three.

A beach scene with a girl building a sandcastle, a boy splashed by seawater and a boy flying a kite — Sand is a solid. Seawater is a liquid. The wind is a gas.

Example: classifying matter

Solid: notebook, paper clip, dice, spoon, biscuit.
Liquid: drinking water, soy sauce, palm oil, sweat.
Gas: air, oxygen, carbon dioxide, water vapour.

Properties of solid, liquid and gas

Each state has its own properties. In the textbook activities you weigh a stone, pour coloured water into different containers and inflate balloons to find them.

Property	Solid	Liquid	Gas
Has mass	Yes	Yes	Yes
Occupies space	Yes	Yes	Yes
Volume	Fixed	Fixed	Not fixed
Shape	Fixed	Not fixed (takes the shape of its container)	Not fixed (fills its container)

All three states have mass and occupy space. Do not say "a gas has no mass". A balloon with air is heavier than the same balloon without air.

Solid: pressing a small stone does not change its shape.
Liquid: water pours into a cup, a flask or a glass container and takes the shape of each one, but its volume stays the same.
Gas: air fills a balloon and spreads out in all directions. When you push the piston of a syringe with the tip covered, the air is pushed into a smaller space.

Example: volume of a stone

The water in a measuring cylinder is at 40 mL. After a stone is put in, it rises to 62 mL.
Volume of stone = final volume − initial volume = 62 − 40 = 22 mL.

Two measuring cylinders: water at 40 mL before the stone is added and 62 mL after — The stone pushes the water level up from 40 mL to 62 mL.

Finding the mass of a liquid. Subtract in the same way: mass of water = mass of beaker with water − mass of empty beaker. If a beaker with water has a mass of 245 g and the empty beaker is 95 g, the water has a mass of 150 g.

Which state of matter has a fixed volume but no fixed shape?

Show answerHide answer

Liquid.

Particles in matter

Matter is made of very tiny particles. The arrangement of the particles is different in each state.

Three circles of particles: closely packed and orderly in the solid, less packed and not orderly in the liquid, spread out in the gas — Particles of a solid, a liquid and a gas (drawn for this site).

State	Arrangement of particles
Solid	Very closely packed and arranged in an orderly way
Liquid	Less packed and not in an orderly way
Gas	Spread out and not in an orderly way

8.2Changes in the state of matter of water

Water can exist in all three states.

State	Name
Solid	Ice
Liquid	Water
Gas	Water vapour

Comic strip of Mr Ice running with Mr Rock on the beach, melting in the sun and then disappearing as water vapour — Mr Ice melts into water and then becomes water vapour in the hot sun.

Five processes

The state of water changes when it gains heat from the surroundings or loses heat to the surroundings.

Solid melts to liquid and liquid boils or evaporates to gas when heat is gained; gas condenses to liquid and liquid freezes to solid when heat is lost — Gaining heat: melting, boiling and evaporation. Losing heat: freezing and condensation.

Process	Change	Heat	Example
Melting	Solid to liquid	Gained	Ice cream melts; ice cubes in a petri dish become water
Freezing	Liquid to solid	Lost	Water becomes ice cubes in a freezer
Boiling	Liquid to gas	Gained	Water in a kettle at 100 °C makes water vapour
Evaporation	Liquid to gas	Gained	Wet clothes dry on a clothes line
Condensation	Gas to liquid	Lost	Dew on leaves; a foggy mirror above hot water

Boiling happens only at the boiling point of water, 100 °C. Evaporation happens at any temperature below the boiling point.

Boiling and evaporation both change a liquid into a gas, but they are not the same. Wet clothes dry by evaporation, not boiling. Never say "the clothes boiled".

Did you know? Mr Borhan's spectacles go foggy when he leaves his air-conditioned car. Warm water vapour in the air touches the cold lenses and loses heat, so it condenses into tiny water droplets.

A kettle of water is heated until steam comes out. Name the process and say whether the water gains or loses heat.

Show answerHide answer

Boiling (liquid to gas). The water gains heat.

Simple investigations

Activity	What you do	What happens	Process
1	Put a test tube of coloured water in a box of ice and salt	The water becomes solid after 30 minutes	Freezing
2	Leave ice cubes in a petri dish for 10 minutes	The ice becomes water	Melting
3	Heat 150 mL of water in a beaker	Bubbles and steam form at 100 °C	Boiling
4	Leave two drops of water in the sun for 20 minutes	The water disappears	Evaporation
5	Place a mirror above hot water, then lift it	Water droplets form on the mirror	Condensation

Be careful with the Bunsen burner. Use a test tube holder to lift hot things, and always have an adult nearby.

Clouds and rain: the natural water cycle

The quantity of water on the Earth is always kept the same by the natural water cycle. It involves evaporation and condensation of water.

Water cycle: 1 water evaporates from the sea, 2 water vapour condenses into a cloud, 3 rain falls, 4 water flows back to the sea — The natural water cycle (drawn for this site, following textbook pp. 192–193).

The heat from the Sun makes water from soil, oceans, rivers and lakes evaporate into water vapour.
Water vapour rises, cools and condenses into tiny water droplets that form clouds.
Higher up, cold air makes the droplets join into bigger clouds. The clouds become heavy and the water falls as rain.
Rainwater soaks into the ground and flows back to lakes, rivers and oceans. The cycle starts again.

What would happen if evaporated water never fell back as rain?

Show answerHide answer

Lakes, rivers and oceans would slowly dry up, and plants, animals and people would not have enough water.

Pictures: Science Year 5 (DLP) textbook, pp. 177–198 (beach p. 178, Mr Ice story p. 184). The particle diagrams, state-change diagram, measuring cylinders and water cycle are drawn for this site.

Summary

Idea	Remember
Matter	Has mass and occupies space; solid, liquid or gas
Solid	Fixed shape and volume; particles closely packed and orderly
Liquid	Fixed volume, no fixed shape; particles less packed
Gas	No fixed shape or volume; particles spread out
Gains heat	Melting, boiling, evaporation
Loses heat	Freezing, condensation
Water cycle	Evaporation then condensation, then rain; keeps the quantity of water on Earth the same