Class 6–8: Science you can play with

Try at home: Hold a magnifying glass between a window and a white wall or paper. Move it until you see a sharp, upside-down picture of the window. A lens can form an image on a screen.

Lens

A curved piece of glass or plastic that bends light.

Image

The picture of an object formed by a lens or mirror.

Focus

The point where light rays meet after passing through a lens.

Try at home: Put a steel spoon and a plastic or wooden spoon in the same cup of hot tea or water (ask an adult). After a minute, gently touch the handles. Which one carried the heat up to your hand?

Conduction

Heat moving through a solid from the hot part to the cold part.

Conductor

A material that lets heat pass easily, like metal.

Insulator

A material that slows heat down, like wood or plastic.

Try at home: Rest a book on a tray and slowly lift one end. Note how steep it is when the book starts to slide. Try again with a sheet of paper or a cloth under the book. Which surface needs the steeper slope?

Friction

A force that resists one surface sliding over another.

Slope

How steep a surface is.

Force

A push or a pull.

Try at home: Sprinkle a few pins or paper clips near a magnet and see which way they point. With an adult, wind wire around an iron nail and touch the ends to a cell for a moment: the nail becomes a magnet.

Magnet

An object that attracts iron and has north and south poles.

Magnetic field

The space around a magnet where its force acts.

Electromagnet

A magnet made by passing current through a coil of wire.

Try at home: Tie a key or a small bag to a string about 50 cm long and let it swing gently. Count 10 swings with a clock and divide by 10. Now halve the string and time it again. Shorter string, faster swing?

Pendulum

A weight on a string or rod that swings to and fro.

Period

The time for one full swing, there and back.

Oscillation

Any motion that repeats again and again.

Try at home: With an adult, boil a few red cabbage leaves in water and let it cool: the purple water is an indicator. Add a few drops to lemon juice, then to soap water. Acids and bases turn it different colours.

Acid

A sour substance, like lemon juice or vinegar.

Base

A bitter, soapy substance, like baking soda in water.

Indicator

A substance that changes colour in an acid or a base.

Neutralisation

When an acid and a base cancel each other out.

Try at home: Draw a thick dot with a black washable marker 2 cm from the bottom of a strip of kitchen paper. Dip the very bottom in a little water, keeping the dot above the water. Watch the ink split into colours.

Mixture

Two or more substances mixed together.

Chromatography

A way to separate the colours or parts of a mixture.

Solvent

The liquid that carries the substances, here water.

Try at home: Drop one drop of food colour into a glass of cold water and another into warm water (ask an adult). Do not stir. Watch which glass mixes faster.

Diffusion

Particles spreading out and mixing on their own.

Particle

A tiny piece of matter, too small to see.

Temperature

How hot or cold something is; hotter particles move faster.

Try at home: Stir salt into a glass of water one spoon at a time. Count the spoons until salt stays at the bottom. That water is now saturated. Ask an adult to warm it a little: can it take one more spoon?

Dissolve

When a solid mixes into a liquid and seems to disappear.

Solution

A liquid with something dissolved in it.

Saturated

A solution that cannot dissolve any more at that temperature.

Try at home: Pick an animal you saw today, like a crow or a lizard. Draw what it eats and what eats it, and keep going down to a plant. Join the arrows: you have made a food chain.

Producer

A living thing that makes its own food, like a plant.

Consumer

An animal that eats plants or other animals.

Food chain

Who eats whom, in a line from plants to animals.

Try at home: Cover part of a leaf on a potted plant with a strip of black paper for a few days. Then remove it. The covered part looks paler because it got no light to make food.

Photosynthesis

How green plants make food from sunlight, water and carbon dioxide.

Chlorophyll

The green colour in leaves that captures sunlight.

Oxygen

The gas plants give out, which we breathe in.

Try at home: Toss a coin 10 times and count heads. Then toss it 50 times. With more tosses, the share of heads gets closer to one half. That is chance at work.

Chance

How likely something is to happen.

Probability

Chance written as a number from 0 (never) to 1 (always).

Estimate

A good guess based on information.

Try at home: Wrap one cup of warm water in a towel and leave another cup bare (ask an adult for the water). Check both after 20 minutes. The wrapped cup stays warmer because the towel is an insulator.

Insulation

Material that slows down the loss of heat.

Heat loss

Heat escaping from a warm place to a colder one.

Window glazing

The glass in a window; two layers keep heat in better.

Try at home: Look at a bicycle. Count the teeth on the front gear and the back gear. Turn the pedal once slowly and count how many times the back wheel turns.

Gear

A wheel with teeth that turns another wheel.

Ratio

How many times bigger one number is than another.

Speed

How fast something turns or moves.

Try at home: Stand a pencil upright in clay in a sunny spot. Mark the tip of its shadow every hour. The shadow moves and changes length as the sun crosses the sky.

Shadow

A dark shape where an object blocks light.

Sunrise and sunset

When the sun appears and disappears as the Earth turns.

Tilt

How much something leans; solar panels are tilted towards the sun.

Try at home: Place a wide bowl outside the next time it rains and measure the water depth with a ruler. Multiply by your roof area to guess how much rain your roof collects.

Rainwater harvesting

Collecting and storing rain to use later.

Rainfall

How much rain falls, measured in millimetres.

Tank

A container that stores water.

Try at home: For one day, sort your home's waste into paper, plastic, metal and food. Which pile is biggest? Which items could be reused or recycled instead of thrown away?

Recycle

To turn used material into something new.

Reuse

To use something again instead of throwing it away.

Waste

Things we throw away.