LOWKEY SMART

Read big numbers in groups of three digits: first the thousands, then the hundreds, tens and ones.

Everything is made of tiny particles. In a solid, the particles are packed tightly in fixed places, so a solid keeps its own shape. In a liquid, the particles are close together but can slide past each other, so a liquid flows and takes the shape of its container. In a gas, the particles are far apart and move quickly, so a gas spreads out to fill any space. Heating a solid can make it melt into a liquid: ice melts at 0°C. Heating a liquid makes it evaporate into a gas, and water boils at 100°C. Cooling a gas turns it back into a liquid, which is called condensation, and cooling a liquid turns it into a solid, which is called freezing.

The Year 5 and 6 spelling words often break simple rules, so learn them in parts and check the tricky letters carefully. Watch for double letters, such as the two cs and two ms in accommodate, and soft sounds, such as the c and two s's in necessary. Say each part aloud as you spell it: ne-cess-ary, em-barr-ass.

The Sun is a star at the centre of our solar system. Eight planets orbit (travel around) the Sun. In order from the Sun they are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Earth takes about 365 days, which is one year, to orbit the Sun once. The Moon orbits the Earth and takes about 28 days to go round once. The Sun, Earth and Moon are all roughly spheres (ball shapes). The Moon does not make its own light: we see it because it reflects light from the Sun.

A relative clause adds extra information about a noun and usually starts with who, which, where, whose or that. It comes straight after the noun it describes. For example: The chef, who had trained in Paris, won the competition.

The Earth spins on its axis, an imaginary line through the North and South Poles. It turns round once every 24 hours. The half of the Earth facing the Sun has day, and the half facing away from the Sun has night. Because of the way the Earth spins, the Sun appears to rise in the east and set in the west. The Sun is not really moving across our sky: it only seems to move because the Earth is turning. At midday the Sun is at its highest in the sky, so shadows are at their shortest.

The forecast had promised nothing more than a light shower, so nobody expected the sky to turn the colour of a bruise by mid-afternoon. Elsi stood at the harbour wall with her uncle, watching the fishing boats race back before the wind picked up. He explained that sailors read the clouds the way other people read a clock: towering, anvil-shaped clouds meant a storm was building fast. Within minutes, the first boats were tying up, their crews shouting instructions to each other over the rising gusts. Elsi's uncle gripped the railing as spray flew over the wall and soaked their coats. When the rain finally arrived, it came sideways, stinging their faces. Elsi had never felt so small next to the sea, yet she did not want to move from the wall until the last boat was safely in.

We choose a material for a job because of its properties. A transparent material, like glass, lets light through so you can see through it; an opaque material, like wood, does not let light through. A thermal insulator, like wool or plastic, slows down heat moving through it; a thermal conductor, like metal, lets heat through easily. Metals also let electricity flow through them, while plastic is an electrical insulator, so it stops electricity. Magnetic materials are pulled towards a magnet: iron and steel are magnetic, but most other metals, such as copper and aluminium, are not. A material is flexible if it bends without breaking.

Brackets, a pair of commas or a pair of dashes can all be used to add extra information to a sentence that could be removed without changing its main meaning. For example: The comet (which only appears every seventy years) lit up the night sky. My cousin, who lives in Leeds, is visiting in June.

When a solid such as sugar or salt mixes into water and seems to disappear, it has dissolved, and the mixture is called a solution. A material that dissolves is soluble. Sand does not dissolve in water, so it is insoluble. Stirring, or using warmer water, makes sugar dissolve faster. You can separate sand from water by filtering: the water passes through filter paper and the sand is left behind. You can separate big solids, like stones, from small ones, like sand, with a sieve. To get salt back from salty water, you evaporate the water by leaving it somewhere warm, and the salt is left behind.

Words often share a Latin or Greek root that carries their core meaning: spect comes from Latin and means to look, so inspect and spectator both involve looking. Knowing synonyms (words with a similar meaning) and antonyms (words with an opposite meaning) helps you choose the most precise word.

Every question here takes more than one step, so write the steps down. Read it twice, decide what is being asked, then work through. It pulls together angles (straight line 180°, around a point 360°).

A force is a push or a pull, and forces are measured in newtons (N). Gravity is a pull force: it pulls everything towards the centre of the Earth, which is why things fall when you drop them. Your weight is the force of gravity on you, while your mass is how much matter you are made of, measured in kilograms (kg). Air resistance is a force that slows down things moving through air. A parachute has a large surface area, which gives lots of air resistance. Water resistance slows down things moving through water, so fish and boats have streamlined shapes that let them move easily. Friction acts when two surfaces rub together, and a rough surface gives more friction than a smooth one.

Bats are often misunderstood, yet they are some of the most useful creatures in the UK. A single pipistrelle bat, one of Britain's smallest species, can eat around three thousand insects in a single night. Farmers benefit hugely from this appetite, since bats devour many pests that would otherwise damage crops. Unlike birds, bats navigate in complete darkness using echolocation: they send out high-pitched calls and listen for the echo bouncing back off nearby objects. This allows them to dodge branches and catch moths in mid-air with astonishing accuracy. Sadly, bat numbers have declined across Britain, mainly because their roosting sites in old barns and hollow trees keep disappearing. Conservationists now encourage people to put up bat boxes in gardens, giving these remarkable mammals somewhere safe to rest during the day.