Primary 3 Science · Key notes
Key Notes and Word Bank: All Seven Chapters
One short summary for every chapter, written to match what children learn in class. Read a chapter, say the key words out loud, then try the Think about it question.
Chapter 1: Diversity of Living and Non-living Things
- Diversity means the great variety of living and non-living things around us. We group things by their similarities. Grouping is called classification, and we can show it with pictures, a table or a graphic organiser.
- Living things need water, food and air. Animals eat other living things for food. Plants make their own food using light. Land animals cannot stay underwater for long because they breathe air that contains oxygen.
- Living things can grow (get bigger and more complex), respond to changes (an eyelid shuts in bright light, a plant grows towards the window, mimosa leaves fold when touched) and reproduce (make more of their own kind).
- Reproducing matters because living things that cannot survive become extinct, which means they all die out.
- Some animals give birth to live young. Others lay eggs. Insects such as mosquitoes lay many eggs at one time because so many young do not survive.
diversityclassificationoxygenrespondreproduceextinct
Think about it: Scientists argued for over 100 years about whether a virus is living or non-living. Which of the three living-thing abilities would you test first?
Chapter 2: Classification of Living Things
- Scientists sort living things into four main groups: plants, animals, fungi and bacteria. Carolus Linnaeus gave every living thing a two-part name, called binomial nomenclature. Humans are Homo sapiens.
- Plants make their own food and have roots, stems and leaves; some reproduce by seeds and others by spores. Animals cannot make their own food and move to find it.
- Animal groups: amphibians (moist skin, lay eggs in water, young are tadpoles), birds (feathers, wings, beaks, lay eggs), fish (fins, scales, gills), insects (six legs, three body parts, feelers), reptiles (dry scaly skin, lungs), and mammals (hair or fur, feed milk to their young, warm-blooded).
- Warm-blooded animals keep a constant body temperature. Cold-blooded animals have a body temperature that changes with their surroundings.
- Fungi (mould, mushrooms, yeast) do not make their own food and reproduce by spores. Some are useful (yeast, edible mushrooms, tempeh) and some are harmful (bread mould).
- Bacteria are tiny living things. Some make us sick, so we wash our hands. Some are useful, such as the ones in yoghurt. Fleming discovered the first antibiotic by noticing mould that stopped bacteria growing.
classificationamphibianmammalwarm-bloodedfungisporebacteria
Think about it: A starfish lives in water but is not a fish. Which fish features is it missing?
Chapter 3: Diversity of Materials
- Objects are made from materials: wood, metal, ceramic, rubber, glass, plastic and fabric. Wood comes from trees, metals are dug from the ground, ceramic is baked clay, glass is melted sand, plastic is made from oil, rubber comes from tree sap or oil, and fabric comes from plants or animals.
- A physical property is something we can measure or observe. Five to know: strength, flexibility, floating or sinking, waterproof and transparency.
- Transparent materials let most light through, translucent ones let some through, and opaque ones let none through.
- A metal ship floats because of the air trapped inside it. A material can change when it is treated: strong wood becomes easy-to-tear paper, and fabric becomes waterproof with a layer of wax.
- We choose a material for the job its properties suit. The same object can be made of different materials, and an object with many parts may use several materials, such as a car with rubber tyres and glass windows.
materialphysical propertystrengthflexibilitywaterprooftransparenttranslucentopaque
Think about it: Design a school bag. Which material would you pick for the strap, the body and the zip, and why?
Chapter 4: Life Cycles of Plants
- A life cycle is a repeated pattern of change as a living thing grows and reproduces. Life cycles let living things of the same kind keep living on Earth.
- A plant has three stages: the seed, the young plant and the adult plant. The adult plant makes new seeds, and the pattern starts again.
- We can use our five senses and simple tools such as a ruler to record how a seed grows.
- Some plants are in danger of dying out, so people protect them, for example in seed banks and in herbariums that keep dried plant specimens.
- Not all plants grow from seeds. Ferns reproduce by spores.
life cycleseedyoung plantadult plantspore
Think about it: Why is it important to keep seeds safe in a seed bank?
Chapter 5: Life Cycles of Animals
- Animals have either three stages (egg, young, adult) or four stages (egg, larva, pupa, adult).
- Three stages: chicken (young is a chick, looks like the adult), frog (young is a tadpole, does not look like the adult), grasshopper and cockroach (young is a nymph, grows by moulting).
- Four stages: beetle, butterfly and mosquito. The young (larva) does not look like the adult. A butterfly caterpillar has six legs and extra false legs called prolegs.
- Moulting means shedding the outer skin as the young insect grows bigger.
- Mosquitoes lay eggs in still water. Some spread dengue. Stop dengue with B-L-O-C-K and remove stagnant water.
- Compare life cycles by counting the stages and by checking whether the young look like the adult.
egglarvapupanymphmoultstagnant water
Think about it: The textbook asks: which comes first, the egg or the adult? Explain why a cycle has no real start.
Chapter 6: Properties of Magnets
- A magnet attracts objects made of magnetic materials: iron and steel. Ceramic, fabric, glass, plastic, rubber and wood are non-magnetic. Some metals, such as aluminium, are non-magnetic too.
- Every magnet has two poles, a North pole and a South pole. The poles are where the pull is strongest, so most clips stick there.
- Unlike poles attract and like poles repel. An object that repels a magnet is surely a magnet.
- Iron powder around a magnet shows a pattern called the magnetic field.
- A freely suspended magnet or a compass needle settles pointing North-South, because Earth behaves like a giant magnet.
magnetmagneticnon-magneticpoleattractrepelcompass
Think about it: Which parts of a bar magnet would pick up the most pins if you dipped it in a pile?
Chapter 7: Making and Using Magnets
- An object made of iron or steel can be made into a magnet by the stroke method or the electrical method. This is called magnetising it.
- The electrical method: wind wire around an iron nail and connect it to a battery to make an electromagnet. Switch off the battery and the clips drop.
- To make an electromagnet stronger, use more turns of wire or more batteries. Do not leave it connected for too long, do not touch the bare wires and never connect it to the mains.
- In a fair test only one thing (the variable) is changed and everything else is kept the same. Repeat the test to be sure of the results.
- Uses: fridge door strips, a scrapyard crane with an electromagnet, steel whiteboards, MRI scanners and electric motors in fans and washing machines.
magnetisestroke methodelectromagnetfair testvariableelectric motor
Think about it: How would you test whether the number of batteries changes the strength of an electromagnet?
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