Chemistry, 7–10 years — 20 topics · MyLeoNes™ Kuks
20 chemistry topics written for 7–10 years — not a older text simplified. In teaching order, each a deck of five cards: the idea, why it exists, a worked example, the common trap and where you meet it.
Chemistry · 7–10 years
States of matter
The same material can be a solid, liquid or gas. Its state helps explain why ice keeps its shape, water flows and steam spreads.
Dissolving
When a substance dissolves, it spreads through a liquid so evenly that we can no longer see separate pieces. It has not vanished.
Separating mixtures
A mixture contains different materials together, but they keep their own properties. Those properties can help us separate the mixture again.
Making new substances
Sometimes materials change into substances with new properties. Bubbles, a new colour or a solid appearing can be clues, but we must compare carefully before deciding.
Atoms and molecules
Everything around us is made from tiny building blocks. Atoms and molecules are too small to see, but they help us explain what materials are made of and why they behave differently.
Choosing materials by their properties
A material is useful because of what it can do, not just because of its name. Looking at properties such as hardness, flexibility, waterproofing and conductivity helps us choose the right material for a job.
Density: how much matter fits
Some objects are heavy for their size and others are light for their size. Density helps compare how much matter is packed into the same amount of space, which explains why some things float and others sink.
Acids, bases and indicators
Some liquids are acidic, some are basic, and many are neither strongly acidic nor strongly basic. Indicators change colour to give us clues about this, without needing to taste or touch a substance.
Where does the matter go?
When substances change, the matter does not simply vanish. This idea helps us account for what goes in and what comes out, even when a gas is hard to see.
Energy stored in chemicals
Some substances can release energy when they change, while others take in energy during a change. This explains why food can power a body and a battery can power a torch.
What fire needs
Fire is a fast chemical change that needs fuel, oxygen and enough heat. Remove any one of these and the flame goes out, which is why this is useful for both lighting and safety.
Why iron rusts
Rust is a new, crumbly material made when iron reacts slowly with oxygen and water. Knowing what rust needs helps us protect bridges, bicycles and tools from damage.
How plants make food
Plants do not eat sandwiches or take food from the soil. Using light, water and carbon dioxide from the air, their green parts make sugar and release oxygen.
What food is made of
Food is not one single substance. Sugars and starches give quick fuel, fats store energy, proteins help build and repair the body, and vitamins and minerals help it work properly.
How soap removes grease
Water alone runs over greasy dirt without mixing with it. Soap has one end that interacts with water and another that attaches to grease, so rubbing and rinsing can carry the dirt away.
How yeast makes dough rise
Yeast is a living microorganism used in bread-making. It uses sugar and releases carbon dioxide gas; bubbles of that gas become trapped in the dough and make it expand.
Why some reactions happen faster
Temperature and surface area can change how quickly a chemical reaction happens. This explains why a crushed tablet fizzes faster and why food cooks differently at different temperatures.
Helpers that speed up reactions
Some substances make a chemical reaction faster without being used up themselves. Enzymes in living things are natural examples, and this idea helps explain digestion and some cleaning products.
How crystals grow
A crystal grows when particles arrange themselves in a repeating pattern. Salt and sugar crystals show this clearly, and their flat faces and regular shapes come from the way their particles fit together.
Plastics are long chains
Many plastics are polymers: very long molecules made by joining many small repeating parts. Their chain structure can make them light, flexible or tough, but it also means many plastics break down slowly in nature.
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