Chemistry · Professor Curie

Every card in Atoms, elements and compounds, Year 7: more practice

The whole deck, in order — so you can read it through before your child ever sees it.

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1 KS3-CHEM-ATO-0027

Which of these is a compound: iron, water or air?

Water

HintA compound has two or more different elements joined together chemically.

WhyWater is hydrogen and oxygen chemically joined in a fixed ratio. Iron is an element and air is a mixture of gases.

2 KS3-CHEM-ATO-0028

An element is a substance made of only one type of ____.

atom

HintEvery particle in a sample of the element is the same kind.

WhyCopper contains only copper atoms and oxygen gas contains only oxygen atoms. A compound contains different types of atom chemically joined.

3 KS3-CHEM-ATO-0029

What is the chemical symbol for potassium? (letters only)

K

HintIt does not start with P, because P stands for phosphorus.

WhyThe symbol K comes from the Latin name kalium. Several symbols come from Latin names, such as Na for sodium and Fe for iron.

4 KS3-CHEM-ATO-0030

Which element has the chemical symbol Fe? (one word)

Iron

HintThe symbol comes from its Latin name, not its English one.

WhyFe is short for ferrum, the Latin word for iron. Fe is also in the word ferrous, as in iron-rich foods.

5 KS3-CHEM-ATO-0031

Which formula shows a molecule of a compound: O2 or CO2?

CO2

HintLook at how many different elements each formula contains.

WhyCO2 has two different elements, carbon and oxygen, joined together. O2 is also a molecule, but of an element, because both atoms are oxygen.

6 KS3-CHEM-ATO-0032

Salty water is a mixture. Which simple method gets the salt crystals back without any chemical reaction?

Evaporating the water

HintHeat gently until the liquid has gone.

WhyIn a mixture the substances keep their own properties, so they can be separated by physical methods. No new substance is made.

7 KS3-CHEM-ATO-0033

Air contains nitrogen, oxygen and other gases that keep their own properties. Is air a compound or a mixture?

A mixture

HintThe gases in air are not chemically joined to each other.

WhyThe gases in air are just mixed together and can be present in different amounts. In a compound, the elements are chemically joined in a fixed ratio.

8 KS3-CHEM-ATO-0034

Is cooking an egg a physical change or a chemical change?

A chemical change

HintCan you turn a cooked egg back into a runny egg?

WhyHeating changes the proteins in the egg and a new substance forms, so it cannot be undone. A physical change, such as melting, keeps the same substance.

9 KS3-CHEM-ATO-0035

Hydrogen burns explosively and oxygen makes fires burn fiercer. What compound do they form that is used to put out fires? (one word)

Water

HintThink about what firefighters spray.

WhyHydrogen and oxygen join to make water, which behaves nothing like either gas. A compound has its own properties.

10 KS3-CHEM-ATO-0036

Why is a compound not simply 'a bit of each ingredient'?

It is a new substance with its own properties

HintCompare table salt against the metal and the poisonous gas it is made from.

WhyWhen elements join chemically they make a new substance with different properties from the elements. That is why each new compound needs its own safety check.

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