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Elements & Compounds Worksheet

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Elements & Compounds Worksheet

Charlie and Harper are checking products at a supermarket. Use the clues and your knowledge of atoms, elements and compounds to solve each task. A chemical formula shows which atoms are present and how many: for example, H₂O contains hydrogen and oxygen atoms.

Investigate the ingredients

Use the formula clues in Questions 1–4. Remember: an element contains one type of atom; a compound contains two or more different elements chemically bonded.

1.Harper finds aluminium foil labelled Al. Is aluminium an element or a compound? Explain what the symbol tells you.

2.Charlie sees water (H₂O), carbon dioxide (CO₂) and oxygen gas (O₂) in a science display. Which substance is the compound?

Water only
Water and carbon dioxide
Oxygen only
All three

3.Match each supermarket substance to its formula: table salt, water, carbon dioxide. Formulas: NaCl, H₂O, CO₂.

Table salt
Water
Carbon dioxide

H₂O
CO₂
NaCl

4.A sealed packet contains pure nitrogen gas, N₂. True or false: nitrogen gas is a compound because each molecule has two atoms. Explain your choice.

Read the particle clues

In the models below, each letter is an atom. A joined group represents atoms chemically bonded into a particle. Different letters stand for different elements.

Model A: ●—● ●—● ●—● Each pair is made of identical atoms.

Model B: ●—○ ●—○ ●—○ Each pair is made of two different atoms.

5.Which model shows a compound? Give one piece of evidence from the particle arrangement.

6.A water molecule has the formula H₂O. How many hydrogen atoms and how many oxygen atoms are in one molecule?

Explain and apply

Use precise science language: elements are substances made of one type of atom, while compounds contain different elements chemically bonded in fixed proportions.

7.Anh-Mae says, “Salt is a mixture because it contains sodium and chlorine.” Explain why table salt (NaCl) is classified as a compound instead.

8.Complete the statement: Carbon dioxide, CO₂, contains carbon atom(s) and oxygen atom(s) in each molecule.

9.A student wants to separate water into hydrogen and oxygen. Would filtering or electrolysis be suitable? Name the method and explain why it works.

10.At the supermarket, Harper finds a pure substance with the formula Cu. Charlie finds a pure substance with the formula NH₃. Identify each as an element or compound and justify both answers.