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Elements and Compounds Worksheet

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Elements and Compounds Worksheet

At an airport science-exhibition kiosk, Xavier and Evie are checking labels on everyday materials. Use the particle key and your science knowledge to solve each task. An element contains one type of atom; a compound contains different elements chemically bonded.

Particle key

Each symbol is one atom. Atoms touching are bonded. Different colours represent different elements.

Sample A 🔵 🔵 🔵 Three separate atoms of the same element

Sample B 🔴—🔴 🔴—🔴 Two molecules, each made of the same element

Sample C 🔴—🔵 🔴—🔵 Two molecules, each made of two different elements

Sample D 🔴—🔵—🔵 🔴—🔵—🔵 Two identical molecules made from two elements

1.Which sample represents an element made of single, unbonded atoms? Choose the sample letter.

2.Which samples are compounds? Explain how the particle key shows this.

3.Sample B is made of bonded pairs of identical atoms. Is it an element or a compound? Explain.

An element, because it contains only one type of atom.
A compound, because its atoms are bonded.
A mixture, because it has two molecules.

Read the baggage-label investigation

The airport materials team checks substances used around the terminal. A sample of pure copper is used in electrical wiring; copper contains only copper atoms. Water in a refill station has the formula H₂O: each molecule has two hydrogen atoms bonded to one oxygen atom. Carbon dioxide, CO₂, is used to carbonate some drinks; each molecule has one carbon atom bonded to two oxygen atoms. Air, however, is not one pure substance: it is a mixture of gases, mainly nitrogen and oxygen, whose particles are not chemically bonded to one another.

4.Classify each: pure copper, water (H₂O), carbon dioxide (CO₂), and air. Use the terms element, compound or mixture.

Pure copper
Water (H₂O)
Carbon dioxide (CO₂)
Air

Compound
Mixture
Element
Compound

5.A label says CO₂. What does the small 2 tell you about each carbon dioxide molecule?

6.A student says, “Air is a compound because nitrogen and oxygen are together.” Identify the mistake and give a more accurate classification.

7.Evie compares one H₂O molecule with one CO₂ molecule. Which statement is correct?

Both are compounds, but they contain different elements and the same total number of atoms.
H₂O is an element and CO₂ is a compound.
Both are mixtures because each has more than one atom.

8.True or false: A substance can be made of molecules and still be an element, if every molecule contains only one type of atom. Use Sample B as evidence.

TrueFalse

9.Complete the sentence: A compound forms when atoms of elements are chemically bonded in a fixed arrangement.

10.Xavier finds a sealed sample containing only identical particles. Each particle has one black atom bonded to three white atoms. Is the sample an element, compound or mixture? Explain using the particle evidence.