Year 8 Science · Unit 2 · Lesson 18
Foundation Worksheet
Learning Goals
True or false? Fix the false ones
Circle T or F. If a statement is false, correct it on the line.
1. Pure 24-carat gold is the best choice for a ring because it is the hardest form of gold.
Correct it:
2. Copper can be drawn out into a long, thin wire without snapping.
Correct it:
3. Silicon is used in computer chips and solar panels because it is a semiconductor.
Correct it:
4. Diamond and graphite are made of two different kinds of carbon atom.
Correct it:
5. An element that does not react with anything has no useful properties.
Correct it:
Put the copper reasoning chain in order
Number the statements from 1 (the atom) to 5 (the use), so that each one leads to the next.
| Step (1–5) | Statement |
|---|---|
| Like other metals, copper conducts electricity well and is ductile. | |
| Copper is chosen for the wiring inside houses. | |
| This places copper in period 4, group 11 of the periodic table. | |
| A copper atom has 29 protons in its nucleus. | |
| Its position on the table shows that copper is a metal. |
Read the data
| Metal | Relative conductivity | Corrosion | Cost |
|---|---|---|---|
| Iron | 16 | Rusts; rust flakes off | Very low |
| Gold | 72 | Does not corrode | Extremely high |
| Copper | 95 | Corrodes only slowly | Medium |
| Aluminium | 59 | Protected by its oxide layer | Low |
| Silver | 100 | Slowly tarnishes | Very high |
Source: standard conductivity data, rounded (silver = 100); cost is a rough comparison per kilogram.
1. Which metal in Table 1 is the best conductor of electricity? Which is the worst?
2. Silver is the best conductor, yet houses are wired with copper. Use two columns of Table 1 to explain why copper wins over silver, and why it also wins over iron.
Scenario: the school weather balloon
A science club is launching a weather balloon with a small camera attached, with students standing nearby. Hydrogen would give the balloon slightly more lift, but the teacher insists on helium.
3. Explain the teacher’s choice. Use two properties of helium and one property of hydrogen, then name one other job where helium is useful for the same reason.
True or false
1. False: pure gold is so soft a fingernail scratches it; an alloy such as 18-carat gold (with copper and silver) is harder, so it keeps its shape as a ring. 2. True. 3. True. 4. False: both are made of the same carbon atoms; only the arrangement of the atoms differs. 5. False: being unreactive is itself useful, e.g. helium will not burn in a balloon and will not attack an MRI magnet.
Put the copper reasoning chain in order
Reading down the table as printed: 4, 5, 2, 1, 3.
Chain: 29 protons → period 4, group 11 → a metal → conducts well and is ductile → used for house wiring.
Read the data
1. Best: silver (100). Worst: iron (16). [2 marks]
2. Copper conducts almost as well as silver (95 vs 100) but costs far less, so silver is not worth the extra cost. Iron is cheap but conducts poorly (16) and rusts, so a wire sealed in a wall would fail. Copper is the best balance of conductivity, corrosion and cost. [3 marks: 1 silver cost, 1 iron conductivity or rusting, 1 balance of properties]
Show What You Know
3. Marking guide (points expected): 1 helium is much less dense than air (a litre weighs about a sixth to a seventh as much), so the balloon floats; 1 helium is inert, so it cannot burn; 1 hydrogen is lighter but burns fiercely (e.g. the Hindenburg airship fire, 1937), a risk with people nearby, so a little lift is traded for safety; 1 another use relying on helium being unreactive: liquid helium cooling the magnets of an MRI scanner. [4 marks]
Common error to watch for: answering the balloon question with “helium is lighter than hydrogen”. Hydrogen is the lighter gas; helium is chosen because it will not burn.