Year 7 Science · Unit 2 · Lesson 3
Foundation Worksheet
Learning Goals
Match each word to its meaning
Write the letter of the correct meaning next to each word. Each letter is used once.
| Word | Letter | Meaning |
|---|---|---|
| Density | A. A material that blocks heat or electricity | |
| Solubility | B. How much mass is packed into a given volume (mass ÷ volume) | |
| Conductor | C. A feature you can measure without changing the substance | |
| Insulator | D. A material that lets heat or electricity through easily | |
| Physical property | E. How much of a substance can dissolve in a liquid |
True or false? Fix the false ones
Circle T or F. If a statement is false, correct it on the line.
1. An object floats in water if its density is less than 1.0 g/cm³.
Correct it:
2. Ice floats on water because ice is less dense than liquid water.
Correct it:
3. Gold sinks in water because it is a metal.
Correct it:
4. Metals are usually good electrical conductors, but most non-metals are insulators.
Correct it:
5. Sugar dissolves easily in water, so it has low solubility.
Correct it:
1. Power cables have a copper core wrapped in plastic. Explain the job of each material, using the words conductor and insulator.
Odd one out
In each group, circle the item that does not belong. Then explain why, using the property given in brackets. There is one best answer in each group.
| Group | Circle the odd one out | Reason |
|---|---|---|
| 1 | (Electrical conductivity) copper · aluminium · iron · wood | |
| 2 | (Float or sink in water) cork (0.24 g/cm³) · ice (0.92 g/cm³) · wood (0.5 g/cm³) · aluminium (2.70 g/cm³) | |
| 3 | (Solubility in water) table sugar · table salt · beach sand · honey |
2. A wooden block is 5.0 cm long, 4.0 cm wide and 2.0 cm high. Its mass is 20 g. Calculate (a) its volume and (b) its density. (c) Will it float or sink in water?
Density g/cm³
Read the data: a density jar
Scenario
Mia carefully pours honey, water and olive oil into a tall jar and lets them settle into layers. Then she drops in a cork, a plastic bead and a small iron nut.
| Material | Liquid or object? | Density (g/cm³) |
|---|---|---|
| Honey | Liquid | 1.42 |
| Water | Liquid | 1.00 |
| Olive oil | Liquid | 0.92 |
| Cork | Object | 0.24 |
| Plastic bead | Object | 1.2 |
| Iron nut | Object | 7.87 |
Source: values from the lesson.
3. List the three liquids in order from the top of the jar to the bottom. Explain your order.
4. Predict where the cork, the plastic bead and the iron nut end up in the jar. Give a reason from Table 1 for each.
5. In winter, a lake high in the mountains freezes over at the top, not at the bottom. Explain why the ice forms on top, and why this helps the fish and frogs in the lake survive the winter.
Match each word to its meaning
Density → B; Solubility → E; Conductor → D; Insulator → A; Physical property → C.
True or false
1. True. 2. True. 3. False: gold sinks because its density (19.3 g/cm³) is greater than water’s (1.0 g/cm³). 4. True. 5. False: sugar dissolves easily, so it has high solubility.
Question 1
Copper is a conductor, so it carries the electricity (1). Plastic is an insulator, so it stops the electricity reaching you (1). [2 marks]
Odd one out
1. Wood: an insulator; the metals conduct electricity. 2. Aluminium: it sinks (2.70 is more than 1.0); the others float. 3. Beach sand: it does not dissolve in water; the others do. [3 marks]
Question 2
(a) V = 5.0 × 4.0 × 2.0 = 40 cm³ (1). (b) d = 20 ÷ 40 = 0.5 g/cm³ (1). (c) It floats, because 0.5 is less than 1.0 g/cm³ (1). [3 marks]
Read the data: a density jar
3. Olive oil (top), water, honey (bottom) (1). A less dense liquid sits above a denser one (1). [2 marks]
4. Cork floats on top of the oil, because 0.24 is less than 0.92 (1). The bead sinks through the oil and water but floats on the honey, because 1.2 is between 1.00 and 1.42 (1). The iron nut sinks to the bottom, because 7.87 is more than 1.42 (1). [3 marks]
Question 5
Marking guide: 1 ice (0.92 g/cm³) is less dense than water (1.0 g/cm³); 1 when water freezes its particles form a six-sided crystal with large gaps, so ice takes up more space; 1 less dense ice floats, so the lake freezes from the top down; 1 the ice forms a lid that keeps the liquid water below from freezing, so animals live under it; 1 if ice were denser, lakes would freeze from the bottom up and most of the life in them would die. [5 marks]
Model answer: Ice (0.92 g/cm³) is less dense than water (1.0 g/cm³) because its particles form a crystal with large gaps. So ice floats and the lake freezes from the top. The ice is a lid that insulates the liquid water below so it does not freeze, and fish and frogs survive in it. If ice were denser, the lake would freeze from the bottom up, killing most of its life.
Common error: saying something sinks because it is heavy or a metal.