Year 8 Science · Unit 2 · Lesson 1
Foundation Worksheet
Learning Goals
Fill the gap
Choose the correct word from the word bank. Two words will not be used.
Anything that has mass and takes up space is called . It is all made of tiny moving . A pure substance made of only one type of atom is an . Two or more elements chemically bonded in fixed proportions make a . Substances that are mixed together but not bonded make a . The smallest unit of an element that still has the properties of that element is an .
True or false? Fix the false ones
Circle T or F. If a statement is false, correct it on the line.
1. The particles in a solid vibrate about fixed positions.
Correct it:
2. In a gas, the particles are packed tightly together.
Correct it:
3. A mixture can be separated by physical means, such as filtering or evaporating.
Correct it:
4. Atoms are far too small to see with our eyes, but scientists have made images of single atoms.
Correct it:
5. Salty water is a compound, because the salt and the water are chemically bonded to each other.
Correct it:
Sort it
Write each substance in the correct box. Each box gets exactly three.
Element
Compound
Mixture
Zoom in: put the pictures in order
Number these from 1 (biggest, what you start with) to 4 (smallest). Then write Yes or No: is it pure iron?
| Order (1–4) | What you have | Pure iron? (Yes or No) |
|---|---|---|
| Protons, neutrons and electrons from a split iron atom | ||
| A bar of iron made from the ore | ||
| A chunk of iron ore rock dug from a mine | ||
| One iron atom |
Scenario: a heated rod
A class clamped an aluminium rod that was exactly 1000.0 mm long at room temperature. They heated it in steps and measured its length each time.
| Temperature (°C) | Length of rod (mm) |
|---|---|
| 20 | 1000.0 |
| 40 | 1000.5 |
| 60 | 1000.9 |
| 80 | 1001.4 |
| 100 | 1001.8 |
Source: sample class results.
1. How much longer was the rod at 100 °C than at 20 °C? Describe the pattern in one sentence.
2. Use the particle model to explain why the rod got longer when it was heated. Jo says: “Every aluminium particle grew bigger.” Is Jo right?
3. Mia drops a sugar cube into a glass of water and stirs. After a minute she cannot see the sugar, but the water tastes sweet. Use the particle model to explain what happened to the sugar. Then say whether the sweet water is an element, a compound or a mixture, and give a reason.
Fill the gap
matter; particles; element; compound; mixture; atom. Not used: proton, energy.
True or false
1. True. 2. False: in a gas the particles are far apart and move freely in all directions. 3. True. 4. True. 5. False: salty water is a mixture; the salt and water are not bonded to each other, and the water can be evaporated off to leave the salt.
Sort it
Element: copper wire, helium gas, diamond (pure carbon). Compound: water, carbon dioxide, table salt (sodium chloride). Mixture: air, sugar dissolved in water, sand stirred into iron filings.
Zoom in: put the pictures in order
Reading down the table as printed: 4, 2, 1, 3.
Pure iron? Protons, neutrons and electrons: No (the pieces are no longer iron). Bar of iron: Yes. Iron ore rock: No (the iron is in compounds mixed with rock). One iron atom: Yes (the smallest unit that is still iron).
Go Deeper
1. 1001.8 − 1000.0 = 1.8 mm. The hotter the rod, the longer it gets, by about 0.4 to 0.5 mm for every 20 °C. [2 marks: 1 value, 1 pattern]
2. Heating makes the aluminium particles vibrate faster, so on average they sit a little further apart; the gaps between them grow, so the whole rod gets slightly longer. Jo is wrong: the particles themselves do not change size. [3 marks: 1 vibrate faster; 1 further apart (bigger gaps between particles); 1 particles do not grow]
Show What You Know
3. Marking guide: 1 the sugar has not disappeared; it has broken up into separate sugar particles too small to see; 1 the water particles are always moving, and they bump the sugar particles and spread them evenly through the water; 1 the sweet water is a mixture; 1 reason: the sugar and water are not chemically bonded, each keeps its own properties (the sugar still tastes sweet), and the water could be evaporated to get the sugar back. [4 marks]
Common error to watch for: saying the sugar “turned into water” or “melted”. It dissolved; the sugar particles are still there, which is why the water tastes sweet.