Year 8 Science · Unit 2 · Lesson 11
Foundation Worksheet
Learning Goals
Fill the gap
Choose the correct word from the word bank. Three words will not be used.
Classroom models of the atom are on purpose. Every model has a , something it shows clearly, and a , something it leaves out or gets wrong. Scientists choose the model that suits their , and they revise a model when new does not fit it.
Put the model cycle in order
These four stages happen again and again in science. Number them from 1 (first) to 4 (last).
| Stage (1–4) | What happens |
|---|---|
| Scientists propose a model to explain what they have seen. | |
| The model is revised or replaced, and testing starts again. | |
| Scientists make observations and carry out experiments. | |
| New evidence is found that the model cannot explain. |
True or false? Fix the false ones
Circle T or F. If a statement is false, correct it on the line.
1. A classroom model can be useful even though it is not to scale.
Correct it:
2. Dalton’s model still shows well that atoms rearrange in chemical reactions.
Correct it:
3. Thomson’s model shows a tiny, dense nucleus at the centre.
Correct it:
4. The quantum model is more accurate than Bohr’s, but its maths makes it harder to use.
Correct it:
5. Two different atomic models can both be useful, for different questions.
Correct it:
Read the data
Scenario: a class vote
25 students voted for the best model for two questions. Q1: How can we show Year 7 that matter is made of tiny particles that rearrange in reactions? Q2: Why do sodium and potassium react in similar ways?
| Question | Dalton | Thomson | Rutherford | Bohr | Quantum |
|---|---|---|---|---|---|
| Q1 | 9 | 2 | 3 | 10 | 1 |
| Q2 | 1 | 2 | 6 | 15 | 1 |
Source: sample class results.
1. For Q2, how many students did not vote for the Bohr model? Show how you worked it out.
Answer students
2. Bohr won both votes. Explain why Bohr suits Q2, but Dalton’s model may be better for Q1.
3. Your textbook draws sodium as a Bohr diagram, with electrons as dots on neat rings. Real electrons do not move on rings. Explain why this diagram is still a good choice for Year 8.
Fill the gap
simplified; strength; limitation; purpose; evidence. Not used (3): newest, colourful, perfect.
Put the model cycle in order
Reading down the table as printed: 2, 4, 1, 3.
True or false
1. True. 2. True. 3. False: Thomson’s model has electrons spread through a positive sphere and no nucleus; Rutherford’s model added the tiny, dense nucleus. 4. True. 5. True.
Read the data
1. 25 − 15 = 10 students. [2 marks: 1 working, 1 answer]
2. Q2: the Bohr model shows electrons in shells, so it shows that sodium and potassium each have one outer-shell electron, which is why they react alike. Q1 only needs atoms as tiny particles that rearrange; Dalton’s spheres show this simply, while Bohr’s shells add detail Year 7 does not need. The best model is the simplest one that answers the question accurately. [3 marks: 1 Bohr and outer electrons, 1 Dalton is enough for Q1, 1 choice depends on the question]
Show What You Know
3. Marking guide (points expected): 1 strength: shows a central nucleus with electrons in shells (such as sodium’s one outer electron); 1 limitation: electrons do not travel on fixed rings, and it is not to scale; 1 the quantum model describes electrons as a cloud and explains their exact behaviour; 1 but its maths is complex, which would hide the simple picture Year 8 needs; 1 a model is judged by whether it suits the question, not by being a perfect copy. [5 marks]
Common error to watch for: in the true or false, marking statement 3 true because “all atomic models have a nucleus”. Thomson’s model came before the nucleus was discovered.