Year 8 Science · Unit 2 · Lesson 16
Foundation Worksheet
Learning Goals
Fill the gap
Choose the correct word from the word bank. Each word is used once at most. Two words will not be used.
A strong comparison uses more than one from the periodic table. Elements in the same tend to have similar chemical properties. To compare how well two elements conduct electricity, the most useful feature is their : metal, metalloid or non-metal. The frame “both … …” lets you give a similarity and a difference in one sentence. In science, a comparison should rest on evidence, not .
True or false? Fix the false ones
Circle T or F. If a statement is false, correct it on the line.
1. Two elements in the same period usually have similar chemical properties.
Correct it:
2. The atomic number of an element is the number of protons in each of its atoms.
Correct it:
3. Adding more facts always makes a comparison stronger, even if they do not help answer the question.
Correct it:
4. Fluorine and iodine are both in Group 17, but fluorine is the more reactive of the two.
Correct it:
5. Saying “sodium and potassium are both metals” is true, but it is a weak comparison.
Correct it:
Read the data
| Element | Atomic number | Group | Period | Category | Conducts? |
|---|---|---|---|---|---|
| Potassium (K) | 19 | 1 | 4 | Metal | Yes |
| Calcium (Ca) | 20 | 2 | 4 | Metal | Yes |
| Bromine (Br) | 35 | 17 | 4 | Non-metal | No |
Source: standard periodic table data.
1. Which feature in Table 1 is the same for all three elements? Give its value.
2. Complete the comparison frame for potassium and bromine using Table 1.
| Part of the frame | Your answer |
|---|---|
| Same: one feature. Different: two features. | |
| Both … but … sentence |
Scenario: Zara’s comparison
Zara’s teacher asks: “Which would be better for carrying electricity in a circuit, calcium or bromine?” Zara writes: “Calcium and bromine are both in Period 4, so they are similar.”
3. Explain why Zara’s answer is weak. Then write a strong comparison of calcium and bromine that uses at least three features from Table 1 and answers the teacher’s question.
Fill the gap
feature; group; category; but; opinion. Not used (2): period, colour.
True or false
1. False: elements in the same group (column) tend to have similar chemical properties; elements in a period can be very different. 2. True. 3. False: only features that help answer the question make a comparison stronger; irrelevant facts weaken it. 4. True. 5. True.
Read the data
1. Period; all three are in Period 4. [2 marks: 1 feature, 1 value]
2. Same: Period 4. Different (any two): group (1 and 17); atomic number (19 and 35); category (metal and non-metal); conductivity (yes and no). Sentence, for example: “Potassium and bromine are both in Period 4, but potassium is a Group 1 metal that conducts electricity and bromine is a Group 17 non-metal that does not.” [3 marks: 1 same, 1 two differences, 1 sentence with both … but]
Show What You Know
3. Marking guide (points expected): 1 sharing a period does not make elements similar (similar properties go with the same group), so Zara’s conclusion is wrong; 1 her answer uses one feature and does not answer the question about electricity; 1 at least three features used correctly (for example group 2 and 17, atomic number 20 and 35, metal and non-metal, conducts or not); 1 category identified as the most useful feature for conductivity; 1 clear answer in a both … but sentence, for example “Calcium and bromine are both in Period 4, but calcium is a Group 2 metal that conducts electricity and bromine is a Group 17 non-metal that does not, so calcium is better for carrying electricity.” [5 marks]
Common error to watch for: treating “same period” as “similar”. Remind students that similarity goes with a shared group; a period runs from reactive metals on the left to non-metals on the right.