KS3 Science Homework Pack 2, Homework 6 (continued) - page 13, with questions on element properties, a substance comparison table, and element-property matching exercise.

Here are the solutions to the homework questions.

Question 3

a) Magnesium is a metal. Give two properties of magnesium from the list above.
Metals generally conduct electricity and heat well, have high melting points, and are often magnetic (though not always). Looking at the list:
1. Good electrical conductor
2. Good thermal conductor
*(Other acceptable answers: Melting point above room temperature, Magnetic)*

b) Krypton is a gas used inside a light bulb. Give two properties of krypton from the list above which make it a good material to use.
Krypton is a noble gas. It doesn't react with the filament, and being a gas, it has a very low boiling point. It also does not conduct electricity well (otherwise the current would jump across the bulb instead of going through the filament).
1. Electrical insulator
2. Boiling point -153°C (This shows it is a gas at room temperature)
*(Note: "Poor thermal conductor" is also a valid property for gases).*

c) Tungsten is used to make the filament inside a light bulb. Give two properties from the list above which make it a good material to use.
The filament gets extremely hot when electricity passes through it. Therefore, it must not melt. It also needs to conduct the electricity.
1. Good electrical conductor
2. Melting point 3422°C (It needs a very high melting point so it doesn't melt when glowing white-hot).

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Question 4

Complete the last column on the table by stating whether the substance is a metal, a non-metal or a compound.

* Substance A: It has a low melting point ($113^\circ\text{C}$), is a poor conductor, and burns to form an acidic gas. These are classic properties of a Non-metal (specifically, this looks like Sulphur).
* Substance B: It has a high melting point ($962^\circ\text{C}$), conducts electricity very well, and loses its shiny surface (oxidizes) when heated. These are properties of a Metal.
* Substance C: It has a very low melting point ($-182^\circ\text{C}$), is a poor conductor, and burns to form *two new substances*. When a substance breaks down or reacts to form multiple new things, it indicates it was made of different elements bonded together. This is a Compound.

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Question 5

Rule a line to link the elements to show whether they are metals or non-metals and another line to show one of their properties.

Here is the correct matching logic:

1. Carbon: Is a Non-metal. Property: Brittle (Solid non-metals break easily).
2. Mercury: Is a Metal. Property: Shiny liquid (It is the only metal that is liquid at room temperature).
3. Nickel: Is a Metal. Property: Magnetic (Nickel, Iron, and Cobalt are magnetic metals).
4. Sulphur: Is a Non-metal. Property: Brittle (Like carbon, solid sulphur crumbles). *Note: In these tests, usually "Brittle" links to the solid non-metals.*
5. Copper: Is a Metal. Property: Very good conductor of heat (Copper is used in pots and pans for this reason).

*Self-Correction on Matching:*
Let's look at the specific options provided in the columns to ensure unique pairs where possible, although properties can overlap.
- Carbon $\rightarrow$ Non-metal $\rightarrow$ Brittle
- Mercury $\rightarrow$ Metal $\rightarrow$ Shiny liquid
- Nickel $\rightarrow$ Metal $\rightarrow$ Magnetic
- Sulphur $\rightarrow$ Non-metal $\rightarrow$ Brittle (Both Carbon and Sulphur fit here, but let's see if there is a better fit for Carbon? No, Brittle is the best fit for solid non-metals here).
- Copper $\rightarrow$ Metal $\rightarrow$ Very good conductor of heat (or Conductor of electricity).

Let's refine the lines based on standard KS3 science associations:
- Carbon: Non-metal — Brittle
- Mercury: Metal — Shiny liquid
- Nickel: Metal — Magnetic
- Sulphur: Non-metal — Brittle (Note: If you must pick unique properties, sometimes Sulphur is associated with being yellow/powder, but "Brittle" is the physical property listed. Both Carbon and Sulphur are brittle non-metals).
- Copper: Metal — Very good conductor of heat (Copper is famous for heat conduction).

*Alternative Check:*
Could Carbon be linked to something else? No.
Could Sulphur be linked to something else? No.
So, both Carbon and Sulphur link to "Non-metal" and "Brittle".
Copper links to "Metal" and "Very good conductor of heat" (or electricity).
Nickel links to "Metal" and "Magnetic".
Mercury links to "Metal" and "Shiny liquid".

Final Answer:

3a)
1. Good electrical conductor
2. Good thermal conductor

3b)
1. Electrical insulator
2. Boiling point -153°C

3c)
1. Good electrical conductor
2. Melting point 3422°C

4)
* Substance A: Non-metal
* Substance B: Metal
* Substance C: Compound

5)
* Carbon $\rightarrow$ Non-metal $\rightarrow$ Brittle
* Mercury $\rightarrow$ Metal $\rightarrow$ Shiny liquid
* Nickel $\rightarrow$ Metal $\rightarrow$ Magnetic
* Sulphur $\rightarrow$ Non-metal $\rightarrow$ Brittle
* Copper $\rightarrow$ Metal $\rightarrow$ Very good conductor of heat