This question is about properties of materials. (a) Figure 6 shows some properties of steel and Kevlar®. Body armour, such as a bullet-proof vest, could be manufactured using either of these materials. Explain two reasons why Kevlar® is preferred to steel as the material for body armour. (4) (b) The use of nanoparticles has increased in recent years. (i) The length of one side of a cube of silver is 2 cm as shown in Figure 7. Calculate the surface area to volume ratio of this cube of silver. (3) surface area to volume ratio = (ii) Suggest an explanation of why a given mass of silver is more effective as a catalyst when used as nanoparticles rather than in a powder form. (3)

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This question is about properties of materials - Edexcel - GCSE Chemistry - Question 7 - 2016 - Paper 1

Question 7

This question is about properties of materials. (a) Figure 6 shows some properties of steel and Kevlar®. Body armour, such as a bullet-proof vest, could be manufac... show full transcript

Worked Solution & Example Answer:This question is about properties of materials - Edexcel - GCSE Chemistry - Question 7 - 2016 - Paper 1

Step 1

Explain two reasons why Kevlar® is preferred to steel as the material for body armour.

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Answer

Higher Relative Strength: Kevlar has a higher relative strength compared to steel. This means that, for the same weight, Kevlar can provide better protection as it can absorb more energy from impacts without breaking.
Lightweight: With a much lower density than steel, Kevlar is lighter. This makes it more comfortable for wearers of body armour as it reduces fatigue during use.

Step 2

Calculate the surface area to volume ratio of this cube of silver.

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Answer

To calculate the surface area to volume ratio of the cube:

Surface Area (SA): A cube has 6 faces, so the surface area is calculated as:

$SA = 6 imes (side^2) = 6 imes (2 ext{ cm})^2 = 6 imes 4 ext{ cm}^2 = 24 ext{ cm}^2$

Volume (V): The volume of the cube is:

$V = (side^3) = (2 ext{ cm})^3 = 8 ext{ cm}^3$

Surface Area to Volume Ratio:

$ext{Ratio} = \frac{SA}{V} = \frac{24 ext{ cm}^2}{8 ext{ cm}^3} = 3 ext{ cm}^{-1}$

Step 3

Suggest an explanation of why a given mass of silver is more effective as a catalyst when used as nanoparticles rather than in a powder form.

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Answer

When using silver as nanoparticles, it has a much larger surface area compared to an equivalent mass in powder form. This increased surface area allows for more active sites for chemical reactions, resulting in a higher reaction rate. Additionally, nanoparticles have a greater proportion of their atoms on the surface compared to bulk material, making them more effective in catalyzing reactions.

This question is about properties of materials - Edexcel - GCSE Chemistry - Question 7 - 2016 - Paper 1

Worked Solution & Example Answer:This question is about properties of materials - Edexcel - GCSE Chemistry - Question 7 - 2016 - Paper 1

Explain two reasons why Kevlar® is preferred to steel as the material for body armour.

Calculate the surface area to volume ratio of this cube of silver.

Suggest an explanation of why a given mass of silver is more effective as a catalyst when used as nanoparticles rather than in a powder form.

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