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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.
Answer
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Lightweight: Kevlar® has a significantly lower density (1.44 g/cm³) compared to steel (7.85 g/cm³). This means that body armour made from Kevlar® is lighter, allowing greater mobility for the wearer, which is crucial in a defensive situation.
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Higher Relative Strength: Kevlar® has a relative strength of 5 compared to steel's relative strength of 1. This indicates that Kevlar® can absorb more energy without breaking, providing better resistance against impacts such as bullets.
Step 2
(i) Calculate the surface area to volume ratio of this cube of silver.
Answer
The length of one side of the cube is 2 cm.
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Surface Area (A) of a cube = 6 * (side length)² = 6 * (2 cm)² = 24 cm²
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Volume (V) of a cube = (side length)³ = (2 cm)³ = 8 cm³
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Surface Area to Volume Ratio = A / V = 24 cm² / 8 cm³ = 3 cm⁻¹.
Step 3
(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.
Answer
Nanoparticles of silver have a larger surface area to volume ratio compared to larger powder forms. This increased surface area allows for more active sites for reactions to occur, enhancing the catalytic activity. Furthermore, in nanoparticle form, silver can provide more efficient interaction with reactants, leading to an increased rate of reaction due to a higher concentration of available catalyst particles at the surface.