This question is about properties of materials. Figure 6 shows some properties of steel and Kevlar®: | property | steel | Kevlar® | |--------------------|-------|---------| | density / g cm⁻³ | 7.85 | 1.44 | | relative strength | 1 | 5 | | flexibility | low | high | (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. 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.

GCSE Edexcel Chemistry Combined Science Factors that Affect the Rate of Reaction: This question is about propertie

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

Question 7

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

Step 1

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, we need to first determine the surface area and the volume of the cube:

Surface Area: The formula for the surface area (SA) of a cube is given by:

$SA = 6a^2$

where a is the length of one side. For this cube, a = 2 cm:

$SA = 6(2^2) = 6(4) = 24 ext{ cm}^2$
Volume: The formula for the volume (V) of a cube is:

$V = a^3$

Using the same side length:

$V = 2^3 = 8 ext{ cm}^3$
Surface Area to Volume Ratio: Finally, the surface area to volume ratio (SA:V) is calculated as follows:

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

Thus, the surface area to volume ratio is 3 cm⁻¹.

Step 2

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 silver is used as nanoparticles, it has a significantly higher surface area to volume ratio compared to its powdered form. This increased surface area allows more active sites for catalytic reactions to occur.

With nanoparticles:

The number of particles is larger compared to a bulk form, leading to a higher surface area available for reactions.
There is better accessibility for reactants to reach the catalytic sites.

In contrast, powdered silver has fewer active sites exposed, which results in a lower rate of reaction due to decreased collision frequency between reactants and the catalyst. Therefore, utilizing silver in nanoparticle form enhances its effectiveness as a catalyst.

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

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

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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