WJEC Smart Materials

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A thermochromic substance ...

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Changes colour when the temperature changes.

Answer explanation

A thermochromic substance specifically changes colour in response to temperature variations, making 'Changes colour when the temperature changes' the correct choice. The other options describe different properties.

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A photochromic substance ...

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Changes colour when the light intensity changes.

Answer explanation

A photochromic substance is defined by its ability to change color in response to varying light intensity, making the first choice correct. The other options describe different properties unrelated to photochromism.

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A hydrogel...

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Absorbs up to 1000 x its volume in water.

Answer explanation

Hydrogels are known for their ability to absorb large amounts of water, often up to 1000 times their volume. This property makes them useful in various applications, unlike the other options which do not accurately describe hydrogels.

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A shape memory polymer ...

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Returns to its original shape when heated.

Answer explanation

A shape memory polymer is designed to return to its original shape when heated, demonstrating its unique property of shape memory. This distinguishes it from other materials that may change color or absorb water.

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A shape memory alloy...

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Returns to its original shape when heated.

Answer explanation

A shape memory alloy is designed to return to its original shape when heated, demonstrating its unique property of shape memory. This distinguishes it from other options that do not accurately describe its behavior.

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A shape memory alloy is...

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Metal

Answer explanation

A shape memory alloy is a type of metal that can return to a predetermined shape when heated. Therefore, the correct answer is 'Metal'.

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A shape memory polymer is...

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Plastic

Answer explanation

A shape memory polymer is a type of plastic that can return to a predetermined shape when exposed to certain stimuli, such as heat. Therefore, the correct answer is 'Plastic'.

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A hydrogel is used in...

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Nappies

Answer explanation

A hydrogel is a superabsorbent material commonly used in nappies to absorb moisture and keep the skin dry. It is not typically used in gumshields, glasses frames, or transition lenses.

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A shape memory alloy is used in ... Nappies, Gumshields / mouthguards, Glasses frames, Transition glasses lenses

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Glasses frames

Answer explanation

A shape memory alloy is used in glasses frames because it can return to a predetermined shape when heated, providing flexibility and durability, making them ideal for eyewear.

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A shape memory polymer is used in...

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Gumshields / mouthguards

Answer explanation

A shape memory polymer is ideal for gumshields/mouthguards as it can adapt to the shape of the mouth and provide comfort and protection during sports, making it the correct choice among the options.