Answer:
Pure Substance. A sample of matter, either a single element or a single compound, that has definite chemical and physical properties. Element. A pure substance that cannot be broken down into other substances by chemical or physical means.
Explanation:
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B. A chemical change has occurred and energy was given off
Answer:
A is denser than B as it's volume for the same mass is smaller.
Explanation:
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In this case, we first need to take into account that the density of each metal A and B is computed by dividing the mass over the volume of each metal which is actually computed by substracting the volume of water from the volume of the water and the solid:

Next, we compute the densities as shown below:

In such a way, A is denser is B as it's volume for the same mass is smaller.
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