Answer and Explanation: Sample A is a <u>mixture</u>. Solubility is characteristics of each substance, which means a substance can be distinguished from other substances and can be useful to separate mixtures.
In Sample A, when is added different volumes of water, the resulting powder has different mass. This means there are more than one substance forming the yellow cube. Therefore, sample A is a mixture.
Sample B is a <u>pure</u> <u>substance</u>. Each substance has its own melting point. Whe na pure substance reaches its melting point, temperature is constant until all of that substance is melted. In sample B, temperature is stable at 66.2°C and then, after all the powder is melted, it rises again. Therefore, sample B is a pure substance.
I believe the answer is cheamical.
Hope this helps
