part 2:
1.Physical properties of materials can be changed by exposure to water, heat, light, or by cutting, mixing, and grinding. A. Observable physical properties can be used to classify materials. These physical properties may include solubility, mass, magnetism, and electrical conductivity.

2.Easy, materials and substances become useful if we use them properly and with knowledge of the outcome. Explanation: We make materials that harm the planets because we don't handle them properly, but if we use them properly we can make them more useful and possibly not harmful.

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