Physical and Chemical Change

2. Yes, it is still the same substance, H2O. Yes, the physical properties have changed. Physical properties can be observed and measured. Here, they include density, state of matter (phase), etc.Yes, it is still the same substance, H2O. Yes, the physical properties have changed. Physical properties can be observed and measured. Here, they include density, state of matter (phase), etc.

3. Yes, water can go back to being ice in a phase change. Yes, water can go back to being ice in a phase change.

4. No, the paraffin and oxygen have become water and carbon dioxide. Yes, the physical properties have changed. Paraffin is solid and “waxy” and oxygen is a gas molecule. After the reaction, they become two gases. No, the paraffin and oxygen have become water and carbon dioxide. Yes, the physical properties have changed. Paraffin is solid and “waxy” and oxygen is a gas molecule. After the reaction, they become two gases.

5. The obvious answer is “no.”The obvious answer is “no.”

19. Something with a positive charge has to keep the negative charges from “flying off.” Something with a positive charge has to keep the negative charges from “flying off.”