Why are told that a sample of matter gives energy as it changes. Can you conclude type of change occurred? Why or not?

1 Answer
Jul 29, 2017

I presume you try to differentiate physical versus chemical change.......


And the answer to your question is......#"absolutely not"#.

Chemical change involves the formation of new substances, and the making and breaking of strong chemical bonds. It can involve enthalpy change. The reaction is either exothermic, releasing energy to the surroundings, or endothermic, absorbing energy from the surroundings.

But physical change, which mostly involves a change of physical state, solid to liquid, liquid to gas, etc. also involves energy exchange with the surroundings, and the energy exchange can likewise be exothermic or endothermic.

The moral....we can make no conclusion with regard to the type of change involved in the exothermic process.