How is #"chemical change"# differentiated from #"physical change"#?

2 Answers
Apr 17, 2017

Answer:

Physical change: the identity of the substance(s) doesn't change

Chemical change: the substance reacts and forms (a) new substance(s), cannot be changed back easily, heat or energy is often released/absorbed (exothermic vs. endothermic reactions), a precipitate may form

Basically, you KNOW a chemical change has occurred if you do not change the temperature/heat/energy around a substance, and a change still occurs. If you change the heat/temperature/energy around a substance and a change occurs, then it's considered to be a physical change.

Explanation:

Quiz: (answers below)

  1. Dropping a glass
  2. Burning toast
  3. Wood expanding in the summer
  4. Melting butter for popcorn
  5. Spoiling food
  6. Fireworks exploding
  7. Bleaching your hair
  8. Cooking an egg
  9. Cream being whipped
  10. Mixing lemon powder with water to make lemonade

Note: if this is still unclear, please tell me and I'll try my best to help!

Answers: P, C, P, P, C, C, C, C, P, P

Apr 24, 2017

Answer:

Chemical change is characterized by the formation of new substances, and the making and breaking of chemical bonds.....

Explanation:

Physical changes are largely changes of state, solid to liquid to gas, etc. in which the phase of the substance changes but not its chemical identity.