Question

what is a physical and chemical changes​

Answer 1

Answer:

Physical changes only change the appearance of a substance, not its chemical composition. Chemical changes cause a substance to change into an entirely substance with a new chemical formula. Chemical changes are also known as chemical reactions.

Answer 2

Answer:

Physical Change:

1. A physical change alters the form of a substance but does not change it into another substance.
2. It changes shape or size
3. It dissolves
4. It changes phase (freezes, boils, evaporates, condenses)
5. They occur when matter changes its form but not its chemical nature
6. Most of these changes are reversible
7. Eg. Making orange juice

Chemical Change:

1. Chemical changes are changes matter undergoes when it becomes a new or a different matter.
2. It burns
3. Temperature changes without heating or cooling
4. It bubbles (makes gas)
5. It changes colour
6. It forms a precipitate
7. When a substance undergoes this change, its chemical properties changes
8. To identify chemical change, look for signs like colour change, bubbling and fizzing, light production, smoke, and presence of heat.
9. Most of these changes are irreversible except for the electrolysis of water in which electricity is passed in water to produce hydrogen and oxygen.
10. Eg. Burning of fire crackers.