Question

Two changes are stated below:
(i) A piece of magnesium gives of bright flames when burnt.
(ii) A piece of iron glows red when heated strongly.

Which of these is a chemical change?

• A. i only
• B. ii only
• C. Both i and ii
• D. None of the above

Answer 1

Answer: (A)

i only

i) When magnesium is burnt, it reacts with the air and gives bright flames and this change cannot be reversed. It is a chemical change. The new product form is Magnesium oxide.

ii) When iron heated strongly it turns red. When heating is stopped it cools and gets back to its original form. So this is a physical change.