Question

You are always not to keeps our things like lemon in metal vessels as they become toxic on doing so which type of change is this

Answer 1

we should not keep lemon in a metal vessel because the citric acid present in lemon reacts with the metal to form metallic salt which is toxic.
It is an example of chemical change

Answer 2

You are always not to keep our things like lemon in metal vessels as they become toxic
This is also an example of chemical changes