In a physical change, like changing state from a solid to a liquid, the substance itself doesn't change. How is a chemical change different from a physical change?

A chemical change is when the substance becomes something new.

Explanation:

Think about it like paint. Your two substances and red and blue. When you mix them together you get purple. It's no longer red paint or blue paint, it's purple paint. That's a chemical change.

as resources become scarce because of population growth, the growth decreases after few years due to lack of resources and food.

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