Milk turns sour. Is this a chemical or physical change?

1 Answer
Henry W.
Oct 1, 2016

Chemical, as chemicals are change resulting in the formation of new substances.

Explanation:

When milk turns sour, what is actually happening is that bacteria are converting the lactose sugars in milk into energy, with lactic acid as a byproduct. This is a chemical process, as new substances (lactic acid) has been formed

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