Explain why powdered milk and water do not
form a homogeneous mixture​

Milk, which when not subjected to temperature, is a homogeneous mixture. This is because- the various components of pure milk, which are the nutrients present in it, don't form separate layers in it and hence can’t be separated by any physical method.

But when milk is subjected to external factors, such as temperature, the milk fat no more remains dissolved in the milk but instead can be seen as a layer on the top-either as a white solid layer which is called as the cream or as yellow droplets. The two layers can be separated by physical means and hence making milk a heterogeneous mixture.

So the conclusion is that milk is a homogeneous mixture by default.

Explanation:

c. 4.54 x 10–12 j happens to be correct