Heat flows from water in one container to another. What difference between the two samples of water causes heat to flow?

Difference in temperature

Explanation:

Temperature is the degree of hotness or coldness of a body. The difference in temperature between two bodies enables heat transfer from the hotter body to the colder one. If two bodies are at the same temperature, heat transfer will not occur between them. This why in the vicinity of hot water, a cold water becomes warmer.