1. If you blend red and blue, you get purple.
2. Oil won't blend with water.
3. If you blend red with blue, you get purple.
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Can we use 'mix' instead of 'blend' in each sentence? Are bothe the same in meaning? Does #3 mean #1?
Yes to all three of your questions!
Yes, you can use "mix" instead of "blend" in each of these sentences because both words have similar meanings when it comes to combining or combining substances together. Both words imply the action of thoroughly combining or merging different ingredients or substances.
Regarding the meaning, sentences 1 and 3 have the same meaning. They both state that when you combine or blend the colors red and blue, the result is the color purple. Sentence 2, however, is unrelated and discusses the inability of oil and water to mix or blend together due to their different properties and chemical compositions.