in a scientific context, how to talk about reasons and consequences?

Question

I've written down 4 sentences and my thoughts.

1. High temperatures would melt stones .( imaginary situation in the time of speaking)

2. High temperatures will melt stones . ( I have no Idea ! - I don't think it suggests a future event )

3. High temperatures melt stones. ( It is a fact and always happened)

4. High temperatures can melt stones. ( High temperatures are able to melt stones, certainly )

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Questions:

Are my paraphrases right ?

I am always mixing up the correct usage of would and will in the such contexts. What is the difference between 1 and 2 ?

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Additional Info:

In Cambridge Advanced Grammar in Use we can read in the unit 16 and on the page 32 that, we can use will/would to talk about things that are or were always true. Thus, I said in sentence 2 that, "I don't think it suggest a future event"

Regards

Answer 1

I would say that they are pretty close. I would only add a few things. One is that sentence 3 should be

High temperatures melt stones.

The plural "temperatures" matches "melt."

The other is that sentence 2 is essentially part of an implied conditional:

High temperatures will melt stones. (If you expose stones to high temperatures).

Sentences 2 and 3 are quite close in meaning. Indeed, all of these sentences convey the same basic fact (with slight differences).

Note that not all conditionals actually have the conditional mood. Compare, e.g., "If you skip your job you will be fired."