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Chemistry

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I have a couple of questions I need a hand with:

1. Oxygen has a melting point of -218 degrees celcius and a boiling point of -183 degrees celcius. This means that oxygen would be a liquid at...?
Please do not tell me the answer, but tell me the relation between the melting point and boiling point and HOW i can use it to determine when a substance is liquid. Feel free to give me examples.

2. When a substance absorbs heat from its surroundings it could:
A) condense or melt.
B) solidify or condense.
C) evaporate or condense.
D) evaporate or melt.
I'm guessing it is 'evaporate or melt'? Correct me if I am wrong, along with an explanation.

3. When wax melts, the wax particles:
A) change shape to fit the surface they are on.
B) gain energy and spread out alot.
C) become softer.
D) Gain energy and move more freely.
I'm caught between B) and D).. but leaning towards D) more. Again, any explanations would be great!

Thank you very much.

  • Chemistry -

    First, note the correct spelling of celsius.
    It's tough to draw pictures on the board. Here's about the best I can do for #1, oxygen.

    _______25 C room tempeature



    oxygen vapor|
    ............v (I tried to draw an arrow pointing down.)



    _______-183 boiling point

    liquid




    ________-218 melting point

    solid
    Therefore, colder than -218 is solid, between -218 and -183 is liquid, and above -183 is vapor.
    I think if you will draw a diagram something like this for the type question you will always know where you are on the temperature scale.

  • Chemistry -

    2. When a substance ABSORBS heat, it moves UP (from a referencer point BELOW) so a solid could melt, a liquid could vaporize. Your answer is correct.

    3. I don't like any of the answers but your answer is the best listed. There is some truth to A (it does change shape and fits the surface), B(it does gain energy--I don't know about spreading out a lot), C (they do become softer), and D. D is the best overall description and it is general.

  • Chemistry -

    Thanks

  • Chemistry -

    how much energy would be required to change 24.7g of ice to liquid water?the heat of fusion for water is 6.01 kj/mol?

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