Question regarding melting points?

Question

Hello, I am a first time poster, and I need to confirm the answers that my older brother gave me for the following questions. thanks

1. The melting point of water is 0 oC. Is water a liquid or a solid at -20 oC? Why?

2. The melting point of fluorine, F2, is -220 oC and the melting point of chlorine, Cl2, is -103 oC. Will the melting point of bromine, Br2, be higher or lower than that of chlorine? Why?

You're right, this is my account's 2nd post, but it's actually MY first post. My friend posted the other question because he didn't have an account. Thanks for the help!!!

Answer 1

1.- Since the melting poinmt of water is Zero Deegres, at any temperature above that point, it is a liquid, up to its boiling point, where it becomes a vapor or gas.
2.- The melting point of F2, flourine is minus 219.61 deg. Celsius, close enough to your data, but the melting point of Cl2, chlorine, is minus 101 deg. C.
The melting point of Bromine, Br2, is minus 7.2 Deg. C

Answer 2

I disagree with all the previous answers before me. Your melting point is lowered likely because your product is still a little wet, likely from water or whatever solvent you used. If it's still wet (even just a little), you'll see it turn into the liquid phase faster than you're supposed to, thus a lower melting melt. That's why they tell you to make sure your product is DRY (by vacuum suction for a while and breaking up the product into a powder) before doing any analysis on it, especially melting/boiling points. It's a simple explanation. As for impure products/byproducts, they might not give you lower melting points, because you may not know what they are and they could have higher melting points than your expected product.

Answer 3

Hi. You are a second time poster. But that's OK. Water is a solid at any temp below 0 deg C at normal pressure. Second question try here : http://environmentalchemistry.com/yogi/periodic/Br.html