I have a lab to do. In order to complete the lab I need to know this. In my expt. I had to melt wax and then let it form a ball on 3 different wires of 3 different thicknesses to find out which conducts heat faster. Let the wax dry, then, put 1 end of the wire over a fire. During this, I observed all the wires. They all charred after a layer of some copper type coating came off. I was able to wipe it off with my fingures, but i don`t know why that happened.
2007-01-27 05:36:56 · 4 answers · asked by stusa 1 in Science & Mathematics ➔ Chemistry
Metals do not char. A material must have carbon in it to char. In fact the "char" is short for "charcoal."
I am assuming that you are placing the end of the wire into the fire opposite the end with the wax (in order to see how long it takes the heat to melt the wax on the other end).
The black coating you mentioned could be one of several things depending upon the source of the fire that you used.
If the fire was a candle flame, the black coating was soot, which condensed upon the wire which was originally colder than the flame.
If the fire was in the outer cone (the oxidating part of the flame) of a Bunsen burner, it could be the formation of Copper (II) oxide, which is black and easily removed from the wire.
There is another possibility and that is the wire was coated with a thin polymer layer (lacquer used to be used). This layer protects the metal, but contains carbon and does char when heated.
2007-02-03 20:57:16 · answer #1 · answered by Richard 7 · 13⤊ 0⤋
Assuming the copper wires looked like "bare" copper wire, your bare copper wire probably had a layer of clear polymeric coating on it. This would certainly burn and char given its organic and then fall off. This keeps the copper shiny during transport for sale to end users.
Copper will oxidise to black copper oxide in aor if heated to red heat.
2007-01-27 10:19:28 · answer #2 · answered by Anonymous · 0⤊ 0⤋
Yes, meal can char. Char is not a chemistry term. The term you use is oxidize. To test whether the metal charred, use 'clean' heat, like from an electrical burner. Candles, or anything that oxidize fuel, will leave their oxides on the cooler metal.
Since candles do not have a hot flame, you more likely had soot than cupric oxide. If it rubbed off (easily) it was soot. If you had to rub harder or scratch, it could have been cupric oxide.
2007-02-04 01:35:54 · answer #3 · answered by Matthew P 4 · 0⤊ 0⤋
Copper wire will oxidise if heated in air to form black copper oxide on the surface. The oxide layer is usually quite easy to remove, as you've found out.
2Cu + O2 --> 2CuO
2007-01-27 05:52:08 · answer #4 · answered by Gervald F 7 · 0⤊ 0⤋