Question

A chemist heats liquid bromine to 335 K, and a gas forms. Some properties of bromine are described by data in the table below. (1 point)

Br—Br bond energy (298 K)---------------- 192.807 kJ/mol
Br2 vaporization energy, ΔH°vap--------- 30.91 kJ/mol
Boiling point of bromine---------------------- 332 K

Is the change that occurs a physical change, a chemical change, or both? Support your answer using the data and a discussion of intramolecular and intermolecular forces.

Answer 1

from wiki:

Chemical change is any change that results in the formation of new chemical substances. At the molecular level, chemical change involves making or breaking of bonds between atoms. These changes are chemical: iron rusting (iron oxide forms)

Answer 2

Br—Br bond energy (298 K)---------------- 192.807 kJ/mol
Br2 vaporization energy, ΔH°vap--------- 30.91 kJ/mol
Boiling point of bromine---------------------- 332 K

these data points aren't given for some sparkle and magic, they are there for a reason.

Answer 3

So it takes 192.807 Kj of heat to break down the bond of

Br-Br (this is usually called molar enthalpy of fussion) we are breaking this down from a solid to a liquid.

Then once we are in liquid form, we then need to break down the bonds even further to go from liquid to gas

Answer 4

So first,

we have to break down the bonds Br-Br because this is a solid for, to go from solid to liquid we need "Br—Br bond energy (298 K)---------------- 192.807 kJ/mol" this much energy

Answer 5

second, Solid -> ((((Liquid -> gas))))

now the compound consists of Br2 molecules that are in liquid form. we need Br2 vaporization energy, ΔH°vap--------- 30.91 kJ/mol" energy to go from liquid to gas.

Answer 6

To go from solid to liquid we use molar enthalpy of fusion (Br—Br bond energy (298 K)---------------- 192.807 kJ/mol)

Answer 7

to go from liquid to gas we use molar enthalpy of vaporization (Br2 vaporization energy, ΔH°vap--------- 30.91 kJ/mol)

which is @ Boiling point of bromine---------------------- 332 K"

Answer 8

Now going back to our wiki deffinition of chemical change:

Chemical change is any change that results in the formation of new chemical substances. At the molecular level, chemical change involves making or breaking of bonds between atoms. These changes are chemical: iron rusting (iron oxide forms)

Answer 9

Oh gosh you are really smart

Answer 10

Do you think we are describing this definition with that process?

Answer 11

:P haha

Answer 12

:D well, there are changes in their states but does that mean chemical changes?

Answer 13

Exactly, I'm glad you caught that. Because think of water.

Ice - water - water vapor. Bonds are broken right? Correct, but does that mean it is a chemical change?

Answer 14

True

Answer 15

Going from ice --> water the hydrogen bonds are changing, which is a physical change, however.

Going from water ---> water vapor h2o---> H2 + O2, do you think this is physical or chemical :P?

Answer 16

Is that a trick question? I am now afraid to answer wrong

Answer 17

lmao it is a trick question, because boiling something is always going to result into a physical change, because water vapor and water are the same molecular structure. :P Because no new substance has been formed, think of it that way.

If we were to cool down the gas (water vapor) it would simply turn back to water!!!!

Answer 18

SCIENCE@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
mind blown

Answer 19

lol so this entire explanation is to prove that it's actually a physical change?

Answer 20

yes lol.

Answer 21

haha Omg sweet