States of matter?

Question

a.CH3CH2CH2CH2CH3,boiling point:36'C
b.(CH3)4C,boiling point:10'C
c.CH3CH2OCH2CH3,boiling point:35'C
d.CH3CH2CH2CH2OH,boiling point:117'C
e.(CH3)3COH,boiling point:82'C

by comparing A with B,A with C,Cwith D&Dwith E,suggest explanations for the similarities or differences in the boiling points within each of these 4 pairs.

Guys,i'm kinda confuse..can anyone please explain to me?Really grateful for your explanation and i really appreciate that.Thank you so much!!

Answer 1

A is a linear hydrocarbon and therefore the chains can approach each other resulting in greater overlap than in B which is small and compact like a ball. Thus, A has a higher BP

C has an oxygen atom which causes hydrogen bonding and dipole interations to take place. Thus C has a high BP. However, it is bent at O, which means lesser overlap than A, thus slightly lower BP

D has an -OH group and thus can participate in stronger Hydrogen bonding than C, hence high BP

E again like B, is small and round like a ball, however due to the -OH group it has a high BP but not as high as D

Answer 2

a. liquid
b. gas
c. liquid
d. liquid
e. liquid

To understand states of matter lets look at something familiar first. Lets take water! Room temperature is about 25 'C. Lets say the melting point of water is 0'C. So then, at room temperature water is liquid as its melted. Melting is the transition from solid to liquid which occurs at (usually) 0'C for water. The boiling point of water is 100'C (usually) so we also know that at water room temperature is not a gas. So its not a gas or solid. Its a liquid.


Now lets understand why these compounds have different melting/boiling points. Have you ever held a glass of alcohol? You can smell it far away. Why? Its because the molecules hold on to eachother (intramolecular forces) weakly. And some of the molecules fly into the air. Due to the different levels of these forces some chemicals hold onto eachother strongly and some hold very weakly. Strong holding leads to being solid at high temperatures. Very weak holding leads to being a gas at low temperatures. And there is a whole range of the strength of the forces in between these two extremes.

Now its easy to understand how ionic salts (solids at high temperatures) like rock salt (NaCl/KCl) have strong forces which hold the molecules together. But you might be wondering ... what holds multiple organic (carbon based) molecules together to make liquids and solids? Its all about van der waals forces! And for certain compounds you have some induced dipole moments.
These forces arise because there are electrons involved in bonding between each carbon and the hydrogens attached to it. But the motion of the electrons in one molecule varies to that of the molecule next to it so there is a slight difference in electrical charges between all of the neighboring molecules. The longer the carbon chain the greater these forces are. This explains why compound d has a higher bp than compound e even when theyre both alcohols. When an organic molecule is branched the intermolecular forces are weakened because the surface contact between each molecule is reduced and the weak interactions are reduced. This explains why compound b has a lower bp than compound a. And this is also why compound e has a lower bp than compound d despite the fact that they are both 5 carbon alcohols. There are 3 types of compounds shown above.

1. alkane (compounds:a, b)
2. alcohol (compounds:d,e)
3. ether (compound:c)

1. alkane
Relys purely on these weak interactions. Induced dipole/induced dipole interactions.

2. alcohol
Relys on the weak forces. But because the OH group has such a great difference in electronegativity so there is hydrogen bonding which increases the boiling points.

3. Ether
The forces in an ether are similiar but slightly stronger than those in an alkane. This is due to the oxygen.


Thats it. Good luck.

Answer 3

matter exsist at three states : solid , liquid, gas but at the point of chamistry physics at high temperature gases is ionized and this state is called plasma.

Answer 4

i'm confused also. sorry