# 2.2 The properties of matter

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## The properties of matter

Let us now look at what we have learned about chemical bonds, intermolecular forces and the kinetic theory of matter, and see whetherthis can help us to understand some of the macroscopic properties of materials.

1. Melting point
Melting point
The temperature at which a solid changes its phase or state to become a liquid . The process is called melting and the reverse process (change in phase from liquidto solid) is called freezing .
In order for a solid to melt, the energy of the particles must increase enough to overcome the bonds that are holding the particlestogether. It makes sense then that a solid which is held together by strong bonds will have a higher melting point than one where the bonds are weak, because more energy (heat) is needed to breakthe bonds. In the examples we have looked at metals, ionic solids and some atomic lattices (e.g. diamond) have high melting points, whereas the meltingpoints for molecular solids and other atomic lattices (e.g. graphite) are much lower. Generally, the intermolecular forces between molecular solids are weaker than those between ionic and metallic solids.
2. Boiling point
Boiling point
The temperature at which a liquid changes its phase to become a gas . The process is called evaporation and the reverse process is called condensation
When the temperature of a liquid increases, the average kinetic energy of the particles also increases and they are able to overcomethe bonding forces that are holding them in the liquid. When boiling point is reached, evaporation takes place and some particles in the liquid become a gas. In other words, the energy of theparticles is too great for them to be held in a liquid anymore. The stronger the bonds within a liquid, the higher the boiling point needs to be in order tobreak these bonds. Metallic and ionic compounds have high boiling points while the boiling point for molecular liquids is lower.The data in [link] below may help you to understand some of the concepts we have explained. Not all of the substances in the table aresolids at room temperature, so for now, let's just focus on the boiling points for each of these substances. What do you notice?
 Substance Melting point ( ${}^{0}C$ ) Boiling point ( ${}^{0}C$ ) Ethanol (C 2 H 6 O) - 114,3 78,4 Water 0 100 Mercury -38,83 356,73 Sodium chloride 801 1465
You will have seen that substances such as ethanol, with relatively weak intermolecular forces, have the lowest boiling point, while substances withstronger intermolecular forces such as sodium chloride and mercury, must be heated much more if the particles are to have enough energy to overcome theforces that are holding them together in the liquid.

## Forces and boiling point

The table below gives the molecular formula and the boiling point for a number of organic compounds called alkanes (more on these compounds in grade 12). Refer to the table and then answer the questions that follow.

 Organic compound Molecular formula Boiling point ( ${}^{0}$ C) Methane CH 4 -161.6 Ethane C 2 H 6 - 88.6 Propane C 3 H 8 -45 Butane C 4 H 10 -0.5 Pentane C 5 H 12 36.1 Hexane C 6 H 14 69 Heptane C 7 H 16 98.42 Octane C 8 H 18 125.52

#### Questions & Answers

can someone help me with some logarithmic and exponential equations.
sure. what is your question?
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
I don't understand what the A with approx sign and the boxed x mean
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
Salomon
I'm not sure why it wrote it the other way
Salomon
I got X =-6
Salomon
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
oops. ignore that.
so you not have an equal sign anywhere in the original equation?
Commplementary angles
hello
Sherica
im all ears I need to learn
Sherica
right! what he said ⤴⤴⤴
Tamia
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
a perfect square v²+2v+_
kkk nice
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
or infinite solutions?
Kim
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Al
y=10×
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
rolling four fair dice and getting an even number an all four dice
Kristine 2*2*2=8
Differences Between Laspeyres and Paasche Indices
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
is it 3×y ?
J, combine like terms 7x-4y
im not good at math so would this help me
yes
Asali
I'm not good at math so would you help me
Samantha
what is the problem that i will help you to self with?
Asali
how do you translate this in Algebraic Expressions
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
what's the easiest and fastest way to the synthesize AgNP?
China
Cied
types of nano material
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
what is nanomaterials​ and their applications of sensors.
what is nano technology
what is system testing?
preparation of nanomaterial
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
what is system testing
what is the application of nanotechnology?
Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
can nanotechnology change the direction of the face of the world
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
how did you get the value of 2000N.What calculations are needed to arrive at it
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