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The kinetic theory of matter

The kinetic theory of matter helps us to explain why matter exists in different phases (i.e. solid, liquid and gas), and how matter can change from one phase to the next. The kinetic theory of matter also helpsus to understand other properties of matter. It is important to realise that what we will go on to describe is only a theory . It cannot be proved beyond doubt, but the fact that it helps us to explain our observations of changes in phase, and otherproperties of matter, suggests that it probably is more than just a theory.

Broadly, the Kinetic Theory of Matter says that:

  • Matter is made up of particles that are constantly moving.
  • All particles have energy , but the energy varies depending on whether the substance is a solid, liquid or gas. Solid particles have the least amount ofenergy and gas particles have the greatest amount of energy.
  • The temperature of a substance is a measure of the average kinetic energy of the particles.
  • A change in phase may occur when the energy of the particles is changed.
  • There are spaces between the particles of matter.
  • There are attractive forces between particles and these become stronger as the particles move closer together. These attractive forces will either be intramolecularforces (if the particles are atoms) or intermolecular forces (if the particles are molecules). When the particles are extremely close, repulsive forces startto act.

[link] summarises the characteristics of the particles that are in each phase of matter.

Table summarising the general features of solids, liquids and gases.
Property of matter Solid Liquid Gas
Particles Atoms or molecules Atoms or molecules Atoms or molecules
Energy and movement of particles Low energy - particles vibrate around a fixed point Particles have less energy than in the gas phase Particles have high energy and are constantly moving
Spaces between particles Very little space between particles. Particles are tightly packed together Smaller spaces than in gases, but larger spaces than in solids Large spaces because of high energy
Attractive forces between particles Very strong forces. Solids have a fixed volume. Stronger forces than in gas. Liquids can be poured. Weak forces because of the large distance between particles
Changes in phase Solids become liquids if their temperature is increased. In some cases a solid may become a gas if the temperature is increased. A liquid becomes a gas if its temperature is increased. It becomes a solid if its temperature decreases. In general a gas becomes a liquid when it is cooled. (In a few cases a gas becomes a solid when cooled). Particles have less energy andtherefore move closer together so that the attractive forces become stronger, and the gas becomes a liquid (or a solid.)

The following presentation is a brief summary of the above. Try to fill in the blank spaces before clicking onto the next slide.

Let's look at an example that involves the three phases of water: ice (solid), water (liquid) and water vapour(gas). Note that in the [link] below the molecules in the solid phase are represented by single spheres, but they wouldin reality look like the molecules in the liquid and gas phase. Sometimes we represent molecules as single spheres in the solid phase to emphasise the smallamount of space between them and to make the drawing simpler.

The three phases of matter

Taking water as an example we find that in the solid phase the water molecules have very little energy and can't move away from eachother. The molecules are held closely together in a regular pattern called a lattice . If the ice is heated, the energy of the molecules increases. This means that some of the water molecules are ableto overcome the intermolecular forces that are holding them together, and the molecules move further apart to form liquid water . This is why liquid water is able to flow, because the molecules are more free to move than they were in the solid lattice. If themolecules are heated further, the liquid water will become water vapour, which is a gas. Gas particles have lots of energy and are far away from each other.That is why it is difficult to keep a gas in a specific area! The attractive forces between the particles are very weak and they are only loosely heldtogether. [link] shows the changes in phase that may occur in matter, and the names that describe these processes.

Changes in phase

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
ya I also want to know the raman spectra
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
yes that's correct
I think
Nasa has use it in the 60's, copper as water purification in the moon travel.
nanocopper obvius
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
analytical skills graphene is prepared to kill any type viruses .
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
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Source:  OpenStax, Siyavula textbooks: grade 10 physical science. OpenStax CNX. Aug 29, 2011 Download for free at http://cnx.org/content/col11245/1.3
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