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Interesting fact

Normally, healthy kidneys remove waste products from the blood. When a person has renal failure, their kidneys cannot do this any more, and this can be life-threatening. Using dialysis, the blood of the patient flows on one side of a semi-permeable membrane. On the other side there will be a fluid that has no waste products but lots of other important substances such as potassium ions (K + ) that the person will need. Waste products from the blood diffuse from where their concentration is high (i.e. in the person's blood) into the 'clean' fluid on the other side of the membrane. The potassium ions will move in the opposite direction from the fluid into the blood. Through this process, waste products are taken out of the blood so that the person stays healthy.

Investigation : the separation of a salt solution


To demonstrate that a homogeneous salt solution can be separated using physical methods.


glass beaker, salt, water, retort stand, bunsen burner.


  1. Pour a small amount of water (about 20 ml) into a beaker.
  2. Measure a teaspoon of salt and pour this into the water.
  3. Stir until the salt dissolves completely. This is now called a salt solution . This salt solution is a homogeneous mixture.
  4. Place the beaker on a retort stand over a bunsen burner and heat gently. You should increase the heat until the water almost boils.
  5. Watch the beaker until all the water has evaporated. What do you see in the beaker?


The water evaporates from the beaker and tiny grains of salt remain at the bottom. (You may also observe grains of salt on the walls of the beaker.)


The salt solution, which is a homogeneous mixture of salt and water, has been separated using heating and evaporation.

Discussion : separating mixtures

Work in groups of 3-4

Imagine that you have been given a container which holds a mixture of sand, iron filings (small pieces of iron metal), salt and small stones of different sizes. Is this a homogeneous or a heterogeneous mixture? In your group, discuss how you would go about separating this mixture into the four materials that it contains.


  1. Which of the following substances are mixtures ?
    1. tap water
    2. brass (an alloy of copper and zinc)
    3. concrete
    4. aluminium
    5. Coca cola
    6. distilled water
  2. In each of the examples above, say whether the mixture is homogeneous or heterogeneous

Pure substances: elements and compounds

Any material that is not a mixture, is called a pure substance . Pure substances include elements and compounds . It is much more difficult to break down pure substances into their parts, and complex chemical methods are needed to do this.


An element is a chemical substance that can't be divided or changed into other chemical substances by any ordinary chemical means. The smallest unit of an element is the atom .


An element is a substance that cannot be broken down into other substances through chemical means.

There are 112 officially named elements and about 118 known elements. Most of these are natural, but some are man-made. The elements we know are represented in the Periodic Table of the Elements , where each element is abbreviated to a chemical symbol . Examples of elements are magnesium (Mg), hydrogen (H), oxygen (O) and carbon (C). On the Periodic Table you will notice that some of the abbreviations do not seem to match the elements they represent. The element iron, for example, has the chemical formula Fe. This is because the elements were originally given Latin names. Iron has the abbreviation Fe because its Latin name is 'ferrum'. In the same way, sodium's Latin name is 'natrium' (Na) and gold's is 'aurum' (Au).


A compound is a chemical substance that forms when two or more elements combine in a fixed ratio. Water (H 2 O), for example, is a compound that is made up of two hydrogen atoms for every one oxygen atom. Sodium chloride (NaCl) is a compound made up of one sodium atom for every chlorine atom. An important characteristic of a compound is that it has a chemical formula , which describes the ratio in which the atoms of each element in the compound occur.


A substance made up of two or more elements that are joined together in a fixed ratio.

[link] might help you to understand the difference between the terms element , mixture and compound . Iron (Fe) and sulphur (S) are two elements. When they are added together, they form a mixture of iron and sulphur. The iron and sulphur are not joined together. However, if the mixture is heated, a new compound is formed, which is called iron sulphide (FeS). In this compound, the iron and sulphur are joined to each other in a ratio of 1:1. In other words, one atom of iron is joined to one atom of sulphur in the compound iron sulphide.

Understanding the difference between a mixture and a compound

Elements, mixtures and compounds

  1. In the following table, tick whether each of the substances listed is a mixture or a pure substance . If it is a mixture, also say whether it is a homogeneous or heterogeneous mixture.
    Substance Mixture or pure Homogeneous or heterogeneous mixture
    fizzy colddrink
    iron filings
    limestone (CaCO 3 )

  2. In each of the following cases, say whether the substance is an element, a mixture or a compound.
    1. Cu
    2. iron and sulphur
    3. Al
    4. H 2 SO 4
    5. SO 3

Questions & Answers

what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
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what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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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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