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Natural sciences

Matter, measuring and reactions

Educator section



  • H 2 O
  • Hydrogen and oxygen
  • The elements oxygen and hydrogen joined. This formed a new substance, namely water, that consists of two types of atoms. The atoms joined to form a water molecule.
  • Yes, the elements are combined in a fixed relation to form a new substance with new characteristics.

Assignment 2:


  • 500 oxygen atoms
  • 1 000 oxygen atoms

2. Combination

O 2 Oxygen molecule: two oxygen atoms
NaCl Sodium chloride (table salt): one atom sodium and one atom chloride
N 2 O 5 Sodium oxide molecule: two sodium atoms combine with five oxygen atoms
Fe 2 O 3 Iron oxide: two iron atoms combine with three oxygen atoms
MgCl 2 Magnesium chloride: one magnesium atom combines with two chloride atoms
CO Carbon monoxide: one carbon atom binds to one oxygen atom

Leaner section


Activity: to describe the composition of substances in terms of chemical symbols and formulas [lo 2.3]

When we know the physical and chemical properties of a substance we can use our knowledge to create another substance. Water, a compound, is the best solvent because many substances can dissolve in water. We can use the compound water to obtain gases like hydrogen and oxygen. We can also produce water by mixing these gases.

We make use of chemical symbols to identify elements and use chemical formulas to identify compounds. Here are some chemical symbols:

  • Ag (symbol) is used for silver
  • Fe is used for iron
  • Pb is used for lead
  • Au is used for gold

Try to illustrate the composition of a water molecule:

  • Write the chemical formula for water.


  • Name the two elements that form water?

__________________________________ and _______________________________

  • What had to happen to these elements to form water?

Use the words: elements, atoms and molecules in your explanation.



  • Would this compound depend on a fixed ratio or could it change at random? Motivate your answer.




  • Provide a graphic representation of the atomic composition of water:

Assignment 2

Now try to analyse the chemical formula for carbon dioxide (carbonic acid gas):

Carbon dioxide is a compound of two kinds of atoms. The chemical formula is:


CO 2

This formula signifies that one atom of carbon combines with two atoms of oxygen to form carbon dioxide. We can therefore say that the ratio of carbon atoms to oxygen atoms in carbon dioxide molecules is 1:2.

1. How many atoms of oxygen will have to be present for:

  • 250 carbon atoms?__________________________________________________
  • 500 carbon atoms?__________________________________________________

2. Work out the combinations that are present in the following formulas:

O 2 ____________________________________________________
NaCl ____________________________________________________
N 2 O 5 ____________________________________________________
Fe 2 O 3 ____________________________________________________
MgCl 2 ____________________________________________________
CO ____________________________________________________


Learning Outcome 2: The learner will know and be able to interpret and apply scientific, technological and environmental knowledge.

Assessment Standard 2.3: We know this when the learner interprets information by identifying key ideas in text, finding patterns in recorded data, and making inferences from information in various forms (e.g. pictures, diagrams, text).

Questions & Answers

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.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
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
there is no specific books for beginners but there is book called principle of nanotechnology
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?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
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
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
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Source:  OpenStax, Natural sciences grade 7. OpenStax CNX. Sep 16, 2009 Download for free at http://cnx.org/content/col11077/1.1
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