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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

what is variations in raman spectra for nanomaterials
Jyoti Reply
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
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
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.
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 did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit 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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