Chemistry Igcse

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1) Demonstrate understanding of the terms atom and molecule. Atom= Smallest Unit of Matter
Molecule= 2 or more atoms chemically bonded.
2) Describe paper chromatography.
3) Interpret simple chromatograms.
A method used to separate a Solution, using a Paper and a beaker of water. The Substances in the Paper go up depending on their Mass. We can say that a Solution has the same substance as another solution because they form a line of the same height. 4) Describe methods of separation and purification: filtration, crystallisation, distillation, fractional distillation. Filtration: A way of separating Insoluble Solids from Liquids. With Filter Paper and a Funnel. Crystallisation: Separating Liquids from soluble Solids. Done in Petri dish. Distillation: Separating Liquids depending on their Boiling points.

Fractional Distillation: Same as Distillation but separating more than two Substances with different Boiling Points.

5) Understand the importance of purity in substances in everyday life, e.g. foodstuffs and drugs. If the substances are not pure they can harm you. If they have something toxic within them, if their concentration is too high or too low won’t work as well.

6) Identify substances and assess their purity from melting point and boiling point information. Pure substances have a Boiling and Melting point that is fixed. But when a substance is not pure, the Melting Point goes down and the Boiling point rises. 7) Suggest suitable purification techniques, given information about the substances involved. Purification techniques are the ones mentioned in number 4)

8) Identify physical and chemical changes, and understand the differences between them.

Physical: Physical changes are only of Sate; Gas, Solid or Liquid. Chemical: They are changes that involve a chemical reaction and are not easy to revert.

9) Describe the differences between elements, compounds and mixtures. 10) Demonstrate understanding of the concepts of element, compound and mixture

Elements: A substance made of the same kind of Atom, one type of Atom. Compound: Substances made of different kind of Atoms. A Molecule formed from 2 or more Elements. Mixture: A group of different Substances but are not chemically combined.

11) Describe the structure of an atom in terms of electrons and a nucleus containing protons and neutrons. | Mass| Charge| Location|
Proton | 1| +1| Nucleus|
Electron | 1/2000| -1| Shells|
Neutron| 1| 0| Nucleus|

12) Describe the build-up of electrons in ‘shells’ and understand the significance of the noble gas electronic structures and of valency electrons.

Electrons are distributed in shells, by 2,8, 8. Atoms try to get a complete outer shell to become stable.
Noble Gases: These Elements are in group 8, because they have 8 electrons in the Outer Shell, meaning that they have their shells complete, meaning that they can’t react with another element.
All atoms look for the Nobel Gas Configuration, because it will make them more stable.

13) State the relative charges and approximate relative masses of protons, neutrons and electrons.

See 11)

14) Define proton number and nucleon number.

Nucleon Number = Mass Number = #Protons + #Neutrons
Proton Number = Atomic Number = #Protons = #Electrons

15) Use proton number and the simple structure of atoms to explain the basis of the Periodic Table, with special reference to the elements of proton number 1 to 20.

The Elements in the Periodic table are organised in order of increasing Atomic Number and are also organised in Rows and Columns. Rows named Periods and Columns named Groups. Periods tell us the Number of Shells and Groups tell us the number of Electrons in the Outer Shell.

16) Define isotopes.
Elements with different Atomic Mass. Changes the Neutron number.

17) Use the symbols of the elements to write the formulae of simple...
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