This page contains the detailed and easy notes for AQA GCSE Chemistry Atoms Elements and Compounds for revision and understanding Atomic Structure and Mixtures.

Mixtures

1. a) Define Atoms, Elements, Mixtures and Compounds
2. b) Difference between compounds and Mixtures
3. c) Technique to separate mixtures

• Distillation
• Fractional Distillation
• Crystallization
• Chromatography
• Filtration

Atoms

• Smallest particles that makes matter which contains subatomic particles electrons, protons, and neutrons
• They combine to forms elements, compounds and mixtures

Elements

• Substance made up of only one type of atoms.
• There are more than 100 different elements having different properties
• They can be metals, non-metals or semi metals
• Periodic table represents all the known elements in the order of increasing proton number

Mixtures

• Mixtures are the substances made up of two different elements or compounds which are not combined chemically.
• In mixtures the mixed components retain their properties and can be separated by physical means
• eq: Salt and water
• Sand and Water
• Oil and Water

Compounds

• Compounds are the substance which have more than one atom chemically bonded.
• For example CH4 is made up of one carbon and 4 hydogen atom.
• Compounds has a completely different properties than its constituents elements

1. a) Periodic table contains the elements arranged in the order of increasing proton number.
2. b) Elements are arranged in horozontal S Vertical coloumns
3. c) Metals are to the left and no metals are the to the right
4. d) Elements in the same group have same number of electrons in the outermost shell and show similar chemical properties

Chemical Equations

Elements,Compound And Mixture

AQA GCSE C1 Atoms Elements and Compounds Revision Notes

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Balancing Equations

• Law of Conservation of Mass: In a chemical reaction, mass can neither be created nor destroyed so the mass of reactant is always equal to the mass of products.
• If reaction involves gases then the reaction must be carried out in the closed system to prevent the gas from escaping.
• If the gas escapes from reaction mixture the law will not be valid

Separating Mixtures

Filtration

• Solid component can be separated from a liquid using this technique.
• Solution runs off with soluble components and insoluble component like Sand stick to the filter paper as residue.
• The run off is the filtrate which can be water or the solution with the dissolved components

CRYSTALLIZATION or EVAPORATION

• Heating the mixture in an evaporating basin or water bath
• Water will evaporate leaving the crystals of solids behind.
• Solid can then be collected on a filter paper and dried.

DISTILLATION

• It can be used to separate solid and a liquid in which solid is completely soluble in the solvent.
• It can also be used to separate two liquids which are completely miscible in each other and have different boiling points.
• In evaporation solvent is allowed to evaporate leaving solid behind but in distillation solvent is evaporated and the vapours are passed on to the condenser which cools the vapour and collect the solvent in a separate container.
• In case of separation of two liquids, the one with the lower boiling point will evaporate first and will be collected by the condenser.

FRACTIONAL DISTILLATION

• Used to separate two or more liquids with the similar boiling points. Distillation cannot effectively separate two or more liquids with similar boiling points.
• Round botton flask is fitted with tall fractionating coloumns with glass beads which is connected to a condenser.
• The vapours first evaporate into the fractionating column and hit the glass beads
• Lower boiling point liquids will travel high up the column and reach the condenser and gets separated in the separate flask.
• High boiling point liquids hit the glass beads at the bottom, gets condensed and go back to the flask.

CHROMATOGRAPHY

• Components in the mixture are separated on the basis of solubilties of different components of the mixture in a suitable solvent.
• A capillary tube is used to spot the mixture on the chromatography paper.
• The paper is put inside a solvent and the solvent is allowed to run up the chromatography paper.
• The component of the mixture which is more soluble in the solvent will travel greater distance and will leave its mark near the top.
• The component which is less soluble will have a mark near the bottom.

Name the technique used to separate the following

1. a) Sand and Water – Filtration
2. b) Salt and Water — Distillation
3. c) Components of Ink – Chromatography
4. d) Mixture of Crude Oil – Fractional Distillation
5. e) Copper Sulphate Solution – Crystallization

• To separate salt and sand we can dissolve them in water .
• Salt and Water will form a soluble solution with sand in it as insouble solid.
• The solution can then be filtered using filtration.
• The insoluble sand will stick to the filter paper and the filtrate will contain salt and water.
• The salt and water solution can then by evaporated using crystallization
• The water will evaporate leaving salt behind

Disclaimer:

• Compounds-and-Mixtures.-Questions
• Compounds-and-Mixtures.-Answers
• Purity and Separating Mixtures QP
• Purity and Separating Mixtures MS
• Properties of Materials QP
• Properties of Materials MS