Atoms, Molecules and Compounds

Atoms have positively charged nucleus and electrons which are negatively charged

Atoms can form bonds to make molecules or compounds

Sometimes an atom loads or gains more electrons which gives it a charge (positive if it loses an electron, negative if it gains one)

Fomulas to remember:

  • Calcium chloride: CaCl2
  • Magnesium chloride: MgCl2
  • Sodium carbonate: Na2CO3
  • Calcium carbonate: CaCO3
  • Sulfuric acid: H2SO4
  • Magnesium sulfate: MgSO4
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Additives are added to food to improve their flavour, colour or to make them last longer

Emulsifiers help oil and water mix, mixing an oil with water makes an emulsion

Emulsions-lots of droplets of one liquid suspended in another, oil and water naturally seperate


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Cooking and Chemical Change

Foods are cooked for different reasons:

  • Better taste and texture
  • Easier to digest
  • Kiss microbes
  • Some foods are poisonous when raw

Eggs are meat contain protein, when they're cooked the protein molecule changes shape which gives the food a more edible texture-denaturing

Potatoes are plants so they have a cellulose which human can't digest, cooking ruptures the cell walls so the potato is edible

Baking powder goes under thermal decomposition when heated:
sodium hydrogencarbonate --> sodium carbonate+carbon dioxide+water

2NaHCO3 --> Na2CO3 + CO2 + H2O 

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Esters are used in perfumes and air fresheners as they smell nice

They are found in natural things like fruit and flowers however they can be manufactured synthetically- heating carboxylic acid with an alcohol (esterification)

Acid + Alcohol --> Ester + Water

Perfumes need to:

  • Easily evaporate
  • Non-toxic
  • Doesn't react with water
  • Doesn't irritate skin
  • Insoluble in water
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Forces between particles and kinetic theory

Solids-strong forces of attraction, fixed position, vibrate

Liquids-some force of attraction, free to move past eac other, flow to fill bottom of container, constantly move with random motion

Gases-no force of attraction, only interract when they collide, don't keep any shape will always fill any container, move constantly with random motion, hotter they are more they move

When a liquid is heated the heat energy foes makes particles move faster, some move faster than others, fast moving particles at top will overcome forces of attraction and escape (evaporation)
How easily a liquid evaporates is called its volatility 

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Solution-mixture of solvent and solute

When you add a solid (solute) to a liquid (solvent) the bonds holding the solute molecules sometimes break and the molecules mix to form a solution

Solution-mixture of solute and a solvent that doesn't seperate out

Solute-substance being dissolved

Solvent-liquid it's dissolving into

Soluble-means it will dissolve

Insoluble-means it will NOT dissolve

Solubility-a measure of how much will dissolve

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Paints and Pigments

Paint usually contains: solvent, binding medium and pigment

Pigments-give paints their colour

Binding medium-carries the pigment and holds them together, sticks liquid to surface

Solvent-thins the paint to make it spread easier

Paint-colloid-really tiny particles of one kind of stuff dispersed in another kind of stuff
Colloids don't seperate out because they're so small, paint=paticles of pigment dispersed in liquid

Emulsion-water based paint, solvent and binding medium is acrylic or vinyl acetate polymer
Dries when solvent evaporates, leaves binder and pigment as thin solid film-dries quickly
Don't produce harmful fumes

Gloss-oil based paints, binding material is oil and solvent is organic compound that'll dissolve in oil
Drys in two stages, solvent evaporates then oil is ocidised by oxygen
Oil paints are glossy, waterproof and hard wearing, produce harmful fumes 


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Special Pigments

Thermochromic pigment-change colour when heated or cooled

Phosphorescent pigments-glow in the dark
Absorb natural or artificial light and store the energy in their molecules, released over a period of time as light


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Polymers-formed when lots of small molecules called monomers join together
Plastics are polymers and they are usually carbon based

Monomers that make up addition polymers have a double covalent bond

At least one double covalent bond between carbon atoms=unsaturated molecules (alkenes)
No double covalent bond=saturated compounds (alkanes)

Weak forces:
Plastic can be stretched easily, low melting point

Strong forces:
High melting points, can't be stretched 

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Complete combustion:
hydrocarbon + oxygen --> carbon dioxide + water
CH4 + 2O2 --> 2H2O + CO2

Happens when there is plenty of oxygen, gas burns with clean blue flame
Only produces two harmless waste products

Incomplete combustion:
hydrocarbon + oxygen --> carbon dioxide + water + carbon monoxide + carbon
4CH4 + 6O2 --> C + 2CO + CO2 + 8H2O

Happens when there isn't enough oxygen, smoky yellow flame
Carbon monoxide is poisonous and dangerous 

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Carbon Cycle


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