C1
- Created by: soph_hopkins
- Created on: 13-06-14 19:54
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
Emulsifiers
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
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
Perfumes
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
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
Solutions
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
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
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
Polymers
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
Combustion
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
Carbon Cycle
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