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Formulae and Equations (Conversions 1.2 (Evaporation and boiling…
Formulae and Equations
States of matter 1.1
Solid - particles are closely packed with fixed positions in a regular arrangement. Particles can vibrate but not move. Most amount of kinetic energy.
Liquid - particles are mainly touching but some gaps and they are less regularly arranged. Particles can move slowly.
Gas
- particles are widely spaced with no forces between particles. Particles are free to move with rapid and random movement. Least amount of kinetic energy.
Conversions 1.2
Melting and boiling lose kinetic energy and become less regularly arranged.
Freezing and condensing gain kinetic energy and become more regularly arranged.
Melting = freezing point, boiling = condensing point IF PURE
Sublimation requires heating because energy is required to break forces of attraction between particles. Gain kinetic energy and become less regularly arranged.
Evaporation and boiling differences
Evaporation can occur at any temperature between the melting and boiling point. Only the particles at the surface of the liquid evaporate and there are no bubbles unlike boiling. Evaporation - gradual, boiling - sudden.
Arrangement 1.8/1.14
Element - consists of one type of atom and cannot be broken down into similar substances by chemical means (heat or electricity)
Compound - contains 2 or more types of elements chemically joined in fixed proportions. They have different properties from the elements which they were made.
Mixture - contains 2 or more chemical substances not chemically joined and not in fixed proportions.
Molecule - fixed number of atoms chemically joined together (by covalent bonds)
Atom - the smallest unit of the element that behaves as the element.
pure and mixtures 1.9
Pure substances melt and boil over a range of temperatures.
Mixtures melt and boil over a range of temperatures
Melting point is used to decide whether a solid is pure or not. Pure solids will have a sharp m.pt. which agrees with the literature value.
Word equations and balancing 1.25
Atoms are rearranged to make new substances
Reactants are on the left and products are on the right and are new substances produced from a reaction
The total mass of the reactants is the same as the total mass of products.
Only use large numbers to balance but never change the small numbers.
State symbols e.g. s, l, g, aq, represent solids, liquids, gases and aqueous vapour. Aqueous means dissolved in water and water is only a common liquid.
examples of sublimation
Dry ice - carbon dioxide appears as solid dry ice as gas bubbles rise from the beaker.
Iodine - gas hits cold surface and makes crystals - colour change from grey to purple.
Energy breaks attraction between particles and they now have a less regular pattern so are a gas.
1.26
Relative formula mass
Add relative atomic masses (top number on periodic table) of all chemical substances.
Relative formula mass can also be called relative molecular mass and mass of 1 mole.
1.39 formulae
metals in groups 1, 2 and 3 and non'metals in 5, 6, 7. Metals - positive, non-metals - negative. Metals in group 1,2,3 have positive valency equal to group number. Non-metals in group 5,6,7 have negative valencies to 8- group number.
acids - hydrochloric (HCl), sulphuric (H
2
SO
4
), nitric (HNO
3
). Molecules - water (H
2
O), ammonia (NH
3
), carbon dioxide (CO
2
).
Ag (1), Cu (2), Fe (2), Fe (3), Pb (2), Zn (2)
H(1), hydroxide(OH(1)), ammonium(NH
4
), carbonate(CO
3
- 2), nitrate(NO
3
(1)), sulfate(SO
4
(2))