Paper 1 - C1-C7

• In an element, all of the atoms are the same.
• Compounds contain two or more different elements chemically combined in fixed proportions.
• Compounds usually have different properties to the elements that they're made from.
• A molecule has any elements chemically combined even if they are the same element.
• The Periodic Table shows all the elements.
• Physical separation techniques can only be used to separate mixtures.
• Filtration is used to separate an insoluble solid from a liquid.
• Insoluble


  The solid will not dissolve in the liquid.
• The liquid passes through the tiny pores in the filter paper.

  A) filtrate

  B) residue

  C) filter paper

  D) filter funnel

  E) clonical flask

  
• Crystallisation is used to separate a soluble solid from a liquid.
• Aqueous solution


  When a soluble solid dissolves into a liquid.
• You can leave the solution out and the liquid will slowly evaporate, otherwise:

  A) gauze

  B) tripod

  C) solution

  D) bunsen burner

  E) evaporating basin

  
• Simple distillation is used if you want to keep the liquid.

  A) water out

  B) water in

  C) condenser

  D) pure liquid

  E) solution

  F) thermometer

  G) heat

  H) flask

  I) beaker

  
• Fractional distillation is used to separate a mixture of different mixtures of liquids (miscible liquids).

  A) fractionating

  B) column

  C) glass

  D) thermometer

  E) water out

  F) water in

  G) condenser

  H) mixture

  I) miscible liquids

  J) pure liquid

  K) heat

  L) beaker

  M) flask

  
• Fractional distillation


  Both liquids will start to evaporate but the one with the lower boiling point will evaporate more easily. So we now have a mixture of two different vapours making their way into the fractionating column. When the vapours reach the fractionating column they condense and drip back into the flask where the liquids evaporate again. The repeated evaporating and condensation increases the amount of the lower boiling point chemical in the fractionating column.
• Paper chromatography allows us to separate substances based on their different solubilities.

  A) chromatography paper

  B) direction

  C) motion

  D) solvent

  E) solvent

  F) pencil line

  
• Paper Chromatography


  We call the paper the stationary phase because the paper does not move. We call the solvent the mobile phase because the solvent moves. If there's one spot, the colour is a single pure colour. If there's more than one spot, the colour was a mixture of different colours. A more soluble substance is more attracted to the mobile phase than a less soluble solvent. So a more soluble substance travels further.
• The idea of atoms has been around for a long time.
• Thousands of years ago, the Ancient Greeks believed that everything is made of atoms. They believed that atoms are tiny spheres which cannot be divided. That idea was accepted for hundreds of years.
• In 1897, scientists discovered that atoms contain tiny negative particles which the scientists called electrons.
• The discovery of electrons told scientists that atoms are not tiny spheres that cannot be divided. Instead, atoms must have an internal structure.
• Scientists now suggested a new model for the structure of atoms. They called it the plum pudding model.

  A) positive charge

  B) electron

  
• Plum Pudding Model


  A ball of positive charge with negative electrons embedded in it.
• Scientists wanted to know if the Plum Pudding model was correct. To find out, they carried out an experiment called the alpha scattering experiment.
• Alpha Scattering Experiment


  The scientists used gold foil as they were able to hammer gold into very thin foil just a few atoms thick. Scientists then fired tiny positively charged alpha particles at the gold foil. The scientists found that most of the alpha particles passed straight through the gold foil without changing direction. Sometimes, an alpha particle was deflected as it passed through the gold foil and an alpha particle simply bounced straight back off the gold foil. Because the alpha particles went straight through the gold foil, scientists knew that atoms are mainly empty space.
• Because some of the alpha particles were deflected this told the scientists that the centre of the atom must have a positive charge.
• Because some alpha particles bounced straight back this told the scientists that the centre of an atom must conatin a great deal of mass. We now call the central part of an atom the nucleus.
• Scientists replaced the plum pudding model with the nuclear model.
• Nuclear Model:

  A) empty space

  B) electrons

  C) positively charged nucleus

  
• The Nuclear Model


  Most of the atom is simply empty space. In the centre of the atom, we have a tiny positive nucleus containing most of the mass of the atom. Around the edge of the atom, we have negative electrons.
• Bohr Model:

  
• The scientist Neils Bohr proposed that electrons orbit the nucleus at specific distances rather than just in a general area. This idea was based on calculations that Bohr had carried out. We now call the orbits energy levels or shells.
• Several years after the Bohr Model, scientists found that the positive charge in the nucleus is due to tiny positive particles which are called protons.
• The number of protons determines the amount of positive charge in the nucleus.
• Around 20 years after the nuclear model was first proposed, the scientist James Chadwick made a final important discovery. Chadwick discovered that the nucleus also contains neutral particles which he called neutrons.
• The radius of an atom = 0.1 nanometres / 1x10^-10m
• The radis of the nucleus = 1x10^-14m
• Relative Charge:

  Proton: +1

  Neutron: 0

  Electron: -1
• Relative mass:

  Proton: 1

  Neutron: 1

  Electron: Very small
• Relative charge


  The charge of one particle compared to another particle.