combined science aqa paper 1 chemistry

• This is a revision video for a GCSE combined science chemistry paper 1
• It covers all the key information but not in a huge amount of detail because otherwise it would be about 40 hours long
• The idea is that you can use this video to give you an overview of everything on the paper and also that you can use it as a last minute cram right before the exam
• Elements


  The smallest part of an element that can exist and still be that element
• There are about a hundred different elements and they are shown in the periodic table
• Compounds


  Formed when elements combine together in chemical reactions, containing two or more elements chemically combined in fixed proportions
• Fixed proportions


  The same ratio of elements
• Naming compounds from their formula

  1. Take the name of the metal and leave it as it is

  2. Take the first syllable of the name of the nonmetal

  3. Add 'ide' on the end
• Naming compounds with three elements including oxygen


  1. Start the same as before

  2. Add the first syllable of the nonmetal

  3. Add 'ate' on the end
• Mixture


  Two or more elements or compounds that are not chemically combined together, not bonded
• Physical separation processes


  • Filtration
  • Crystallization
  • Simple distillation
  • Fractional distillation
  • Chromatography
• Filtration


  • Used to separate an insoluble solid from a liquid
  • The insoluble solid stays on the filter paper (residue)
  • The liquid goes through the filter paper (filtrate)
• Crystallization


  • Used to separate a soluble solid from a liquid
  • The liquid evaporates leaving the solid behind
• Fractional distillation


  • Separates a mixture of liquids based on their different boiling points
  • The mixture is heated at the bottom and a temperature gradient develops in the column
  • Liquids condense at different points and can be collected separately
• Chromatography


  • Separates a mixture of liquids or dyes based on their solubility
  • The sample is placed on a stationary phase (e.g. paper)
  • A mobile phase (solvent) moves up the stationary phase, carrying the components at different rates
• Atom


  The smallest part of an element that can exist and still be that element
• Parts of an atom

  • Protons (positive particles in the nucleus)
  • Neutrons (neutral particles in the nucleus)
  • Electrons (negative particles orbiting the nucleus)
• The average size of an atom is about 0.1 nanometres
• The nucleus is only one ten-thousandth of the diameter of the atom
• The relative mass of the electron is not zero, it is very small (about 1/1840 of the mass of a proton)
• Isotopes


  Atoms of the same element with different numbers of neutrons
• Calculating the number of protons, electrons and neutrons in an atom


  Use the information given about the atomic number and mass number
• Dalton model

  Atoms are indivisible, hard spheres
• Thomson (plum pudding) model

  Atoms have a positive charge with electrons embedded in it
• Rutherford model


  Atoms have a tiny, dense, positive nucleus surrounded by empty space with electrons orbiting
• Bohr model


  Electrons orbit the nucleus in distinct shells at different energy levels
• Periodic table


  Arranges elements in order of atomic number, with elements with similar properties in vertical groups
• The periodic table was originally arranged by atomic weight, which had some issues
• The periodic table is now arranged by atomic number, which fixes the issues with the original arrangement
• Elements in the same group have the same number of electrons in their outer shell, which determines their chemical properties
• Electrons in outer shell


  Determines how an element reacts with other elements
• The periodic table hasn't always been laid out like this
• Initially, elements were arranged according to their atomic weight, which led to some problems
• Dmitri Mendeleev left gaps in the periodic table and made predictions about undiscovered elements, which turned out to be correct
• Metals


  Elements that will react to form positive ions
• Nonmetals


  Elements that will react but won't form positive ions
• Metals


  • Malleable
  • Conductive
  • High melting points
• Group 1 (Alkali metals)


  • Lithium
  • Sodium
  • Potassium
• Alkali metals


  • Very reactive
  • Less dense than water
  • Produce hydrogen gas when reacting with water
  • Produce a lilac flame when potassium burns
  • Produce a metal hydroxide (alkali) when reacting with water
• Group 7 (Halogens)


  • Fluorine
  • Chlorine
  • Bromine
  • Iodine