Chemistry C1

• • a mixture is made up of two or more substances that are not chemically combined together
  • mixtures can be separated by physical means, such as filtration, crystallisation, and simple distillation.
• No new atoms are ever created or destroyed in a chemical reaction: the total mass of reactants = the total mass of products
• There is the same number of each type of atom on each side of a balanced symbol equation
• State symbols in balanced symbol equations

  • (s) for solids
  • (l) for liquids
  • (g) for gases
  • (aq) for aqueous solutions
• Atom


  The smallest part of an element that can exist
• All substances are made of atoms
• There are about 100 different elements
• Element


  Substances shown in the periodic table
• Compound

  Formed from elements by chemical reactions, contains two or more elements chemically combined in fixed proportions, can be represented by formulae using the symbols of the atoms from which they were formed, can only be separated into elements by chemical reactions
• The periodic table lists all the chemical elements, with eight main groups each containing elements with similar chemical properties
• Elements contain only one type of atom
• Compounds contain more than one type of atom
• Atom


  Has a tiny nucleus at its centre, surrounded by electrons
• Solvent


  The substance that we dissolve the colours in (water in this experiment)
• Solute


  The substances that are dissolved in the solvent
• Chromatogram


  The piece of chromatography paper showing how the dyes have separated
• Paper chromatography


  1. Separates mixtures of substances dissolved in a solvent as they move up a piece of chromatography paper

  2. Different substances are separated because of their different solubilities in the solvent used
• Plum pudding model


  • Has a ball of positive charge
  • Has electrons embedded in the positive charge at random positions
• Nuclear model


  • Has protons (positive charge) in the nucleus
  • Has electrons in shells orbiting the nucleus
  • Has a nucleus (positive dense, mass concentrated in the centre)
  • Has neutrons
• Nucleus


  • Made up of protons and neutrons
  • Positively charged because of the protons
  • Dense because it contains all the mass of the atom in a tiny space
• Electrons


  • Very small and light, and negatively charged
  • Able to be lost or gained in chemical reactions
  • Found thinly spread around the outside of the nucleus, orbiting in layers called shells (energy levels)
• Each element has a definite and fixed number of protons
• All the atoms of a particular element always contain the same number of protons
• If the number of protons changes, then the atom becomes a different element
• Electrons have a mass of almost zero, which means that the mass of each atom results almost entirely from the number of protons and neutrons in the nucleus
• In an atom, the number of electrons is equal to the number of protons in the nucleus
• Atoms have no overall electrical charge
• The number of protons in an atom of an element is its atomic number
• Atoms of different elements have different number of protons
• Atoms are made of protons, neutrons, and electrons
• Protons have a relative charge of +1, and electrons have a relative charge of –1
• Neutrons have no electric charge, they are neutral
• The relative masses of a proton and a neutron are both 1
• Atoms contain an equal number of protons and electrons, so carry no overall charge
• Atomic number = number of protons (= number of electrons)
• Mass number = number of protons + neutrons
• Atoms of the same element have the same number of protons (and hence electrons) in their atoms
• Ion


  Charged atom or particle
• Isotope


  An atom with the same number of protons but different numbers of neutrons
• Atom


  The smallest particle that can exist on its own