Chemistry

• Elements and atoms

  The key molecules that are required to build structures that enable organisms to function
• Key molecules

  • Carbohydrates
  • Proteins
  • Lipids
  • Nucleic Acids
  • Water
• Monomers

  Smaller units from which larger molecules are made
• Polymers


  Molecules made from a large number of monomers joined together in a chain
• Synthetic polymers

  • nylon
  • polyethylene
  • polyester
  • Teflon
  • epoxy
• Enzyme catalysis

  1. Substrate binding

  2. Transition state facilitation

  3. Catalysis

  4. Release
• Enzymes

  • They increase the rate of chemical reactions without themselves being consumed or permanently altered by the reaction
  • They increase reaction rates without altering the chemical equilibrium between reactants and products
• As temperature increases

  The rate of reaction increases
• Every substance in our world is made up from chemical elements
• Chemical elements cannot be broken down further into simpler substances by chemical means
• A few elements, such as nitrogen and gold, are found on their own in nature, not combined with other elements
• Most elements are found in combination with other elements as compounds
• Chemical symbol

  The symbols are often derived from Latin or Greek words
• Atom


  The smallest part of an element that can take part in a chemical change
• Atoms are very small, the diameter of a hydrogen atom is approximately 10^-10 m
• A single hydrogen atom weighs only 1.67 × 10^-27 kg
• Atom structure

  • Nearly all of its mass is concentrated in a tiny region in the centre called the nucleus
  • The nucleus is made up of protons and neutrons
  • Outside the nucleus, electrons move around in regions of space called orbitals
• Nucleons

  Particles in the nucleus, including protons and neutrons
• Electron shells

  Regions of space around the nucleus where electrons move, each at a particular energy level
• In a neutral atom, the number of electrons is equal to the number of protons
• Most of the atom is empty space, if the diameter of an atom were the size of a football stadium, the nucleus would only be the size of a pea
• Electrons are even smaller than protons and neutrons
• Experiments with subatomic particles

  1. Fire a beam of electrons past electrically charged plates

  2. Electrons are deflected away from negative plate and towards positive plate

  3. Cathode-ray tube used to produce beams of electrons

  4. Electrons given off from heated wire and attracted to positively charged metal plates
• Electrons

  • Have a negative charge
  • Have a very small mass
• Protons

  • Have a positive charge
  • Much heavier than electrons
• Neutrons

  • Uncharged
• Like charges repel each other and unlike charges attract each other
• Protons are about 2000 times heavier than electrons
• Relative mass and charge

  Electrons: mass -1, charge -1<|>Neutrons: mass 1, charge 0<|>Protons: mass 1, charge +1
• Beam of electrons passing close to highly negatively charged plate

  Electrons deflected away from plate
• Atomic (proton) number

  The number of protons in the nucleus of an atom
• Every atom of the same element has the same number of protons in its nucleus
• The atomic number makes an atom what it is, e.g. an atom with 11 protons is sodium
• Subatomic particle

  Symbol<|>Relative mass<|>Relative charge
• A beam of electrons is passing close to a highly negatively charged plate. When the electrons pass close to the plate, they are deflected away from the plate.
• The number of protons in the nucleus of an atom is called the atomic number (proton number) (Z). Every atom of the same element has the same number of protons in its nucleus.
• The mass number (nucleon number) (A) is the number of protons plus neutrons in the nucleus of an atom.
• How to find the number of neutrons

  1. mass number = number of protons + number of neutrons

  2. number of neutrons = mass number - atomic number
• Atoms of the same element that have different numbers of neutrons are called isotopes.
• Isotopes are atoms of the same element with different mass numbers.