Natural science

• Atom


  Tiny particle that all matter is made up of
• Sub-atomic particles


  • Protons (positive charge)
  • Neutrons (no charge)
  • Electrons (negative charge)
• Nucleons


  Collective name for particles found in the nucleus, i.e. protons and neutrons
• An atom as a whole is usually uncharged (i.e. neutral) because it has an equal number of protons and electrons
• Proton


  • Found in nucleus
  • Positively charged
  • Number of protons identifies the atom
• Neutron


  • Found in nucleus
  • Uncharged
  • Exerts a binding force keeping protons together in the nucleus
• Electron


  • Moving around the nucleus
  • Negatively charged
  • It is the only particle that can leave an atom
• Nucleus


  • Central core of the atom
  • Contains all the protons and neutrons
  • Positively charged because of its protons
• Element


  • Composed of identical atoms
  • The simplest form of matter that cannot be broken down into simpler substances
• The number of protons determines the element, e.g. if an element has 6 protons, it can only be carbon
• Molecule


  • A combination of two or more atoms
  • Atoms of elements don't usually exist as single atoms, they tend to combine with other atoms
• Chemical bond


  • A force that binds two atoms together
  • This force is not easily broken
• Chemical formula


  • A way of representing the elements and the number of each element in one molecule of substance
  • Symbols of the elements and small numbers (subscripts) are used
• Diatomic molecule


  Composed of 2 atoms
• Triatomic molecule


  Composed of 3 atoms
• Polyatomic molecule


  Composed of >3 atoms
• Types of Chemical Reactions


  • Synthesis Reaction
  • Decomposition Reaction
• Synthesis Reaction


  A type of reaction in which two or more reactants combine to form a single product
• Synthesis Reaction


  1. Reactants combine

  2. Single product formed
• Decomposition Reaction


  A reaction where a single reactant produces many products
• Decomposition Reaction


  1. Single reactant

  2. Multiple products
• Synthesis Reaction


  • magnesium + oxygen → magnesium oxide
  • sodium + chlorine → sodium chloride
• Decomposition Reaction


  • water → hydrogen + oxygen
  • mercury oxide → mercury + oxygen
• Mixture


  At least two substances present (either elements, compounds or a combination)
• Mixtures


  • iron filings and sulfur
  • oxygen and nitrogen
  • iron filings and sugar
  • oxygen and carbon dioxide
  • water and alcohol
  • sugar and salt
  • air (oxygen, nitrogen, carbon dioxide)
• Mixtures


  • Individual components retain their properties and do not possess new properties
  • Constituents can be easily separated by simple physical methods
  • Substances can be mixed in any proportion
• Compounds


  • Contains at least two elements joined together chemically
  • Compound has new properties different from the individual elements
  • Elements in a compound cannot be separated without a chemical change
  • Elements in a compound are always present in a fixed proportion
• Diffusion in solids


  Solid particles are packed closely together and have little space to move around in, so they diffuse very slowly. Diffusion in solids is often referred to as "solid state diffusion" or "lattice diffusion."
• Diffusion in liquids


  Liquid particles move more slowly than gas particles, but they still diffuse relatively quickly because they have some space to move around in.
• Diffusion in gases

  Gas particles move quickly and have a lot of space to move around in, so they diffuse rapidly.
• Diffusion


  The process of particles spreading out from an area of high concentration to an area of low concentration.
• what is the definition of an atom


  tiny particles that are made up of matter