Chemistry

• Elements


  The primary constituents of matter, which cannot be chemically broken down into simpler substances
• Compounds


  Consist of atoms of different elements combined together
• By the end of this chapter, you should understand that elements are the primary constituents of matter, which cannot be chemically broken down into simpler substances, and compounds consist of atoms of different elements combined together
• Elements are the primary constituents of matter, which cannot be chemically broken down into simpler substances
• Compounds consist of atoms of different elements chemically bonded together in a fixed ratio
• Mixtures contain more than one element or compound in no fixed ratio, which are not chemically bonded and so can be separated by physical methods
• Kinetic molecular theory


  A model to explain physical properties of matter (solids, liquids and gases) and changes of state
• Temperature (K)


  A measure of average kinetic energy (Ek) of particles
• Distinguishing between properties of elements, compounds and mixtures

  1. Identify the different states of matter

  2. Use state symbols (s, l, g and aq) in chemical equations

  3. Interpret observable changes in physical properties and temperature during changes of state

  4. Convert between values in the Celsius and Kelvin scales
• Elements are the simplest substances and cannot be broken down or decomposed into simpler, more stable substances by a chemical reaction
• Elements


  Contain just one type of atom (which all have the same number of protons)
• Elements


  • Uranium, U
  • Cobalt, Co
• Elements are classified as metals, non-metals or metalloids
• The periodic table arranges all the elements in horizontal rows (periods, numbered 1 to 7) and vertical columns (groups, numbered 1 to 18)
• Elements can exist as atoms or molecules
• Molecule


  Two or more different atoms bonded (covalently)
• Each element is represented by a chemical symbol, consisting of either one or two letters
• The first letter of a symbol is always a capital (upper-case) letter and the second letter is always small (lower-case)
• The chemical and physical properties of a compound are always different from those of the elements that make it up
• Formation of a compound


  1. Heating iron with sulfur

  2. Chemical equation: Fe(s) + S(l) → FeS(s)
• Chemical reaction


  Formation of new chemical substances
• Dissolving


  A physical process where no new substances are formed
• Physical change


  Reversible change in physical properties
• Energy appears in different but related forms: kinetic, gravitational potential, elastic potential, internal, chemical, electrical, electromagnetic
• Law of conservation of energy


  Energy cannot be created or destroyed, only transferred from one form to another
• Solvation


  The interactions between solute particles and solvent molecules in a solution
• Hydration


  A specific type of solvation with water as the solvent
• Ion-dipole forces


  Electrostatic attraction between ions and the charged ends of water molecules
• Ionic substances are more soluble in water than other solvents due to ion-dipole forces
• Solvation shell/hydration sphere


  The solvent molecules around an ion
• Charge density


  The amount of charge located in a given volume
• Polar molecules


  Interact strongly with polar solvents through dipole-dipole interactions and/or hydrogen bonds
• Polar molecules tend to dissolve in polar solvents
• Miscible


  Two liquids that mix to form a homogeneous mixture
• Immiscible


  Two liquids that do not mix
• Charge density


  The large charge is located over a small volume
• Polar molecules


  Tend to dissolve in polar solvents
• Polar solvents


  • Methanol
  • Ethanol
  • Water
• Polar solvents contain -O-H groups that can form hydrogen bonds with ionic substances and polar molecules
• Miscible liquids


  Mix to form a homogeneous mixture: a single liquid of uniform composition