chem paper 1

• Substances are made of atoms represented in the periodic table by a symbol

  • A compound contains two or more different types of atoms chemically bonded together
  • Chemical formula example: H2O (hydrogen and oxygen atoms)
• Atoms change what they're bonded to and how they're bonded through chemical reactions

  • Word equation and chemical equation represent reactions
  • Atoms are not created or destroyed in any chemical reaction
• Balancing equations:

  • Start balancing atoms only in compounds
  • Example: Balancing H2O with 2 in front of it to balance hydrogen atoms
• Mixtures:

  • Combination of different types of elements and compounds not chemically bonded
  • Example: Air (oxygen, nitrogen, etc.)
  • Solutions like saltwater are mixtures
• Separation techniques:

  • Filtration for insoluble particles from a liquid
  • Crystallization leaves solid dissolved in liquid behind
  • Distillation separates liquids with different boiling points
• States of matter:

  • Solid, liquid, gas (e.g., ice, water, water vapor)
  • Melting and evaporating require energy to overcome forces of attraction
• Atomic structure:

  • Atoms have protons, neutrons, and electrons
  • Atomic number = number of protons, determines element
  • Atoms with different numbers of neutrons are isotopes
• Periodic table:

  • Atomic number at the bottom, mass number at the top
  • Atoms are neutral with equal protons and electrons
  • Ions form when atoms gain or lose electrons
• Electron configuration:

  • Electrons fill shells with max 2, 8, 8, 2 electrons
  • Transition metals have unique electron configurations
• Bonding:

  • Metal atoms bond through metallic bonding
  • Non-metals bond through covalent bonding to form molecules
  • Ionic bonding between metals and non-metals
• Ionic compounds:

  • Consist of positive and negative ions in a lattice
  • High melting points, conduct electricity in liquid form
• Covalent compounds:

  • Simple molecular structures with weak intermolecular forces
  • Giant covalent bonding forms one giant molecule (e.g., diamond, graphite)
• Carbon allotropes:

  • Diamond and graphite are examples
  • Graphene, fullerenes, and nanotubes are other allotropes
• Nanoparticles:

  • Structures between 100 and 2,500 nm in size
  • High surface-to-volume ratio compared to larger particles
• Conservation of mass:

  • Total mass of all substances conserved in a chemical reaction
• Total mass of all substances is conserved in a chemical reaction
• Atoms that go in must come out, so equations must be balanced
• Relative atomic mass is known, but for compounds, we can add these up to give the relative formula mass
• One mole of a substance has a mass equal to its relative atomic or formula mass
• Moles can be calculated using the formula: moles = mass / RAMs
• In a reaction, the ratio of moles of one substance to another is important (stoichiometry)
• Moles can be used to predict how much of a reactant is needed in a reaction
• Concentration of solutions can be given in g/dm^3 or moles/dm^3
• More reactive metals displace less reactive metals from compounds
• Atom economy tells us how much of a desired product is obtained compared to the mass of reactants
• Percentage yield tells us how much product is actually made compared to the theoretical maximum
• Metals vary in reactivity, and the reactivity series helps predict reactions
• One mole of any gas occupies a volume of 24 dm^3 at room temperature and pressure
• Reduction and oxidation happen in reactions depending on electron gain or loss
• Acids and bases react to form salts and water
• pH scale is logarithmic, with lower pH indicating higher acidity
• Strong acids completely dissociate, while weak acids only partially dissociate
• Titrations are used to determine the concentration of acids or alkalis
• Electrolysis involves the movement of ions in a solution or molten compound to produce new substances
• Energy changes in reactions can be exothermic (energy released) or endothermic (energy absorbed)
• Activation energy is the energy needed to start a reaction
• Batteries contain chemicals that produce a potential difference to power electrical appliances
• Rechargeable batteries can be recharged by causing the reverse reaction to occur
• Hydrogen fuel cells split water into hydrogen and oxygen to produce a voltage