Chemistry

• Reversible reaction


  A reaction with a double arrow in the middle, indicating it can react in both forward and backward directions
• Reversible reaction


  1. Forward reaction

  2. Backward reaction
• Equilibrium


  The point where the forward and backward reactions are occurring at the same rate, so there is no overall change in concentrations
• Position of equilibrium


  The relative concentrations of reactants and products at equilibrium, which can shift left or right depending on conditions
• Adding heat to the reaction

  Encourages the forward reaction, shifting the position of equilibrium to the right
• Cooling the reaction

  Pushes the position of equilibrium back to the left
• Reversible reactions can only reach equilibrium in a closed system</b>
• Exothermic


  A reaction that releases heat energy
• Endothermic


  A reaction that absorbs heat energy
• Reversible reactions are always exothermic in one direction and endothermic in the other
• Hydrated


  Containing water
• Anhydrous


  Containing no water
• Thermal decomposition of hydrated copper sulfate

  1. Heating drives the forward endothermic reaction, producing anhydrous copper sulfate

  2. Adding water drives the backward exothermic reaction, reforming the hydrated copper sulfate
• Atom

  Basic structure is a central nucleus surrounded by electrons which orbit around the nucleus in rings that we call shells
• Particles that make up the nucleus

  • Protons
  • Neutrons
• Electrons


  • Have a mass 2000 times smaller than protons and neutrons
  • Have a negative charge of 1-
• Atoms have a radius of around 0.1 nanometers
• Most of an atom is actually empty space
• Electrons are even smaller than the nucleus and would be too small to see in the atom diagram
• Ion

  An atom that has lost or gained electrons, so the positive and negative charges no longer balance
• Atomic number

  Tells us how many protons the atoms of that element have
• Mass number


  Tells us the total number of neutrons and protons in that atom
• The number of protons and electrons in an atom is always the same
• Exothermic reaction


  A reaction that releases heat into the surroundings
• Equilibrium


  A state in which the rate of the forward reaction is equal to the rate of the reverse reaction
• Le Chatelier's principle


  A principle that states that if a system at equilibrium is disturbed, the system will respond in a way that counteracts the disturbance
• Closed system


  A system in which no matter or energy can enter or leave
• "Reversible reactions can only reach equilibrium in a closed system"


  In a reversible reaction, the concentrations of reactants and products will only become constant (i.e., reach equilibrium) if the system is closed, meaning no matter or energy can enter or leave.
• pH scale


  Measure of how acidic or alkaline a solution is, ranging from 0 to 14 with low numbers being most acidic and high numbers being most alkaline
• Neutral substances like pure water have a pH of 7, which is neither acidic nor alkaline
• Acidic substances


  • Stomach acid (pH 2)
  • Acid rain (pH 4)
• Alkaline substances


  • Washing up liquid (pH 9)
  • Bleach (pH 12)
• Measuring pH


  1. Using an indicator (chemical dyes that change color)

  2. Using a pH probe connected to a pH meter
• Indicator


  A group of chemical dyes that change color depending on the pH, some are wide range indicators like universal indicator
• pH probe and meter


  Can provide more accurate and precise pH measurements than indicators
• Acid


  Any substance that forms aqueous solutions with a pH less than 7, releasing hydrogen ions in water
• Alkali


  A subgroup of bases that are soluble in water, forming hydroxide ions
• Neutralization reaction


  Reaction between an acid and a base, producing a salt and water
• Differences between chemical and physical changes


  • Physical changes: No new substances are formed
  • Chemical changes: New chemical substances are formed
• Differences between chemical and physical changes


  • Physical changes: Can easily be reversed
  • Chemical changes: Difficult to reverse