C5: Chemical Changes

• What is an acid?


  A substance that when aqueous creates a Ph less than 7 and release H+ ions
• What is a base?

  A substance that has a Ph more than 7
• What is an alkaline?

  A base that when aqueous forms a solution with a Ph more than 7 and releases OH- ions
• What scale is pH measured on?


  0-14
• What pH does pure water have?

  pH 7 (neutral)
• What examples of pH are there

  Stomach acid (pH 2)Acid rain (pH 4)Water (pH 7)Toothpaste (pH 9)Bleach (pH11)
• Name 3 pH indicators

  1. Litmus paper 2. Universal indicator 3. pH probe
• What are the advantages and disadvantages of litmus paper?

  A: Shows you if a solution is acid or alkalineD: Doesn't tell you the pH
• What are the advantages and disadvantages of Universal indicator?

  A: More accurate reading as it displays a variety of colours over the whole pH scale D: Doesn't tell you the exact pH
• What are the advantages and disadvantages of the pH probe?

  A: Tells you the exact pH a solution is D: Expensive and needs regular cleaning
• What is a neutralisation reaction

  acid + alkali -> salt + water
• What is the formula for Hydrochloric acid


  HCl
• What is the formula for Nitric acid

  HNO3
• What is the formula for sulfuric acid


  H2SO4
• What is a strong acid

  An acid that is completely ionised in aqueous solution
• What is a weak acid?

  An acid that is only partially ionised in aqueous solution
• What are some examples or weak acids

  1. Ethanoic acid (CH3COOH) 2. Citric acid 3. Carbonic acid
• Give three examples of a strong acid

  Hydrochloric acid, Sulfuric acid, Nitric acid
• What is acid strength?

  How many acid molecules that ionise in water
• What is acid concentration


  how much acid there is in a certain volume of water
• What happens when the pH scale decreases by 1

  The H+ ions increase by x10
• What happens when a metal oxide/ hydroxide reacts with acid?

  Salt and water is produced
• What happens when metal carbonate reacts with acid

  Salt, water and carbon dioxide is produced
• How do you do crystallisation?

  1. Gently heat a dilute solution of acid in a water bath 2. Add insoluble base into your acid in excess 3. Filter out excess base 4. Heat your dissolved soluble salt gently with a bunsen burner to avoid damaging crystals 5. Leave to naturally evaporate