science chemistry

• What are the main hazard symbols mentioned in the study material?

  Corrosive, Toxic, Explosive, Flammable, Caution
• What does the corrosive hazard symbol indicate?


  It indicates that a substance can burn the skin.
• What does the toxic hazard symbol signify?


  It signifies that a substance can cause harm by poisoning.
• What does the explosive hazard symbol mean?


  It means that the substance can explode.
• What does the flammable hazard symbol indicate?


  It indicates that a substance can catch fire easily.
• Why are hazard symbols used instead of words?


  They have greater visual impact than words and can be understood irrespective of language.
• What pH value is considered neutral?


  pH 7
• How are acids and bases classified based on pH?


  Acids have a pH lower than 7, and bases have a pH higher than 7.
• What is an alkali?


  An alkali is a base that dissolves in water.
• What are the examples of strong and weak acids and alkalis provided in the study material?

  • Strong acids: Hydrochloric acid, Sulfuric acid
  • Weak acid: Ethanoic acid
  • Strong alkalis: Sodium hydroxide, Potassium hydroxide
  • Weak alkali: Ammonia
• What are some common household acids and bases mentioned in the study material?

  • Vinegar: Contains ethanoic acid
  • Lemon juice: Contains citric acid
  • Baking soda: Contains sodium hydrogencarbonate
  • Milk of Magnesia: Contains magnesium hydroxide
  • Cleaning products: Often contain ammonia
  • Oven and drain cleaners: Often contain sodium hydroxide
• What is the purpose of indicators in chemistry?


  Indicators tell us whether a substance is neutral, acid, or alkaline.
• What are natural indicators mentioned in the study material?


  Beetroot, blackcurrant, and red cabbage.
• How can natural indicators be made?


  By chopping the plant, adding water, grinding the mixture, and filtering it.
• What is the difference between a natural indicator and a universal indicator?


  A universal indicator can tell the strength of an alkali or acid, while natural indicators cannot.
• What are the colors of universal indicator at different pH values?


  • pH 0: Red (Strong acid)
  • pH 1: Orange (Strong acid)
  • pH 2: Yellow (Weak acid)
  • pH 3: Green (Weak acid)
  • pH 4: Green/Blue (Neutral)
  • pH 5: Blue (Weak alkali)
  • pH 6: Blue (Strong alkali)
• What happens when an alkali is added to an acid?


  The pH changes from a low value to a higher pH value, described as neutralisation.
• What is used to test for carbon dioxide gas?


  Limewater.
• What happens to limewater when carbon dioxide is bubbled through it?


  Limewater turns from colourless to cloudy.
• How can hydrogen gas be tested?


  By inserting a burning splint into the test tube containing hydrogen.
• What indicates the presence of oxygen gas?


  A glowing splint will relight when placed in a test tube containing oxygen.
• What are the three states of matter?

  • Solids
  • Liquids
  • Gases
• How are particles arranged in solids?


  Particles are held close together in a regular pattern by strong forces.
• How are particles arranged in liquids?


  Particles are close together and move over each other as forces are weaker.
• How are particles arranged in gases?


  Particles can be large distances apart and move randomly.
• What is the term for a liquid changing into a solid?

  Freezing.
• What is an element?


  A pure chemical substance made from only one type of atom.
• What is a compound?


  A substance that has two or more elements chemically joined together.
• What is a mixture?


  A mixture contains two or more different substances that can be separated.
• What are the examples of elements, compounds, and mixtures provided in the study material?


  • Element: Hydrogen (H₂)
  • Compound: Calcium carbonate (CaCO₃)
  • Mixture: Saltwater
• What do state symbols in balanced symbol equations indicate?


  They show the state of each substance: solid (s), liquid (l), gas (g), and aqueous solution (aq).
• What are the methods of separation mentioned in the study material?

  • Filtration
  • Crystallisation
  • Simple distillation
  • Paper chromatography
• What is the purpose of filtration?

  Filtration separates an insoluble solid from a liquid.
• What is the process of evaporation used for?


  To separate a dissolved solid from the liquid it is dissolved in.
• How does crystallisation work?


  It separates a dissolved solid from its solvent by cooling the solution.
• What is simple distillation used for?


  To separate the solvent from a solution, such as pure water from seawater.
• What is the process of distillation?


  • Involves both evaporation and condensation
  • Used to separate a solvent from a solution
• What is the term for a solid that dissolves in a liquid?

  Soluble.
• What is the term for a solid that does not dissolve in a liquid?


  Insoluble.
• What is the term for the liquid that dissolves a solid?

  Solvent.