Biology

• Biology Topics

  • Classification
  • Biodiversity
  • DNA Structure
  • Cell division Asexual sexual reproducti
  • Stem cells
  • Inheritance
  • Genes
  • Variation Evolution
  • The nervous system
  • Investigating reaction time
  • Homeo Stasis + Body temperature
  • Homeo Stasis + Blood Glucose
  • Microbes + diseases
  • The Natural Immune system
  • Preventing Diseases
  • Treating diseases
  • Developing new drugs
• Classification


  The process of organizing living things into groups based on their shared characteristics. Consists of 8 categories: domain, kingdom, phylum, class, order, family, genus, species.
• Biodiversity


  Refers to the variety of living organisms on Earth, including the number of different species, the genetic diversity within those species, and the variety of ecosystems in which they live.
• DNA


  A long molecule that contains the genetic instructions used in the development and function of all known living organisms. Made up of two strands that twist around each other to form a double helix, with each strand made up of four nucleotide bases: adenine (A), guanine (G), cytosine (C), and thymine (T). A always pairs with T, and G always pairs with C.
• Asexual Reproduction


  A type of cell division in which a single parent cell divides to produce offspring that are genetically identical to the parent.
• Acidic solution

  A solution with pH less than 7
• Alkaline solution

  • A solution with pH more than 7
  • An alkali is a base dissolved in water
• Neutral solution

  pH 7
• Acids

  Contain hydrogen ions, H+
• Alkalis

  Contain hydroxide ions, OH-
• Strong acid

  An acid which completely dissociates to release H+ ions in an aqueous solution
• Weak acid

  An acid which partially dissociates to release H+ ions in an aqueous solution
• Strong base

  A base which completely dissociates to release OH- ions in an aqueous solution
• Weak base

  A base which partially dissociates to release OH- ions in an aqueous solution
• Product formed when a metal is added to dilute acid

  Acid + Metal -> Salt + Hydrogen
• Neutralisation reactions of dilute acids

  • Acid + Alkali -> Salt + Water
  • Acid + Base -> Salt + Water
  • Acid + Metal carbonate -> Salt + Water + Carbon dioxide
• Neutralisation

  The reaction of hydrogen ions, H+, with hydroxide ions, OH-, to form water, H2O
• Test for presence of carbonates

  1. Carbonates react with dilute acids to form carbon acid

  2. Gas formed can be bubbled through limewater, if limewater turns cloudy the gas is CO2
• Preparing crystals of soluble salts

  1. Measure a set volume of acid

  2. Heat the acid gently

  3. Add the chosen base in excess, the acid has been neutralised when excess solid sinks to the bottom

  4. Filter the excess base using filter paper and a funnel

  5. Heat the salt solution to evaporate the water

  6. Leave the rest to evaporate slowly so crystals of the salt form
• Soluble salts

  Can be made from acids by reacting them with insoluble substances, such as metals, metal oxides, hydroxides or carbonates
• Salts formed from hydrochloric acid, nitric acid and sulfuric acid

  • Hydrochloric acid produces chlorides
  • Nitric acid produces nitrates
  • Sulfuric acid produces sulfates
• Test for sulfate ions

  1. First add dilute hydrochloric acid, followed by barium chloride solution

  2. A white precipitate will form if sulfate ions are present in the solution
• Titration

  • A method to prepare solutions of soluble salts
  • To determine the relative and actual concentrations of solutions of acids/alkalis
• Concentration of a solution

  • Concentration = mol ÷ volume
  • The units of concentration are mol dm-3
• Concentration of an acid/base

  The amount of substance present - the number of moles of that acid/base in solution
• Strength of an acid/base

  To the degree of ionisation of the acid or base - how readily the acid releases H+ ions or how readily the base releases OH- ions
• Preparing insoluble salts

  1. Insoluble salts can be formed in a precipitation reaction

  2. React 2 solutions which contain the ions of the desired salt

  3. A solid precipitate of your salt is produced

  4. Filter the salt out using a filter paper and funnel

  5. Wash the salt with distilled water and leave it to dry on the filter paper