Unit 7.4 Classifying life Unit 7.5 Explaining properties of matter Unit 7.6 Energy and sound [BIOLOGY] Characteristics of living organisms What is a species - reproduce, fertile, offspring Dichotomous keys Classification, viruses, living and non-living [CHEMISTRY] Physical and chemical properties Acids, alkalinity, pH Indicators, Universal indicators, litmus Neutralisation Alloys as mixtures Particle model - hardness, pure metals and alloys [PHYSICS] Types of energy Energy transfers - Sankey Keys Sound Waves, vacuum Echoes - Reflection of sound