Conservation of Mass and Chemical Equations - Year 8 / KS3 Chemistry pptx, 431.9 KB. Lesson 1 - Chemical equations containing introduction to balancing equations and naming formulae. Lesson 2 - Conversation of Mass containing animations/illustrations using see-saw example. You can merge the lessons together if you have a double lesson or lesson longer than 50 minutes. Suitable for Year 8 / KS3 Chemistry.