59 SUBJECT Physics TOPIC FROM CURRICULUM GENERAL TOPIC: SUBTOPIC DENSITY, PRESSURE AND LIFT Density and specific gravity LEARNING OBJECTIVES ● They know what homogeneous bodies are, ● separate homogeneous bodies from inhomogeneous ones, ● the difference between substances of different densities, ● by comparing densities or average densities, explain under which circumstances, the body floats, swim or sinks. Experimentally investigate buoyancy (E). ART EXPRESSIOSIONS/VISUAL FORMS USED Lava light SPECIAL REQUIREMENTS Substances and accessories: - edible oil, - water, - magnesium effervescent tablets, - food colouring, - glass flasks, - pumpkin stand. MOTIVATIONAL STAGE TITLE OF THE LESSON Oil and water ISSUE/PROBLEM (society issue, issue that is seen relevant from pupils’ perspective, issue linked to some nature phenomenon or phenomenon from pupils’ everyday life) Oil spill in an accident. Why does oil float on water? INVESTIGATIONAL STAGE DESCRIPTION OF THE ACTIVITY Demonstration of the difference in density of water and oil. Effervescent tablets contain magnesium carbonate, citric acid… The reaction between magnesium carbonate and water results in the formation of carbon dioxide, which rises in the form of bubbles towards the surface of the flask. Water and oil do not mix. The oil has a lower density and therefore floats on water. Carbon dioxide rises in bubbles towards the surface and carries the dye with it.