Layering Liquids

The Grade Two students are almost complete their "Exploring Liquids" unit in Science.  We are practising the scientific method/procedures as we do the experiments and trying to observe, hypothesize and talk like scientists.  This was a demonstration.  Five liquids were poured into the glass.  Do you see all of the liquids mixed together?  Why not?

Different liquids have different densities?  What does that mean?  Corn syrup is the liquid with the highest density and it sat at the bottom and would not mix with the other liquids that were poured on top of it.  Next came water that we mixed with food colouring. We then poured on cooking oil.  These three liquids sat on top of each other.  The fourth liquid was vinegar.  Because vinegar and water look almost the same, we were sure that we could see the fourth layer BUT, when we poured the vinegar on, it slipped below the oil and mixed with the water.  Can you tell why this happened?  Finally we added green dish washing liquid.  Again we thought it would form a fourth layer on top, but it slipped below the oil and the water/vinegar mixture and sat on top of the corn syrup.  Which liquid had the lightest density?  Why did the water and vinegar mix?  Why did the dish soap go below the water?  Scientists ask questions.  We do too!