In 400 BC the Greek philosopher Democritus wondered if matter might be 'lumpy'. The philosophers called these lumps "atoms", which means uncuttable in the Greek language. This would mean that when we cut a lump of something enough times, we would cut down to a single lump- an atom- and we could not cut that.
This video shows how the world is made of 92 types of incredibly small partiles called atoms. You will learn the names and find out how they are different to each other. You will also find out what we call a substance made of only one kind of atom.
Gas race to the ceiling: If the hydrogen-filled balloon and helium-filled balloons are filled to the same size, the hydrogen should "win the race" to the ceiling if they are released at the same time from the floor as the density of hydrogen gas is half that of helium.
Ask students which variables need to be controlled in order to make this race a "fair test". Answer: The weight and size (diameter) of the balloons. Which variable is independent i.e. which one are we controlling? Answer: Height or length of balloon race. Which variable is dependent i.e. which one are we not controlling? Answer: time, or which balloon wins the race.
You should test this demonstration beforehand to ensure the hydrogen is a clear winner, even though the time difference could be small.
The students should arrive at the conclusion that hydrogen has the lighter atoms, thus justifying its Number 1 position.
This demonstration is fun, and can generate excitement amongst the students.