The Candle at the Door
You will need: A candle.
Here is a simple test you can make of convection currents at work.
When a room is being heated, the hot air in the room always rises and seeks to escape. Meanwhile, cold air is drawn into the room at a low level to fill the area of low pressure created by the rising warm air.
Allow a room to get thoroughly warm. Then open the door a few inches and hold a lighted candle to the top of the partly-opened door. The direction of the flame will indicate that there is a current of air escaping from the room.
Now hold the candle as low as possible at the door opening. The movement of the flame (plus the cold draft which you will feel) will indicate that there is a current of cold air flowing into the room.
Now experiment with the position of the candle flame about midway between these two extremes of distance. With patience you will find a spot where the flame burns steadily, indicating that there are no drafts at this particular position.
Children learn best through doing
Before children can understand a thing, they need experience: seeing, touching, hearing, tasting, smelling; choosing, arranging, putting things together, taking things apart. Experimenting with real things.
Old-time school teaching used only words and the teachers thought children knew something if they could repeat it. Now we know better. To reach practical understanding we do not need to use many words with young children.
Children are clever. They learn a lot, without being taught. The greatest skill - to be able to talk, to communicate is learnt outside school. In the classroom it's the children who need to talk the most. Unfortunately it is the teacher who does most of the talking!