Too small to see: the evidence for particles

We are learning to use observations as evidence for a model of matter made of tiny moving particles with empty space between them.

Before you startAbout 60 minutes · what success looks like · notes for the helper

About 60 minutes. It's fine to stop after the Quick Check and come back another day: the lesson opens where you left it, at the Quick Check.

You'll know you've got it when

I can state the main ideas of the particle model: matter is made of particles, the particles are always moving, and there is empty space between them
I can explain an observation twice, once with a 'continuous stuff' model and once with a particle model, and say which fits the evidence better and why
I can draw a labelled particle diagram of liquid water showing the particles, the empty space between them and arrows for their motion

For the helperhow to sit beside this lesson, and what this step is for

This step: Spark

Start with the question at the top and chat about it. There is no wrong answer here: it gets your learner thinking about what they already know.

Getting ready: A clear glass of water left still for a few minutes, a bottle of food colouring (a dropper or a bottle nozzle is fine), a sheet of white paper to stand the glass on, and an orange to peel at the far end of a room, or a crushed mint leaf if anyone reacts to citrus. A few sheets of paper and a pencil for the diagrams.
What understanding sounds like: Listen for your young person giving a reason that mentions movement, such as 'the water particles keep bumping the colour along', rather than 'it just spreads out'. A prediction that gets revised after the glass is watched is just what the lesson is after.
A likely mix-up, and something that helps: The likeliest slip is drawing particles as tiny drops or as blobs floating in blue water, with the water itself still drawn as smooth stuff. You might ask, 'What is in the gap between two of your particles?' The answer to look for is nothing at all, which can feel strange, so it is fine to let the question sit.
If it comes easily: If it comes easily, you might ask them to invent a third observation that a continuous model would struggle with, and to test their own idea on you. One way is to ask what extra rule the continuous model would need to explain it, and whether the particle model needed that rule.
If it's a struggle: If it is a struggle, one way is to watch the glass together first and write down only what can be seen, before any model comes in. Then add one model at a time and talk through the diagram before drawing it. 'Model', 'particle' and 'continuous' carry this lesson, so for a learner still building English it can help to say them in the home language too, with a finger on the glass. If your young person shuts down, the glass itself, watched and described in their own words, is a real start, and the models can wait for another day.

Step 1 of 6 · Spark

Lesson 1 of 5 · What Everything Is Made Of: Particles on the Move

Still water, moving colour

For the helper

Start with the question at the top and chat about it. There is no wrong answer here: it gets your learner thinking about what they already know.

Stand a clear glass of water on a sheet of white paper and let it sit still for a couple of minutes so that nothing in it is moving. Now touch the nozzle of the food colouring to the surface and let ONE drop slide in. Do not stir, do not shake, do not breathe on it. Before you read on, write down a prediction: what will the glass look like after 10 minutes, and why? Then leave it where you can see it. Keep your prediction and look again at the end of the lesson. A second observation comes later in this lesson: peel an orange at the far end of a room and notice when the people at the other end first smell it.

One drop, no stirring. What is moving the colour, when nothing is moving the water?