Matter Is Made of Particles

Activities to try

1. 1

   Why we believe in particles: a three-phenomenon bench

   Why it works: We accept invisible particles because one idea — tiny, moving particles with empty space between them — explains three otherwise puzzling observations (compressibility, a mixed volume less than the sum of the parts, diffusion). The model is inferred from evidence, not seen.

   1. Push a sealed gas syringe with a blocked nozzle and notice it compresses surprisingly far; predict first whether and why it should squash.
   2. Then examine (or toggle to) a particle view: the plunger moves because widely-spaced particles close the empty gaps between them.
   3. Mix 50 ml water with 50 ml alcohol (e.g. methylated spirit handled by an adult) in a measuring cylinder, or dissolve salt in a measured volume of water, and observe that the combined volume is a little less than the expected total; predict the final level and WHY beforehand.
   4. Zoom to the particle view: smaller particles tuck into the spaces between larger particles, so less volume is added than expected.
   5. Release a scent in one corner and track how long it takes to reach the far side, noting that in a real room draughts and air currents also help carry it; zoom in to see the scent particles moving, drifting and mixing among the air particles. For a slower view without draughts, watch a drop of food colouring spread in still water.
2. 2

   Zoom into a block: feeling the too-small-to-see scale

   Why it works: All matter — including a solid metal bar and invisible gas — is made of enormous numbers of particles far too small to see; the three states differ in how those particles are arranged and spaced.

   1. Start from an everyday object — a block of metal, a cup of water, or a sealed jar that contains air — and use a tap-to-reveal or zoom to move from the whole object down to the particles it is made of; note that the air, though unseen, is also made of particles.
   2. For each state, read a short flap explaining the arrangement: particles packed closely in a regular pattern, vibrating in fixed positions (solid); still close together but irregularly arranged and able to slide past each other (liquid); spread far apart and moving freely in all directions (gas).
   3. Describe aloud roughly how much smaller than the object a single particle is, to register that particles are too small to see.
3. 3

   Do properties belong to one particle or to the many? (predict, then explain, with probes)

   Why it works: Properties like colour, hardness and state are bulk properties that emerge from how huge numbers of particles are arranged and held together — they are not stamped on each individual particle. The gaps between particles are empty, not filled with air or more material.

   1. Consider a single particle of copper on its own: predict whether it is orange, hard and shiny like the whole bar, and explain WHY before any reveal.
   2. Answer the probing questions: What is in the space between two copper particles? Is a single water particle wet and runny? If the bar were ice instead, is one ice particle cold?
   3. State where the bar's colour, hardness and state actually come from if not from each particle.