Particles of Matter Are Continuously Moving

Key points

• Particles of matter are continuously moving: they have kinetic energy.
• Their intermixing on their own is diffusion.
• Temperature ↑ → kinetic energy ↑ → particles move faster → diffusion faster.
• Diffusion is fastest in gases, slower in liquids, slowest in solids.

The agarbatti puzzle

The scent particles of a burning agarbatti move on their own into the spaces between air particles and spread to the next room. This intermixing is diffusion.

Cold water vs hot water

Temperature ↑ → kinetic energy ↑ → speed of particles ↑ → diffusion faster

Daily-life examples

• Hot food is smelt from far away; cold food only up close.
• Perfume sprayed in one corner fills the room.
• A crystal of potassium permanganate colours still water by itself.

Try it yourself

Goal: See how temperature changes the speed of particles and how fast an ink drop spreads.

• Set the water temperature with the slider.
• Press Drop ink and watch the particles spread.
• Note the spread after a few seconds.
• Reset, change the temperature and compare.

Open the simulation full screen

Quick quiz

4 questions. Choose an answer for each, then submit to see your score and the explanations.