Classification of Matter- Diffusion
5 Minutes
Diffusion for kids: learn how particles mix across solids, liquids, and gases and what speeds up diffusion. A science lesson in English.
- How ink spreads through water to show what diffusion is
- How kinetic energy, stirring, and heat speed up diffusion
- Diffusion in gases, liquids, and solids like chalk on a board
What this lesson teaches
Diffusion is the process in which the tiny particles of one substance mix into another substance by settling into the gaps between its particles. These particles naturally travel from a region of higher concentration, where there are many particles gathered together, to a region of lower concentration, where there are fewer particles, until the whole mixture is evenly distributed.
How particles move and spread
Every substance is made of tiny particles that have empty spaces between them. When ink is poured into water at one spot, the ink particles collide with the randomly moving water particles in a process called Brownian motion. These particles move about using kinetic energy, which is the energy possessed by moving particles. When a substance has more kinetic energy, its particles move faster and collide more often, causing the rate of diffusion to increase.
Factors that speed up diffusion
- Stirring a liquid provides mechanical energy from the hand, which transforms into kinetic energy for the liquid particles and makes them mix together quickly.
- Raising the temperature of a substance increases the kinetic energy of its particles, causing them to move much faster.
- Pouring ink into hot water causes the particles to collide rapidly and diffuse much faster on their own without any stirring.
Diffusion in gases, liquids, and solids
- In gases, particles move very fast and randomly, so diffusion happens fastest, allowing the aroma of cooking mutton curry or sprayed scent to spread quickly across a room or down a street.
- In liquids, particles move randomly but remain closer together than in gases, causing diffusion to happen more slowly, such as when milk mixes into water.
- In solids, particles do not move around freely and only vibrate lightly in the same place, making diffusion occur at an extremely slow pace.
- Chalk marks left on a blackboard over a long school holiday become difficult to erase because the solid chalk particles slowly diffuse into the blackboard over time.