Chapter+2+Changes

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BC Bitesize: Revise the particle model - Review with the particle model activity =====

**Diffusion :**
====__Particles__ in __liquids and gases__ move about randomly (called Brownian motion) all the time. Particles __spread out__ in liquids and gases until evenly mixed. This process is called __diffusion__. This means substances __diffuse__ from areas of high concentration to areas of low concentration.====

Brownian motion
The random movement of the small particle(s) is called Brownian motion.

Virtual simulation echalk This diffusion simulation shows how some large particles dissolve and eventually spread out due to collisions between themselves and the surrounding smaller particles.

3. Solid - XXX

 * Diagrams of Ammonia and Hydrochloric acid**



echalk part:main lesson
 * Potassium manganate in water**: Diffusion is caused by particles moving amongst each other to become evenly mixed.
 * Bromine gas in air and a vacuum**: Particles move far more quickly through a vacuum than through air because there are no particles to get in the way.
 * Hydrochloric acid and ammonia**: Some particles are lighter than others. Light particles diffuse more quickly than heavy ones.

A substance can be more dense for two reasons:
1. Particles could have a greater mass 2. Particles could be closer together

In gases the collisions of the gas particles with the container cause PRESSURE. Pressure increases if:
1. There are more particles 2. The particles move faster