Diffusion in gases
2 marks · HardExplain why, when perfume is sprayed in one corner of a large room, the scent is eventually noticed everywhere in the room. Include reference to the movement of gas particles.
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Also accept: Perfume particles move randomly and spread throughout the air by diffusion, from an area of high concentration to everywhere in the room.; Perfume particles move in all directions, colliding and gradually spreading from where the concentration is high, until they are detected across the whole room.
Common mistakes: Saying scent is carried instantly.; Not mentioning random movement/diffusion/high to low concentration.
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Marking points
M1 · 1 mark · States particles move randomly/in all directions, or spread by diffusion.
A1 · 1 mark · Explains that particles move from high to low concentration/spread throughout the room
Worked solution
Perfume particles move randomly in all directions when sprayed. They spread out by diffusion from where the concentration is highest (the corner) until they are evenly mixed throughout the room and can be smelled everywhere.