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Patty wears a lot of perfume. As her body heat warms up the perfume small particles leave her skin and bounce around with the gas particles that make up the air.
The perfume particles behave in the same way as a gas: they are constantly moving. Near Patty the perfume particles are more concentrated (there are more of them) but the particles soon diffuse away from her and become less concentrated (there are less of them).
Remember, Patty would have put liquid perfume onto her skin - but her body heat will cause the the perfume to change state to form a gas ... which is what you smell.
When you put some milk in a cup of coffee the two liquids don't stay separate - they mix together to form a light brown liquid
The particles of milk and the particles of coffee are both constantly moving around and bump into each other all the time. As they move about the milk particles start to travel around the coffee cup and the coffee particles do the same.
The hotter the coffee is the quicker the particles will mix together - this is because the hotter particles will have more energy and will move around more than cooler ones.