[4] Kinetic Theory Flashcards
What does Kinetic Theory predict about the molecular behaviour of solids?
Kinetic Theory predicts that in solids the molecules are close together and are acted on by both attractive and repulsive forces. These forces cancel each other out causing the molecules to vibrate about a fixed point. As they are not free to roam around, solids have definite shapes.
What does Kinetic Theory predict about the molecular behaviour of liquids?
In liquids the molecules are further apart than they are in solids. They also vibrate but can in addition slip past each other like marbles rocking in a tilted tray. They are never near another molecule long enough to get trapped in a regular pattern. For that reason the liquid can flow and will take on the shape of its container.
What does Kinetic Theory predict about the molecular behaviour of gases?
The molecules in gases are much further apart than in solids or liquids. As a result of this they are easily compressed as their densities are less.
When viewing Brownian motion in a smoke cell the observer sees many specks of light which are …
Smoke particles in random motion
Using what you know about the compressibility (squeezability) of the different states of matter, explain why air is used to inflate tyres.
Air can take on the shape of an object (e.g. Tyre) and can be compressed into a small volume and allow good contact/friction with the road.
Using what you know about the compressibility (squeezability) of the different states of matter, explain why steel is used to make railway lines.
As the tracks are made of a solid, steel, it has a definite shape to allow the train to travel over it.
Explain in terms of molecular behaviour why bromine molecules which travel at about 200 m/s in a vacuum take several minutes to travel 40cm inside a tube of air.
The bromine molecules in a vacuum can travel freely, but in a container with air they are stopped regularly by the air particles.
Solid molecular features
- Solid molecules close together
- Attractive and repulsive forces cancel out and the object vibrates
- Don’t roam around so they have a definite shape
- Examples are steel or Iron
Liquid molecular features
- Molecules are further apart than a solid
- They vibrate but also slip past each other like marbles in a tray
- They are never near another molecule long enough to get trapped in regular motion
Liquid can take on the shape of its container
Gas molecular features
- Much farther apart than in a liquid and solid
- Can be easily compressed since their densities are less
- Molecules move in random motion
