Solids, Liquids and Gases Flashcards
Describe the spacing, ordering and motion in a liquid.
Particles vibrate with more energy than in a solid, and can move past each other freely, but are still attracted to each other.
Describe the spacing, ordering and motion in a solid.
Particles vibrate slightly about fixed positions in a regular tightly packed lattice.
Describe the spacing, ordering and motion in a gas.
Particles are free to move around with constant, random motion.
Describe an experiment that demonstrates Brownian motion and explain what evidence it gives us.
You can observe a brightly illuminated glass jar filled with smoke under a microscope. The smoke particles will appear as bright specks that move haphazardly in all directions. This provides evidence for molecules in air, and that randomly moving air particles cause the motion in the smoke particles.
Define pressure.
Force per unit area.
Explain pressure exerted by a gas.
When a gas particle collides with a surface, it exerts a force on the surface, and the surface exerts an equal but opposite force on the particle (Newton’s 3rd law). The size of the force can be calculated using Newton’s second law, that force is equal to the rate of change of momentum. Because gas particles are moving randomly, collisions will be spread equally across the whole surface, providing a steady, even force on the surface - pressure.
Define internal energy.
The sum of the random distribution of kinetic and potential energies associated with the molecules of a system.
Describe what happens to a substance as you heat it.
It’s kinetic energy increases, and therefore so does it’s internal energy.
Describe what happens to a substance as it changes state.
It’s internal energy increases, but it’s temperature does not.
Describe the terms: melting, boiling and evaporation.
Without increasing in temperature, the internal and kinetic energies of the substance increase. The velocity of the particles increases, and the move further from their fixed point, allowing them to change state.
