Topic 5- Solids, Liquids and Gases Flashcards
how do you calculate density?
mass/volume
how do you calculate the density of an object?
1) weigh the mass of the object on an electric balance.
2) find its volume: liquid by measuring cylinder or solid (place in water and measure the displacement)
3) use the formula density= mass/ volume to work out the object’s density.
how do you calculate pressure?
force (N) /area (m^2)
what is the pressure of a fluid like?
pressure at a point in a fluid that is at rest acts equally in all directions.
how do you calculate pressure difference?
height X density X g
what happens when a solid melts into a liquid and why/
when a solid is heated, its atoms vibrate faster about their fixed points until eventually it melts into a liquid. This happens because the particles have gained enough energy to make them vibrate until the forces between them are overcome.
what happens when a liquid boils?
A liquid boils because the heat energy supplied makes the particles gain kinetic energy and move faster. Eventually, when enough of the particles have enough energy to overcome their attraction to each other.
what happens when a liquid evaporates?
when a liquid is evaporating, it is because the particles are escaping from the liquid to become a gas. It can occur at temperatures lower than the liquid’s boiling point as long as:
1) It is travelling in the right direction to escape the liquid
2) the particles have enough KE.
what happens to the average temperature of the liquid after evaporation and why?
the fastest particles are most likely to evaporate from the liquid, so when they do, the average KE of the remaining particles decrease. This decrease in temperature means that the average particle energy decreases and the liquid cools.
how are particles in a solid arranged?
- strong forces of attraction
- particles are packed closely together in a fixed regular arrangement.
- do not have much energy, so they vibrate very little.
how are particles in a liquid arranged?
- weaker forces of attraction than in solids.
- particles are packed closely together but are irregularly arranged.
- move in random directions but a low speeds.
how are particles in a gas arranged?
- almost no forces of attraction
- particles are free to move
- travel at high speeds in random directions.
what is Brownian Motion
Brownian Motion is a principle that particles of different sizes are constantly moving around in random directions. It supports the Particle Theory.
give an example of Brownian Motion
smoke.
large heavy particles (e.g. smoke) can be moved by smaller and lighter particles (e.g. air) that are travelling at high speeds.
Explain why gas molecules exert a pressure at all times?
They have a random motion and so when they collide with each other, they hit the walls of the container. When they hit the wall, they are exerting a force and this force applied over an area creates pressure.
what happens if we heat or cool something?
if you heat something, they gain energy and move faster.
if you cool something, it loses energy and moves slower.
what happens at Absolute Zero and what temperature is it?
At -273 degrees Celsius, atoms have the smallest amount of kinetic energy possible.
how do you convert from degrees to kelvin, or from kelvin to degrees?
kelvin—> degrees : -273
degrees—> kelvin : +273
what does an increase in temperature mean?
an increase in temperature means an increase in the average speed of gas molecules
how is the average kinetic energy of a gas related to its kelvin temperature?
the average kinetic energy of a fixed mass of gas is proportional to the average kinetic energy of its molecules.
what is the pressure law?
the pressure of a fixed mass of gas is proportional to its absolute temperature provided that the volume remains constant.
(this is because as the temperature of the gas in a sealed container increases, they have more kinetic energy. This means that they collide more often and hit the walls of the container more= pressure)
what equation supports the pressure law?
P1/T1 = P2/T2
what is Boyle’s Law?
the pressure of a fixed mass of gas is inversely proportional to its volume provided that the temperature has remained constant.
what equation supports Boyle’s Law?
P1V1 = P2V2
