Solids = particles are arranged in a regular way close together. Can vibrate about a fixed position. They have a fixed shape.
Liquid = Particles are still together. Can move between and past each other, in a random jostling manner. Some are touching. They flow to take the shape the container they are in.
Gas = Particles are much, much further apart. They move more rapidly than in liquids. Random motion of the particles. Gases expand to fill the container they are in.
Definition of air pressure or how do air/gas particles cause pressure?
The gas particles collide with the container walls exerting a force. Pressure is the force per unit area.
Absolute zero and the Kelvin scale
Absolute zero is the lowest temperature that can be theoretically reached. There can be no lower temperature as the particles cannot do less than not move at all.
To convert degrees Celsius to degrees Kelvin we add 273.
To convert degrees Kelvin to degrees Celsius we subtract 273.
Law of Pressure
Write the equation: P1 / T1 = P2 / T2
Rearrange the equation : T2 x P1/T1 = P2
Pressure and Volume
Write out the equation: P1V1 = P2V2
Rearrange the equation: P1V1/P2 = V2
Remember this is at constant temperature and fixed mass
Average Speed
Average speed is measured in meters per second. Average speed is calculated by dividing the total distance travelled by the total time taken.
Average speed = distance/time
Distance/Time Graphs
On a distance time graph a straight line indicates constant speed. A flat line means the object has stopped. A smooth curve shows a steady increase in speed.
Acceleration
If an object is increasing in speed as it travels we say that it is accelerating. If it decreases its speed we say that it is decelerating.
Acceleration = change in velocity / time taken
A = (v- u) t
A = acceleration
v = final velocity
u = inicial velocity
t = time in seconds
Scalar and Vector Quantities
Force is a vector quantity as is velocity, acceleration and weight. They all have direction as well as size with a unit. Speed, temperature and mass are scalar quantities; these only have a size not a direction. To fully describe a force you have to state the size and direction.
Friction
Friction is a force that slows/stops motion between touching surfaces. Friction reduces with speed. It acts against the direction of movement. Air resistance of an accelerating object increases until it balances the driving force and the object stops accelerating. Friction converts kinetic energy to heat energy. It also causes wear on the surfaces which are in contact. This can be reduced by lubrication.