Solids Liquids And Gases Flashcards
Kinetic theory of gases
Molecules in a gas container are in constant random motion at high speeds and undergo sudden changes of motion if they collide with other molecules or the container
Browning motion
The random motion of tiny particles in a fluid
Provides evidence that air is made of small particles
This is because when larger particles such as smoke particles or pollen are observed floating in the air,
the larger particles move with random motion and this is a result of the larger particles colliding with smaller particles that are invisible to the naked eye
Collision force
Collisions produce a net force at right angles to the wall of the gas container or any surface
A gas at high pressure has more frequent collisions with the container walls and a greater force
The higher the pressure the higher the force exerted per unit area
Absolute zero
At absolute zero, particles have no thermal energy or kinetic energy, so they can’t exert a force
Point where particles have zero kinetic energy meaning no further energy to extract
since temperature is a measure of this motion, there is no ‘colder’ state beyond this point where particles can move any slower
Absolute zero = 0 Kelvin = -273 c
Temperature and kinetic energy
Heating a system will change the energy stored in a system by increasing the kinetic energy of its particles
This increase in kinetic energy causes temperature of the system to rise or cause a substance to change state
Internal energy of a gas is the sum of the kinetic energy of all the molecules
Pressure law
If the volume of an ideal gas is constant the pressure law is given by
p ∝ T
Can also be written as
(P1/T1) = (P2/T2)
Boyles Law
For a fixed mass of a gas held at a constant temperature, the boyles law formula is
pV = constant
P= pressure in pascals
V volume in cubic centimeters
Can be rewritten as
p1v1 = p2v2
For comparing the pressure and volume before and after a change in gas
Compression and pressure
Compressed- decreases the volume which increases pressure
• particles travel at same speed at before but distance the travel is reduced as container is smaller
• molecules hit the wall more frequently
•this creates an overall larger net force
Expanded- increases volume which decreases pressure
Pressure
The force per unit area (Pa)
P= F / A
The pressure is lower as the area is greater and vice versa
Density
Mass per unit volume (kg/m^3)
P= M / V
Pressure in different directions
Pressure at a point in a gas or liquid at rest acts equally in all directions and causes a force at right angles to any surface.
Pressure in a fluid is created from the movement of particles
Pressure and depth
Pressure beneath a liquid surface increases with depth, the density of the liquid and the gravitational field strength
P = pgh
-Deeper in the fluid, more particles above the point, hence the greater their weight
-fluids with higher density have more particles per unit volume, hence greater weight
-weight depends upon gravitational field strength
Change of state
When a body changes state, energy goes toward making the molecules freer from each other rather than increasing their kinetic energy - the temperature stays constant
When does boiling occur
When molecules in a liquid gain enough energy to break their bonds and become separate molecules - turning into gas
Specific heat capacity
The amount of energy required to raise the temperature of 1kg of a substance by 1c and I measured in (joules per kilogram degree Celsius)
