P3
Density
Required Practical: find the density of an irregular shaped object
Liquids
Gases
Solids
Particles are close together, arranged in a regular pattern and vibrate around a fixed point
particles are close together, are not in a regular pattern and are randomly arranged, the particles move to fill the container they’re within
Particles move in random directions at random speeds, are very far apart and not arranged in any pattern
Density - mass for a given volume
Density (kg/m^3) = Mass (kg) / Volume (m^3)
ρ = m/v
High density
High density
Low density
when an object is placed in water, the volume of water displaced is equal to the volume of the object
Method:
Find the mass of the object using an electronic scale,
Fill the eureka to below the spout,
Put a measuring cylinder underneath the spout to collect the water,
Place the object into the can gently,
Measure the volume of the water that was split into the measuring cylinder
Figure out the density by using the equation Density = Mass/volume
Measure mass first as water can change the mass
Internal energy
Changes of state
Solid
Gas
Liquid
Melting
Evaporating
Sublimation (rare)
The total kinetic energy and potential energy of the particles in an object.
Total energy within the particles.
If you heat a substance you increase its internal energy
If you decrease the heat of a substance you decrease the internal energy
Changes of state
When a substance is heated, energy is transferred to the particles into the kinetic energy stores of the particles, so they move faster. Temperature is proportional to the average kinetic energy of the particles within a substance.
Specific heat capacity
The amount of energy required to raise the temperature of 1kg of a substance by 1°C
Change in thermal enegy (J) = mass (kg) x specific heat capacity (J/kg) x change in temperature (°C)
∆E =mc∆θ
Specific Latent heat
The amount of energy required to change the state of 1kg of a substance.
Specific latent heat of vaporisation
Specific latent heat of fusion
The energy needed to turn 1kg of a Solid into a liquid
The energy needed to turn 1kg of a Liquid into gas
Energy (J) = Mass (kg) x Specific Latent Heat (J/kg)
E=mL
Heating and cooling graphs
As the line goes up it shows the temperature is rising
As the line plateaus it changes state
Melting point
Boiling Point
Particle motion in gases and pressure
When a gas particle collides with a surface they exert a force on it. This causes pressure within the container.
Gases move at random speeds in random directions
Increase pressure by
Decrease volume in container
Increase number of gas particles
Increasing temperature
Pressure x Volume = Constant
pV=k
As they are heated higher kinetic energy so more collisions
The random motion of tiny particles in a fluid is called Brownian motion
Less volume to move so more collisions
More collisions as more particles
Temperature is a measure of the average kinetic energy of particles in a substance.