P6 Molecules and Matter Flashcards
What is density?
Density describes how closely packed the particles are in a solid, liquis or gas.
How do you find density?
Denisty = Mass / Volume
What is the scientific unit of density?
Kg/m^3
What is internal energy?
It is the total of kinetic energy and potential energy of all the particles in an object.
What is potential energy?
Energy due to the indiviudal postions of a particle relative to another
What is the density of water?
1000 kg/m^3
What happens to the mass of a substance when it changes state?
It stays the same as number of particles don’t change
What is required to melt a solid and boil a liquid?
Energy
What is the difference between boiling and evaporating?
During evaporation particles only leave from the surface of the liquid whereas in boiling bubbles of gas are formed throughout the liquid.
What do the flat sections of a temperature-time graph show?
Melting and boiling point
Why does temperature remain constant at the boiling/melting point when the internal energy is increasing?
There is a change of state occuring here so potential energy increases but kinetic energy remains constant
What is the specfic latent heat of a substance?
The amount of energy required to melt or boil 1Kg of a substance
What is specific latent heat of fusion?
The amount of energy required to change the state of 1Kg of a substance from a solid to a liquid
-in joules
What is specific latent heat of vapourisation?
The amount of energy required to change the state of 1Kg of a substance from a liquid to a vapour.
-in joules
How do you calculate the specific latent heat of a substance?
Specifc latent heat = energy (j) / mass (kg)
What determines the state of a substance?
The strength of the forces of attraction.
When a substance is heated ….
- if the temperature rises, the kinetic energy of the particles increase
- if it melts or boils, the potential energy of the particles increase
What causes the pressure of gas on a surface?
Particles of gas repeatedly hitting the surface.
How can the specifc latent heat of ice (or water) be measured?
By using a low-volatge heater to melt the ice (or boil the water)
Why does the pressure of gas increase if the temperature is increasing in a sealed container?
the molecules move faster so they hit the surfaces with more force
What can be used as evidence of the random motion of gas molecules?
The unpredictable motion of smoke.
How do you find the density of an irregular object?
1) Measure the mass on a balance
2) Fill a Eureka can with water up to it’s spout
3) Slowly place the object into the water
4) Collect and measure the volume of water displaced using a measuring cylinder
5) The volume displaced is equal to the volume of the rock
density = mass / volume
How do you find the density of a regular object?
1) Measure it’s mass on a balance
2) Measure it’s volume using a vernier calliper
3) Denisty = mass / volume
How do you measure the denisty of a liquid?
1) Place a beaker onto a balance and zero the balance
2) Pour 10ml (10cm^3) into the beaker
3) Measure the mass of it
Density = mass / volume
(note : larger the volume the more accurate density is)