P6 - Molecules and Matter - Complete Flashcards
What is the Density equation?
Density = mass/volume (in kg/m3)
What precaution would one have to take when measuring the density of a liquid? (When weighing it)
To subtract the weight of the measuring cylinder from the end mass
What is the density of pure water?
1000kg/m3
If an object’s density is higher than that of water, what will it do?
Sink
If an object’s density is lower than that of water, what will it do?
Float
What is liquid to gas called?
Evaporation
What is gas to liquid called?
Condensation
What is solid to liquid called?
Melting
What is liquid to solid called?
Freezing
Explain, using the Kinetic Theory of Matter, the particles in a solid.
They are held in fixed positions next to each other and are the least energetic of the states of matter
What does the conservation of mass mean?
In a closed system, the mass of a substance before and after changing state is the same
Explain, using the Kinetic Theory of Matter, the particles in a liquid.
They move about at random and are in contact with each other, they are more energetic than the particles in a solid
Explain, using the Kinetic Theory of Matter, the particles in a gas.
They move about at random, they are extremely far apart, and it is the most energetic of the states
Where does evaporation occur?
Only on the surface of the solution being heated
What does the flat section on a temperature-time graph show?
The ealing point or the boiling point of the substance
What is latent heat?
The energy transferred to a substance when it changes state. This is not expressed in its temperature as it is going towards making the change
What is the internal energy of a substance?
The total energy in its kinetic and potential energy stores. It does not include the gravitational potential energy its has or the kinetic energy of the whole substance moving one way or another
The —– of the —— of —— between particles of a substance explains why it is a solid, liquid or gas
The strength of the forces of attraction between particles of a substance explains why it is a solid liquid or gas
When a liquid is heated, what happens to the particles at the surface?
Once they have gained enough energy, they move away almost completely from the surface and are a gas above it. The forces of attraction are so weak that they can barely hold it above the liquid
In terms of energy, what happens to a substance when it is heated?
Its kinetic energy increases as it heats up, and if it melts or boils the potential energy of its particles increases
What is pressure from a gas caused by?
Particles of a gas hitting a surface
What is the equation for the specific latent heat of fusion/vaporisation?
Energy, E, (J)/Mass, m (kg) = specific latent heat of fusion/ vaporisation
What is the specific latent heat of vaporisation?
The energy needed to change the state of 1kg of the substance from liquid to vapour, at its boiling point, (without changing its temperature)
What is the specific latent heat of fusion?
The energy needed to change the state of 1kg of a substance from a solid to a liquid at its melting point (without changing its temperature)
What does the flat part in a temperature/time graph represent?
The substance changing state. The temperature does not increase as the substance needs the energy to change state and break its intermolecular attractions
What correlation is their between heating air molecules and pressure?
As the air molecules are heated, they exert more pressure on the objects around them
Why does heating increase pressure?
Heating increases pressure because the air particles receive more kinetic energy, causing them to bounce off the objects around them more frequently, and the force with which the bounce off the objects is increased as their velocity is increased
What is evidence for the random motion of gas particles?
The unpredictable motion of smoke in a closed environment as the gas particles bounce off the larger smoke particles and so it is constantly moving direction
How can you compress or expand a gas?
By instituting pressure changes
What would compressing a gas do to its temperature if not done slowly?
Increase it, as the work done needed to overcome the pressure of the gas to compress it would be transferred to the gas - therefore heating it up
Why does the pressure increase if you reduce the volume of a fixed mass of gas and increase its temperature?
As: the space the molecules move in is smaller, so they don’t travel as far in between collisions with each other and the surroundings, and so impacts per square meter increases, and the the impact pressure increases
What equation links pressure and volume?
Pressure, p (Pa) x Volume, V (m3) = Constant, this applies only to when the gas’s temperature and mass odes not change
