P6: Molecules and Matter Flashcards
Definition of density?
The mass per unit of a material
How to calculate density?
Density = mass/volume
State the different states of matter?
Gas
Liquid solid
Describe the particle arrangement of a solid?
Tightly packed in a regular arrangement. Particles can only vibrate on the spot
Describe th particle arrangement of a liquid?
Close together, but with an irregular arrangement. They can flow over each other
Describe the particle arrangement of a gas?
Seperated, with no regular arrangemnt. Particles can move freely
What is always conserved when a substance undergoes a change of state?
Mass
How does a change of state differ from a chemical change?
In a change of state, the material can return to having its previous properties if the change is reversed
What is sublimation?
When a solid changes into a gas without passing through a liquid state
What is evaporation?
When a liquid changes into a gas state
What is the opposite of evaporation?
Condensation, which is when a gas changes into a liquid state
When water boils in an open pan, why does the mass of the pan of water appear to decrease?
Some of the water will evaporate and turn into water vapour. This will leave the pan meaning the mass of the pan will decrease. The mass of the whole system however remains constant
Explain the processes involved when a bathroom mirror mists up?
Hit water evaporates to form water vapour
This water vapour lands on the cooler mirror
The vapour fondensed and returns to liquid state on the mirror’s surface
What is the internal energy of a substance?
The energy stored by the particles
The sum of the total kinetic and potential energies that make up the system
How does heating affect the energy of a substance?
Heating transfers energy to the substance
It increases the energy of the particles that meake up the substance
What 2 things can heating a substance do?
Raise its temperature
Change the state of the substance
What theee factors determine the temperature change of a system?
Mass of substance being heated
Type of material
Energy inputted into the system
Describe how the internal energy and temperature of a substance changes when a change of state occurs?
The internal energy of the substance will be increased or decreased
The temperature of the substance will remain constant
Define specific latent heat?
The amount of energy needed to change the state of 1kg of a substance with no change in temperature
State the equation for the energy required to change state?
Energy to change state = mass x specific latent heat
What is the specific latent heat of fusion?
The energy required to change 1kg of a substance from solid state to liquid state without a change in temperature
What is the specific latent heat of vaporisation?
The energy required to change 1kg of a substance from liquid state to gas state without a chanege in temperature
Describe the motion of molecules in a gas?
They are in constant random motion
What factor affects the average kinetic energy of gas molecules?
The temperatue of the substsnce
The higher the temperature, the higher average kinetic energy of the molecules
What effect does increasing temperature have on the pressure of a gas when held st constsnt volume?
Pressure of the gas will increase as the temperature increases
Why does pressure increase as temperature increases?
Kinetic energy of molecules increases
Collisions between molecules becomes more frequent
Greater rate of change of momentum
Greater force and therefore pressure
Describe the force that the pressure of a gas exerts on the walls of its container?
Thd net force acts at right-angles to the containers surface
The force increases as pressure increases
What can be said about the product of pressure and volume for a fixed mass of gas at constant temperature?
It is constant
p V = constant
What is the unit for pressure?
Pascal (Pa)
What increases when you do work on a gas?
The internal energy of the gas
This cam also lead to an increase of temperature
Why does the temperature of air inside a bike pump increase when it is pumped?
Work is done on a gas when it is compressed
Doing work on a gas increases its internal energy, so also increases the average kinetic energy of the molecules
Temperature increases with an increase of average kinetic energy
