Particle Model Flashcards
What is the definition of density?
The mass per unit volume of a material
Density = mass / volume
What does state of matter mean?
A form in which matter can exist, based on the particle arrangement in a substance
What are the different states of matter in order of density of atoms?
Gas, liquid and solid
What is the structure of liquids?
The particles have some kinetic energy, they are free to move and can move around in random directions at very slow speeds
What is the movement of particles in a solid?
The particles vibrate around a fixed position as they don’t have enough kinetic energy to move free,y
What is the structure of particles in a gas?
Particles in gas have almost no forces between them therefore they are completely free to move and move at high speeds in random directions
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 the internal energy of a substance?
The energy stored by the particles and the sum of the total kinetic and potential energies that make up the system
What two things can heating a substance do?
Raise its temperature and change the state of the substance
What three factors determine the temperature change of a system?
Mass of substance being heated, type of material and energy inputted into the system
What is sublimation?
When a solid turns directly into a gas
What is the difference between physical and chemical changes in substances?
Physical changes can be reversed and chemical changes cannot be easily reversed
How does heating cause a substance to change state?
Heating matter gives particles more potential energy, this energy is used to break the bonds of attraction leading to a change of star
Why does heating increase the temperature of substances?
It increases the amount of thermal energy in that substance, it also gives the particles more KE meaning they move faster and their temperature increases
What equation could be used to carbon the energy change when a substance is heated?
Energy = mass x specific heat capacity x temperature
What is specific heat capacity?
The amount of energy needed to increases the temperature of 1kg of a substance by 1C
What does specific latent heat mean?
The amount of energy needed to change the state of 1kg of substance with no change in temperature
What equation is for energy required to change state?
Energy = mass x specific latent heat
What is the structure of particles in a gas?
Particles in a gas have almost no forces between them therefore they are completely fre to move and move at high speeds in random directions
What is the pressure of a gas in terms of the motion of particles?
The particles move in random directions, when they collide with the walls of a container they exert a force which acts at a right angle to the container and this causes pressure
What is the equation to calculate pressure?
Pressure = force / area
What factor affects the average KE of gas molecules?
Temperature of the gas and the higher the temperature the higher the average KE of the molecules
What effect does increasing temperature have on the pressure of a gas when held at constant volume?
Gas pressure will increase as the temperature increases
Why does pressure increase as temperature increases?
KE of molecules increases, collisions between molecules becomes more frequent, greater rate of change of momentum and greater force and therefore pressure
What is the force that the pressure of a gas exerts on the walls of its container?
The net force acts at right angles to each surface of the container and the force increases as pressure increases
How does increasing the volume of gas results in a decrease of pressure?
Molecules become more spread out so rate of collisions decreases and rate of change of momentum decreases, and so force exerted on container decreases resulting in a lower pressure
What can be said about the product of pressure and volume for a fixed mass of gas at a constant temperature?
It’s constant
What is the unit used for pressure?
Pascal
What increases when you do work on a gas?
The internal energy of the gas and this can also lead to an increase of temperature
How do you convert between degree Celsius and Kelvin?
Degrees Celsius -> +273 -> Kelvin
What is absolute zero?
-273C, particles have no KE and don’t move
What equation can be used to calculate the pressure/volume for a gas which the mass is fixed and temperature is constant?
P1 x V1 = P2 x V2
Why does the temperature of air inside a bike pump increase when it is pumped?
Work is done on a gas when it’s compressed, doing work on a gas increases it’s internal energy so increases the average KE of the molecules and temperature increases with an increase of average KE
