Changing State P1 Flashcards
Define density
The ratio of mass to volume in an object
What is the equation linking density, mass and volume?
Density = mass divided by volume
How do you work out the density of an irregular shaped object?
Weigh your object then place it in a eureka can filled with water, measure how much water comes out using a measuring cylinder to work out its volume then do mass divided by volume to get density
What is the kinetic theory of matter for solids?
Particles held together in a fixed regular arrangement by strong forces of attraction and they vibrate about their position. At low temperatures the vibration is small and can be considered fixed but when a solid gains more energy the particles vibrate more causing neighbouring particles to vibrate. Density is highest at this state as particles are closest together
What is the kinetic theory of matter for liquids?
The intermolecular forces within a liquid are too weak to keep particles in a fixed position so although they are close together they can move past each other and form irregular arrangements. Particles have more energy than when solid but less than when gas and move in random directions at low speeds, they flow to fill the shape of a container. Less dense than solids generally
What is the kinetic theory of matter for gases?
The particles are in a random arrangement and in constant motion as there are almost no forces of attraction between them and the particles are free to move and travel in random directions at high speeds, they fill a volume. They have low densities
What is the process of a solid changing to a liquid?
Melting
What is the process of a liquid to a gas?
Evaporation
What is the process of a gas to liquid?
Condensation
What is the process of a liquid to solid?
Freezing
What is the process of a solid to gas?
Sublimation
What is the process of a gas to solid?
Deposition
Define internal energy
The combined energy of a substance’s kinetic and potential energy
What does a change in state cause a change in?
The potential energy of the particles due to their position, the number of particles does not change they are just arranged differently which means mass is conserved
Why does the temperature remain constant when changing state?
Heat energy is being used to break intermolecular bonds between the particles or form bonds between them rather than to raise the temperature
Define specific heat latent
The heat needed to change 1kg of a substance from one state to another without changing its temperature
What is the equation for specific heat latent?
Lf in J/kg = energy divided by mass
What do the air molecules in a smoke cell do?
Air molecules collide with smoke molecules which pushes them and causes them to constantly move and change direction
Define pressure
A force exerted on a surface which can be thought of as force per unit area (m^2)
What is the equation linking pressure force and area?
Pressure = force divided by area
What happens when a tin of baked beans is heated?
The molecules inside the container gain more energy and start moving with more energy so they collide more frequently and forcefully (because they have a larger momentum) with the surface of the container which increases pressure inside of it. These factors both increase the total force exerted on a unit area
What is the equation linking pressure, volume and constant?
Pressure x Volume = constant
Define constant
The sum of pressure times the volume will remain the same even if the pressure and volume change
What does Boyles Law mean?
For a fixed amount of gas at a fixed temperature, pressure is inversely proportional to volume
What is the relationship between pressure and volume?
Inversely proportional
What happens when you decrease volume of a gas?
Work is done on gas molecules which provides them with kinetic energy so the gas molecules collide with the surface of the pump which increases pressure and transfers energy to the wall of the pump resulting in an increase in temperature
What is the charge of a proton?
1
What is the charge of a neutron?
0
What is the charge of an electron?
-1
What is the size of a proton?
1
What is the size of a neutron?
1
What is the size of an electron?
1/2000
Where are protons and neutrons found?
Nucleus
Where are electrons found?
Shells
Define isotope
Atoms of the same element with the same number of protons but different number of neutrons
What did Rutherford gold experiment involve?
- Shooting a beam of positive alpha particles at a sheet of thin gold foil to see whether they were deflected, most particles went straight through the sheet but some were deflected
What did Rutherford’s experiment prove?
The mass of an atom is concentrated at its centre which has a positive charge however most of the atom is empty space. The positively charged nucleus was surrounded by a cloud of negative electrons
How do you calculate an uncertainty?
Minus the lowest value from the highest value in your table and divide the answer by 2 (work out the range of ur results and divide this answer by 2)
Why could it be dangerous if the temperature of air inside a canister increases by a large amount?
Increasing the temperature increases pressure meaning the canister could explode
How do you work out density of a liquid? 5 steps
Place a measuring cylinder on a balance and zero the balance, pour 10ml of liquid into the measuring cylinder and record the liquid’s mass, pour another 10ml and record total volume and mass, repeat process until measuring cylinder is full, for each measurement use the formula to find density, take an average of calculated densities to get an accurate value for density of the liquid
How is energy stored in a system?
Particles inside a system vibrate or move around (they have energy in their kinetic and potential energy stores), internal energy is the total energy of a system’s particles in their kinetic and potential energy stores
What happens when you heat a system?
Energy is transferred to its particles’ kinetic energy stores which increases internal energy and leads to an increase in temperature or change in state. If temperature changes, the size of the change depends on the mass of the substance, its specific heat capacity and energy input
When does a change in state occur?
If a substance is heated enough the particles have enough energy in their kinetic energy stores to break the bonds holding them together
What is the difference between specific heat latent of fusion and specific heat latent of vaporisation?
Specific heat latent of fusion is the specific heat latent for changing between a solid and liquid (melting/freezing) and specific heat latent of vaporisation is the specific heat latent for changing between a liquid and gas (evaporating/condensing)
How do gas particles create pressure?
They move about at high speeds and collide, when they collide they exert a force on it so in a sealed container the outward gas pressure is the total force exerted by all of the particles on a unit area of the container walls
What did John Dalton say about the atom?
In 1804 he agreed with Democritus that matter was made up of tiny spheres that couldn’t be broken up but he said each element was made up of a different type of ‘atom’
What did JJ Thomson say about the atom?
Nearly 100 years after Dalton’s theory was proposed Thomson discovered particles called electrons that could be removed from atoms. Thomson suggested atoms were spheres of positive charge with tiny negative electrons stuck in them like fruit in a plum pudding model
What did Niels Bohr say about the atom?
Electrons orbiting the nucleus do so at certain distances called energy levels but evidence from further experiments changed this nuclear model to have a nucleus made up of a group of particles which all had the same positive charge that added up to the overall charge of the nucleus
What did James Chadwick say about the atom?
In 1932 about 20 years after the idea of a nucleus was accepted he proved existence of neutrons which explained the imbalance between atomic and mass numbers
What is the current model of the atom?
The tiny nucleus makes up most of the mass of the atom which contains positive protons and neutral neutrons, its radius is about 10,000 times smaller than the radius of an atom. The rest of the atom is mostly empty space, negative electrons whizz around the outside of the nucleus really fast which gives the atom the overall size, the radius of an atom is about 1 x 10^-10m
What can electrons in energy levels do?
Move within or sometimes leave the atom. If they gain energy by absorbing EM radiation they move to a higher energy level further from the nucleus but if they release EM radiation they move to a lower energy level closer to the nucleus. Atoms become positively charged ions when electrons leave the atom
What do unstable isotopes do?
Decay into other elements and give out radiation as they try to become more stable, this process is radioactive decay
