P1 - Matter Flashcards
What was Dalton’s model?
- A very small indestructible sphere
- he believed that different elements contained different types of atoms and all the atoms in 1 element were the same
What was J. J Thomson’s model?
- He figured out that atoms weren’t solid spheres
- He discovered electrons
- His model is called the ‘plum pudding model’ with discrete electrons in spread out positive mass
What was the experiment that J. J Thomson carried out that led him to his theory? (extra)
- He was investigating rays given out by hot metals called cathode rays
- He discovered that cathode rays are made of particles less than one thousandth of the mass of a hydrogen atom
- He found a particle which he called an electron that must have come from inside an atom
- He worked out that the charge on an electron is negative
- Thomson thought that part of an atom must be positive as overall, the charge on an atom is neutral
What was the experiment Rutherford carried out that caused him to form his model?
- He fired positive alpha particles at an extremely thin sheet of gold foil
- He expected all of them to pass straight through, but instead, some of them were deflected to the left and right, and some even deflected backwards
What did Rutherford’s experiment prove?
- It proved that the plum pudding model was wrong because the positive mass couldn’t be spread out and instead had to be concentrated in order for the atom to be deflected
What was Rutherford’s model?
- He came up with the theory of the nuclear atom –> he suggested that atoms were made up of tiny, positively charged nuclei surrounded by a ‘cloud’ of negative electrons
What was the problem with Rutherford’s model?
- If electrons were surrounding the nucleus in a ‘cloud’, they would be attracted to the nucleus and cause the atom to collapse
What is Bohr’s model?
- He introduced electron shells and suggested that electrons can only move in a fixed orbit
–> this would provide a reason as to why the electrons don’t rush in towards the nucleus and cause the atom to collapse
How big is an atom’s diameter?
1 x 10 to the power of -10 m
Why is a substance denser as a solid than as liquid or gas?
In 1cm cubed of a solid substance, there are many more particles than in 1cm cubed of that same substance as a liquid or gas
- The mass is greater so the density is also greater
If you have 2 different sized blocks of the same element the density of the blocks are ___ because ___
the same because density is a property belonging to the material and not of the object
What is the conservation of mass?
- You have to add or remove material for the mass of a system to change
- Particles don’t appear or disappear
- For example, if 1g of ice melts then 1g of water will be made
What are physical changes and are they easy to reverse?
Physical changes are changes in which new substances are not made and the particles are just rearranged, like in a change of state
- They’re easily reversible
What are chemical changes and are they easy to reverse?
Chemical changes involve atoms from the reactants breaking and joining in a different way to form new substances
- They are either hard to reverse or irreversible
What is the definition of specific heat capacity?
The energy needed to raise the temperature of 1kg of a material by 1 degree
Solid to gas is called ___ and gas to solid is called ___
subliming and deposition
When a substance is changing state, the temperature ___
remains constant
What does the energy provided do when a substance is changing state?
- Increases internal energy
- Energy used to break / join attractive forces between molecules
What is the specific latent heat of fusion?
The energy transferred when 1kg of a substance changes from the solid state into the liquid state or from the liquid state into the solid state
What is the specific latent heat of vaporisation?
The energy transferred when 1kg of a substance changes from liquid to gas
How does temperature affect gas pressure?
- If the temperature of a gas increases, the gas particles have a higher average speed
- This means they collide more frequently with the sides of the container
- These collisions produce a bigger force over a certain area which produces a bigger pressure
What is the relationship between volume and pressure?
Pressure and volume are inversely proportional
- Volume halves, pressure doubles
- Volume doubles, pressure halves
Why are pressure and volume inversely proportional?
- The collisions of the gas particles produce forces at right angles to the surface
- If you halve the volume, you double the number of collisions per second between the gas particles and the container
What is the equation realating pressure and volume?
Pressure (Pa) x volume (m cubed) = constant
How does doing work on a gas affect temperature in terms of using a bicycle pump?
- If you apply a force to the pump, the average speed of the particles will increase because their kinetic energy increases when they collide with the moving piston –> so the temperature is higher
What are the 2 ways in which you can increase the internal energy of a gas?
- Heating it
- Doing work on it
What is atmospheric pressure?
- The gases of the atmosphere exert a pressure called atmospheric pressure
On the surface of the Earth, atmospheric pressure is around ___ Pa which means that there’s a force of around ___ N on each square metre of the Earth’s surface (which is the weight of 10 cars)
100,000 Pa
100,000 N
Why does a can collapse if you take the air out of it and why does it keep its shape when it contains air?
- When you have an open can, the forces on the can are equal in all directions so the shape doesn’t change
- If you pump the air out, the can collapses because the atmospheric pressure is bigger than the pressure inside the can
What happens to atmospheric pressure as you go up?
- As you go up, atmospheric pressure decreases because there is less air above pushing down
What is liquid pressure and what do water molecules collide with?
- Water in an ocean exerts a liquid pressure
- Water molecules are very close together and so collide with each other, the container and anything in the water
In which direction does liquid pressure act in?
All directions
What happens to liquid pressure as you go deeper?
- The deeper you are, the higher the liquid pressure is as there is more water pushing down on you
What happens to pressure in liquids of different densities?
- The pressure at a particular depth will always be greater in the denser liquid
- This is because the denser the liquid is, the greater the weight of particles pushing down is
Why is there an upwards force / upthrust on a floating object?
- Anything that’s floating must have an upwards force on it to balance its weight
- When you are floating on the surface of a swimming pool, you are in contact with the water and the air
–> the water exerts a bigger upwards force on you than the downwards force exerted by the air (net force is upwards)
Why do some objects float and others sink?
If the pressure difference x area is big enough, the net force will be enough to balance the weight
