Changes Of State Flashcards
What was daltons model
- small indestructible spheres
- atoms in one element are all the same
- atoms in one type of element are different from atoms in another element
What was Thomson’s model
- plum pudding model, large positive mass with electrons embedded in it
- found electron using cathode ray experiment
- found protons by realising that atoms were of neutral charge, so there had to positive masses cancelling out the electrons negative charge
What was Rutherfords model
- found that the positive charge was not a large Cloud, but a small nucleus, which contained both protons and neutrons
- he realised this when he fired alpha particles at a thin piece of gold foil, and one of them bounced all the way back to where it started, he realised that there was a dense mass in the atoms, that pushed back the alpha particle
What was Bohrs model of the atom
- suggested that electrons could only move in fixed orbits called electron shells
- without them, the electrons would spiral until they hit the nucleus
How big are atoms and molecules
10^-10
Or
1 x 10^-10
Density defenition
Density is a measurement of the amount of a mass of a substance contained in a given volume
What is the formula for density?
Density = Mass / volume
How do you find the density of an irregularly shaped object?
Step one: to find the volume, you need to submerge the shape in water, and measure the water level increases
Step two: to find the mass, use a weighing scale
Step three: use density equals mass divided by volume
What is the difference between heat and temperature
- temperature is the measure of how hot or cold something is, meaning that it can go into negatives
- heat is the measure of thermal energy contained in an object, and cannot be negative, as you cannot have negative energy
What units of measure do you use to measure temperature
- kelvin
- degrees Celsius
To measure heat, you use
- joules
What is the definition of specific heat capacity
Specific heat capacity is the amount of energy needed to raise the temperature of 1Kg of a substance by 1 degree
specific heat capacity equation
Energy = Mass x Specific Heat Capacity x (change in) Temperature
What are the units for specific heat capacity
J/Kg degrees Celsius
What is internal energy
The sum of randomly distributed kinetic and potential energy of all of the particles within an object
Each state and how much kinetic energy they have
Solids - have the least kinetic energy, as their particles dont move around quickly
Liquids - have the highest potential energy
Gases - have the highest kinetic energy, as they move around very quickly
What is specific latent heat
The amount of heat needed to change the state of 1Kg of a substance at a constant temperature
How to calculate the energy required for the specific latent heat
Energy required = mass (kg) x specific latent heat of fusion
Specific latent heat of fusion
The amount of thermal energy required to change the state of 1Kg of a substance from a solid to a liquid at a constant temperature
Specific latent of vaporisation
The amount of thermal energy required to change the state of 1Kg of a substance from a liquid to a gas at a constant temperature
How do gases exert pressure
Gas particles are constantly moving at a high speed in random directions, and collide repeatedly with each other and the surface inside a container
Each impact on the surface exerts a tiny force, the total force causes a pressure on the surface
Pressure formula
Pressure = force / area
Lowest possible temparature
- 274 degrees, or 0 kelvin
How to convert from degrees to kelvin
Degrees ——> kelvin = +273
Kelvin ——> degrees = -273
Effects of temperature on pressure of a gas at a constant value
> As the temperature increases gas particles in gain energy and as a result, it’s velocity increases
velocity increases there are more frequent collisions with the wall of the container
as the velocity increases, the aortic,es are able to hit the container at a higher speed
pressure is able to force divided by area the greater force per second result in increase of pressure
pressure is directly proportional to the temperature in kelvin
How to find temperature or pressure increase or decrease
T2 x P1 = T1 x P2
