Changes Of State

Question 1

What was daltons model

Answer 1

• small indestructible spheres
• atoms in one element are all the same
• atoms in one type of element are different from atoms in another element

Question 2

What was Thomson’s model

Answer 2

• 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

Question 3

What was Rutherfords model

Answer 3

• 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

Question 4

What was Bohrs model of the atom

Answer 4

• suggested that electrons could only move in fixed orbits called electron shells
• without them, the electrons would spiral until they hit the nucleus

Question 5

How big are atoms and molecules

Answer 5

10^-10
Or
1 x 10^-10

Question 6

Density defenition

Answer 6

Density is a measurement of the amount of a mass of a substance contained in a given volume

Question 7

What is the formula for density?

Answer 7

Density = Mass / volume

Question 8

How do you find the density of an irregularly shaped object?

Answer 8

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

Question 9

What is the difference between heat and temperature

Answer 9

• 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

Question 10

What units of measure do you use to measure temperature

Answer 10

• kelvin
• degrees Celsius

Question 11

To measure heat, you use

Answer 11

• joules

Question 12

What is the definition of specific heat capacity

Answer 12

Specific heat capacity is the amount of energy needed to raise the temperature of 1Kg of a substance by 1 degree

Question 13

specific heat capacity equation

Answer 13

Energy = Mass x Specific Heat Capacity x (change in) Temperature

Question 14

What are the units for specific heat capacity

Answer 14

J/Kg degrees Celsius

Question 15

What is internal energy

Answer 15

The sum of randomly distributed kinetic and potential energy of all of the particles within an object

Question 16

Each state and how much kinetic energy they have

Answer 16

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

Question 17

What is specific latent heat

Answer 17

The amount of heat needed to change the state of 1Kg of a substance at a constant temperature

Question 18

How to calculate the energy required for the specific latent heat

Answer 18

Energy required = mass (kg) x specific latent heat of fusion

Question 19

Specific latent heat of fusion

Answer 19

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

Question 20

Specific latent of vaporisation

Answer 20

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

Question 21

How do gases exert pressure

Answer 21

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

Question 22

Pressure formula

Answer 22

Pressure = force / area

Question 23

Lowest possible temparature

Answer 23

• 274 degrees, or 0 kelvin

Question 24

How to convert from degrees to kelvin

Answer 24

Degrees ——> kelvin = +273
Kelvin ——> degrees = -273

Question 25

Effects of temperature on pressure of a gas at a constant value

Answer 25

> 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

Question 26

How to find temperature or pressure increase or decrease

Answer 26

T2 x P1 = T1 x P2