C1-History Of The Atom and Separating Mixtures

Question 1

What did early ancient greeks believe about the atom

Answer 1

Early ancient greeks believed that the atom was a tiny sphere that could not be divided

Question 2

What was discovered in 1897

Answer 2

In 1897 JJ Thompson concluded from experiments the presence of an electron. An electron is a tiny negative particle within an atom.

This disproved the theory that the atom was a solid sphere and showed that it contained internal structures

Question 3

What model was concluded from this

Answer 3

The plum pudding model was developed from this

The plum pudding model showed the atom as a positively charged ball with negatively charged electrons within it

Question 4

What was the gold foil experiment

Answer 4

The gold foil experiment was an experiment conducted by ernest Rutherford in 1909

In the experiment the scientists fired positively charged alpha particles at the gold foil. If the plum pudding model was true then all of the alpha particles should have gone straight through .

Question 5

What happened in the scattering experiment and what did this show

Answer 5

Most of the particles passed through the gold foil which showed the atoms where mainly made up of empty space

Some of the particles deflected(changed direction) which showed that the centre of the atom must have a positive charge which caused the particles to change direction

Some of the particles also bounced back which showed that the atom had a great deal of mass in the centre that we now call an nucleus

Question 6

What model was developed as a result of the scattering experiment

Answer 6

The nuclear model (positive nucleus , empty space , electrons)was developed as a result of the alpha scattering experiment which was later altered by Niels Bohr to include that electrons orbited the nucleus in shells at fixed distances away.

Question 7

What other discoveries were made to alter the nuclear model

Answer 7

• The discovery of protons altered the nuclear model. They were discovered as tiny positively charged particles that gave the nucleus its positive charge
• About 20 years after the acceptance of the nuclear model James Chadwick came up with the idea that nuclei also contain neutrons particles called neutrons

Question 8

What are the measurements in an atom and what is there overall charge

Answer 8

The overall charge of an atom is zero because it has the same amount of protons and electrons

• Radius of an atom 0.1 nanometer (1x10-10 meters)
• Nucleus of an atom 1x10-14m

Question 9

What are the relative charges and realtive masses of protons neutrons and electrons

Answer 9

Relative masses 
Protons-1
Neutrons-1
Electrons-very small
Overall charges 
Protons-+1
Neutrons~0
Electrons~-1

Question 10

What are isotopes

Answer 10

Different forms of the same atoms with different numbers of neutrons and the same numbers of protons

Question 11

What type of process is chromatography

Answer 11

Chromatography is a physical process . It does not involve a chemical reaction and no new substances are made

Question 12

What does paper chromatography allow us to do

Answer 12

Paper chromatography allows us to seperate substances based on their solubility

Question 13

What is a solvent

Answer 13

A solvent is a liquid that will dissolve other substances

Question 14

What is the stationary phase in chromatography ? What is the mobile phase in Chromatography?

Answer 14

• The stationary phase in chromatography is the paper as it does not move
• The solvent is the mobile phase as it moves

Question 15

How does paper chromatography work

Answer 15

• Paper chromatography works because each chemical in a mixture is attracted to the stationary phase (the paper) to a different extent. This means they form spots at different points
• Chemicals that are strongly attracted to the paper wont move up very far
• Chemicals that have a weaker attraction to the paper will move further up the paper

Question 16

How can you tell if a substance is pure or impure using paper chromatography

Answer 16

• Pure substances will produce a single spot in all solvents
• Chemicals in a mixture will seperate into different spots on the chromatagram

Question 17

Why do you have to draw on the chromatogram paper only in pencil

Answer 17

-You have to draw in pencil on the chromatogram because if you drew in pen the pen ink would move up the paper with the solvent

Question 18

How do you conduct a chromatography practical ink (not required one just general)

Answer 18

• take a special piece of chromatography paper
• Then draw a pencil line at the bottom of the paper
• Put two dots of ink on the pencil line at the bottom
• Place the bottom of the chromatography paper in the solvent
• The solvent will now make its way up the paper. It has dissolved the ink in the coloured dot. Where the dot will form depends on its attraction to the stationary phase

Question 19

What can simple distillation be used to do

Answer 19

Simple distillation can be used to separate a liquid from a solid if we want to keep the liquid

Question 20

What are the two main steps in simple distillation

Answer 20

1. First evaporate the liquid by heating

2) Then condense the vapour by cooling

Question 21

Why does cold water continually run through the condensor

Answer 21

Cold water continually runs through the condensor to keep the condensor cool

Question 22

What are the in depth steps in fractional distillation

Answer 22

1) Heat the solution using a bunsen burner
2) as you heat the liquid it will begin to evaporate and rise up the glass tube
3) The vapour will then pass through the condensor and will condense as it does so . Turning back into a liquid
4) The liquid will be collected at the end and the solid will be left in the conical flask

Question 23

How can physical seperation techniques be used

Answer 23

Physical seperation techniques can be used to seperate mixtures only

-They cannot be used to separate elements in compounds

Question 24

What is filtration used to do

Answer 24

Filtration is used to seperate an insoluble solid from a liquid

Question 25

How can you conduct a filtration

Answer 25

• To conduct filtration you need a filter funnel and filter paper
• First pour the liquid with an insoluble solid through the filter paper and funnel
• The liquid will be able to pass through the tiny pores in the filter paper
• The solid will not be able to pass through and will be trapped
• The liquid and solid will be seperated

Question 26

What can crystalisation be used to do

Answer 26

-Crystalisation can be used to separate a soluble solid(one that dissolves) from a liquid

Question 27

What are the steps in crystalisation

Answer 27

• To conduct a cystalisation leave the solution of soluble solid and liquid for a few days until all the liquid has evaporated
• Once the liquid has evaporated you will be left with solid crystals from the solid
• (to make crystalisation happen faster gently heat the solution so the water evaporates more quickly)