C1: Atomic Structure & the Periodic Table

Question 1

what is an atom?

Answer 1

An atom is the smallest part of an element that can exist

Question 2

What is an element?

Answer 2

An element is a substance of only one type of atom

Question 3

How are the elements listed and approximately how many are there?

Answer 3

They are listed in the periodic table; there are approximately 100

Question 4

Elements can be classified into two groups based on their properties; what are these groups?

Answer 4

Metals and non-metals

Question 5

What is a compound?

Answer 5

Two or more elements combined chemically in fixed proportions which can be represented by formulae

Question 6

Do compounds have the same properties as their constituent elements?

Answer 6

No, they have different properties

Question 7

What is a mixture?

Answer 7

A mixture consists of two or more elements or compounds not chemically combined together

Question 8

Does mixtures have the same chemical properties as its constituent materials?

Answer 8

No, it does not have the same chemical properties

Question 9

What are the methods through which mixtures can be separated? Do these involve chemical reactions?

Answer 9

• Filtration
• Crystallisation
• Simple Distillation
• Fractional Distillation
• Chromatography
  They do not involve chemical reactions

Question 10

Describe and explain filtration

Answer 10

Filtration is used to separate an insoluble solid from a liquid.
APPARATUS: Filter paper + Funnel
1. start by pouring our mixture into the filter paper
2. the liquid ( water) passes through the tiny pores in the filter paper
The solid material, cannot pass through the filter paper so its trapped.
at the end we have our liquid separated from our solid.

Question 11

Describe and explain evaporation

Answer 11

Evaporation is a technique for separation of a solid dissolved in a solvent from a solvent
STEPS:
1. Pour the solution into an evaporating dish
2. Slowly heat the solution. The solvent will evaporate and the solution will get more concentrated. Eventually, crystals will start to form
3. Keep heating the evaporating dish until all you have left are dry crystals

Question 12

Describe and explain Crystallisation

Answer 12

Crystallisation is used to separate a soluble solid from a liquid
STEPS:
1. Pour the solution into an evaporating dish and gently heat the solution
2. once some of the solvent has evaporated, or when you see crystals start to form, remove the dish from the heat and leave the solution to cool
3. the salt should start to form crystals as it becomes insoluble in the cold, highly concentrated solution
4. filter the crystals out of the solution, and leave them in a warm place to dry.

Question 13

Describe and explain simple distillation

Answer 13

Simple distillation is used for separating out a liquid from a solution

STEPS:
1. the solution is heated. the part of the solution that has the lowest boiling point evaporates first
2. the vapour is then cooled, condenses (turns back into a liquid) and is then collected
3. the rest of the solution is left behind in the flask

Question 14

Problems with simple distillation

Answer 14

• you can only use it to separate things with very different boiling points- if the temperature goes higher than the boiling point of the substance with the higher boiling point, they will mix again
• If you have a mixture of liquids with similar boiling points you need another method to separate them- like fractional distillation

Question 15

Describe and explain fractional distillation

Answer 15

Fractional Distillation is used if you’ve got a mixture of liquids that would like to be separated.
STEPS:
1. Put your mixture in a flask and stick a fractionating column on top. Then you heat it.
2. The different liquids will all have different boiling points- so they will evaporate at different temperatures
3. The liquid with the lowest boiling point evaporates first. When the temperature on the thermometer matches the boiling point of this liquid, it will reach the top of the column
4. Liquids with higher boiling points might also start to evaporate. But the column is cooler towards the top. So they will only get part of the way up before condensing and running back down towards the flask
5. When the first liquid has been collected, your raise the temperature until the next one reaches the top

Question 16

Describe and explain Paper Chromatography

Answer 16

Chromatography is used to separate a mixture of substances dissolved in a solvent. This technique can be used to separate different dyes in an ink

STEPS:
1. Draw a line near the bottom of a sheet of filter paper
(Use a pencil to do this- pencil marks are insoluble and won’t dissolve in the solvent)
2. Add a spot of the ink to the line and place the sheet in a beaker of solvent
3. Make sure the ink isn’t touching the solvent because you don’t want it to dissolve into it
4. place a lid on top of the container to stop the solvent evaporating
5. the solvent seeps up the paper, carrying the ink with it.
6. Each different dye in the ink will move up the paper at a different rate so the dyes will separate out. Each dye will form a spot in a different place
7. If ant of the dyes in the ink are insoluble (won’t dissolve) in the solvent you’ve used, they’ll stay on the baseline
8.When the solvent has nearly reached the top of the paper, take the paper out of the beaker and leave it to dry
9. the end results in a pattern of spots called a chromatogram