elements compounds mixtures

Question 1

Definition of an element

Answer 1

Element is a substance that consists of only one type of atom
And can not be split into anything simpler by chemical means

Question 2

Definition of a compound

Answer 2

Substances of where two or more diff elements are chemically combined

Question 3

What is a molecule

Answer 3

A substance made of two or more atoms chemically combined

Question 4

What is a pure substance

Answer 4

A substance that contains only one type of element of compound

Question 5

How do you distinguish between the purity of a substance in terms of melting and boiling points

Answer 5

Pure substances melt and boil at specific temperatures

If it has a range of melting points it is impure

Question 6

If you have a gradual decrease in temperature during change of state, what does that suggest about the purity of a substance and why

Answer 6

It is impure because it’s melting and boiling points have a range

Question 7

Explain why compounds are always pure

Answer 7

Although they have more than one type of atom, the ratio is always in fixed compositions

Question 8

Give an example of elements that explains how elements have different properties in mixtures and compounds

Answer 8

Mixture of hydrogen and water is a gas the explodes

Compound of hydrogen and water is water

Question 9

What will adding salt to water do to the melting and boiling point of water and why

Answer 9

The melting point will decrease and the boiling point will increase due to the presence of impurities

Question 10

What is the residue and what is the filtrate

Answer 10

The residue is what’s left on the filter paper

The filtrate is what seeps through

Question 11

What two types of mixtures can you separate while using filtration

Answer 11

Insoluble solid from a liquid

Liquid from an insoluble solid

Question 12

What method of separation can you use to separate a solute from a solution

Answer 12

Crystallization

Question 13

When heating an evaporating basin in crystallization, what are we waiting for and how do we test it

Answer 13

Waiting till there is a saturated solution of crystals,

Test it using a glass rod

Question 14

Give a reason why simple distillation may be better to use than crystallization when trying to separate a solution

Answer 14

The water is also able to be collected rather than evaporating

Question 15

Why is it best to provide the water going in from the bottom in distillation

Answer 15

the pressure allows the jacket to always be full

Question 16

What is a better alternative to a Bunsen burner and why

Answer 16

Heating mantle because you can control temperature

Question 17

What is a miscible liquid

Answer 17

Liquids that mix together

Question 18

What does a condenser contain and what does it condense

Answer 18

Condenser contains circulating cold water

Condenses vapor

Question 19

In fractional distillation, which liquid condenses first

Answer 19

The liquid with a lower boiling point

Question 20

What is the solvent front

Answer 20

The highest level of the solvent on the paper

Question 21

If the dye does not move up from the solvent line, what does that say about its solubility and the solvent that you’ve used

Answer 21

The dye is not soluble in the solvent used

- you need to use a different solvent

Question 22

What does it mean if a substance has high affinity for paper

Answer 22

It sticks well to the paper

Question 23

When talking about results of a chromatogram, why do you describe the number of dyes as “minimum” (of say three)

Answer 23

Because there could be more dyes which perhaps travelled the same distance and have the same color

Question 24

Why do substances in a mixture each move up at different rates in chromatography and why

Answer 24

Because they have different attractions the the mobile and stationary phase
- due to their properties

Question 25

If you use different paper and solvent will the Rf values be the same or different

Answer 25

Different

Question 26

If the Rf value is closer to 1, what does that imply about the solubility

Answer 26

It is very soluble in the solvent

Question 27

If an impurity is added to a substance, the melting point will… and the boiling point will…..

Answer 27

Decrease
Increase