Introduction To Chemistry (including Seperating Techniques)

Question 1

What is a mixture?

Answer 1

Two or more different atoms not chemically bonded together

Question 2

How can we separate a mixture?

Answer 2

By physical means such as:
Changing the temperature
Dissolving part of the mixture into a solvent such as water

Question 3

How can we determine weather a substance is pure?

Answer 3

Pure substances have sharp melting and boiling points

Question 4

What method do we use to separate a solid from a liquid?

Answer 4

Filtration - leaves us with residue and filtrate

Question 5

What method do we use to separate a solute from a solution?

Answer 5

Crystallisation

Question 6

What method do we use to separate the components of a solution?

Answer 6

Simple distillation - water boils and is condensed back to a liquid by the condenser, the salt remains in the flask

Question 7

What method do we use to separate a mixture of liquids?

Answer 7

Fractional distillation - takes advantage of the different boiling points

Question 8

What method do we use to separate a variety of mixtures?

Answer 8

Paper chromatography

Question 9

What observations should we make when describing substances?

Answer 9

.state (solid liquid or gas)
.coloured/colourless
.crystalline/powdered (solids)
.clear/cloudy (liquids)

Question 10

What observations should we make when describing changes?

Answer 10

.any effervescence?
.has a solid appeared or disappeared?
.colour change?
.any unusual sounds or smells?

Question 11

Characteristics of a physical change?

Answer 11

.no new substances created
.are usually easy to reverse
.absorb or release small amounts of energy

Question 12

Characteristics of a chemical change?

Answer 12

.create new substances
.are usually difficult to reverse
.absorb or release large amounts of energy

Question 13

Describe a chemical test for water

Answer 13

Anhydrous copper sulphate turns from white to blue
.tells you that water is present but jot how pure it is

Question 14

Describe two physical tests for water

Answer 14

Melting point - 0C
Boiling point - 100C
Purer water matches these properties more closely

Question 15

What is an element

Answer 15

A substance containing only one type of atom

Question 16

Metallic properties

Answer 16

High MP/BP
Electrical conductors
Malleable
Shiny

Question 17

Non metal properties

Answer 17

Low MP/BP
Electrical insulators
Brittle
Dull

Question 18

What is a compound?

Answer 18

A substance containing more than one type of atom chemically bonded together

Question 19

How can we make compounds?

Answer 19

Heating elements together

Question 20

Give an example of two elements that hen form a compound have completely different properties

Answer 20

Sodium (corrosive metal) + chlorine (toxic gas) —> sodium chloride (salt)

Question 21

What are the three types of compounds?

Answer 21

Metallic, ionic and covalent

Question 22

How do you make a metallic compound?

Answer 22

Two metals

Question 23

How do you make an ionic compound?

Answer 23

Metal and non metal

Question 24

How do you make a covalent compound?

Answer 24

Two non metals

Question 25

What is a solute?

Answer 25

The substance which is going to be dissolved

Question 26

What is a solvent?

Answer 26

The substance which is going to do the dissolving

Question 27

What is a solution?

Answer 27

The resulting mixture of a solute dissolved in solvent

Question 28

What does saturated mean?

Answer 28

A solution which no more solute can be dissolved

Question 29

What is a suspension?

Answer 29

A solid floating in a liquid because it cannot be dissolved

Question 30

What does soluble mean?

Answer 30

A substance which can be dissolved

Question 31

What does insoluble mean?

Answer 31

A substance which cannot be dissolved

Question 32

How do we measure solubility?

Answer 32

In g per 100g of solvent