Elements, Compounds and Mixtures

Question 1

What is an element?

Answer 1

a substance that consists of only one type of atom and it cannot be broken down into anything simpler by chemical means

Question 2

What is a compound?

Answer 2

2 or more different elements chemically bonded together

Question 3

What is a mixture?

Answer 3

a group of elements that can be separated and aren’t chemically bonded together

Question 4

Describe the melting point/boiling point of pure substances

Answer 4

fixed melting/boiling point

Question 5

Describe the melting/boiling point of mixtures

Answer 5

can melt/boil at different temperatures as its not solely one pure element

Question 6

What is simple distillation?

Answer 6

separating a liquid from a solution

1. boil the mixture
2. water vapour of the liquid with the lower boiling point condenses back into a liquid when passed through a condenser
3. pure substance is left behind the flask

commonly used to purify water or separate alcohol from water

Question 7

What is fractional distillation?

Answer 7

separating a mixture of different liquids with different boiling points

1. boil the mixture until it reaches the lowest boiling point of one of the liquids
2. that water vapour condenses back into a liquid
3. repeat for all boiling points from the lowest to highest

commonly used for separating crude oil

Question 8

What is filtration?

Answer 8

separating an insoluble solid from a liquid

1. pour the mixture into filter paper
2. filtrate (liquid) passes through and is collected in the conical flask
3. insoluble solid is left in the filter paper

Question 9

What is crystallisation?

Answer 9

obtaining a salt containing water of crystalisation from a salt solution

1. heat solution in crucible to evaporate water until crystals form
2. leave to cool and filter to get rid of excess liquid
3. pat dry with towel and leave in a warm place to evaporate any excess liquid