chap 5.1

Question 1

what is an element?

Answer 1

an element is a pure substance that cannot be broken down into two or more simpler substances by chemical methods

Question 2

what groups can elements be classified into?

Answer 2

• metals
• non-metals
• metalloids (have properties of both metals and non-metals)

Question 3

what can elements appear as?

Answer 3

1. atoms - if they are not chemically bonded to each other
2. molecules - if they are covalently bonded
3. a lattice of ions with a “sea of delocalised electrons”

Question 4

what are compounds?

Answer 4

a compound is a pure substance containing two or more different elements that are chemically combined in a fixed ratio

Question 5

how can compounds be separated into its constituent elements?

Answer 5

1. thermal decomposition - breaking down compound by exposing it to strong heat
2. electrolysis - breaking down compounds by passing electric current through it

Question 6

what is a molecule?

Answer 6

a molecule is a group of two or more non-metal atoms that are chemically combined together

Question 7

what are the two types of molecules?

Answer 7

1. diatomic molecules - two atoms chemically combined
2. polyatomic molecules - three or more atoms chemically combined

Question 8

what is a mixture?

Answer 8

a mixture is made up of two or more elements and/or compounds that are not chemically combined

Question 9

what is the difference between compounds and mixtures?

Answer 9

a compound has a fixed proportion of the different kinds of atoms it is made up of. in contrast, mixtures do not have substances in fixed ratios