5 — elements, compounds and mixtures

Question 1

Element

Answer 1

An element is a pure substance that cannot be broken down into simpler substances by chemical processes or electricity.

Question 2

Metalloids

Answer 2

Elements that have properties of both metals and non-metals

Question 3

Compound

Answer 3

A compound is a pure substance containing 2 or more different elements that r chemically combined in a fixed ratio

Question 4

Separation of chemical compounds into constituent elements

Answer 4

1. Thermal decomposition
2. Electrolysis

Question 5

Molecule

Answer 5

A molecule is a group of 2 or more non-metal atoms that r chemically combined tgt

(Can be atoms of same or different elements)
2 atoms chemically combined: diatomic molecules
3 or more atoms chemically combined: polyatomic molecules

Question 6

Mixture

Answer 6

A mixture is made up of 2 or more elements and/or compounds that r not chemically combined

Question 7

Explain if x is a compound or a mixture

Answer 7

It is a mixture since x is made up of y number of compounds and are not chemically combined tgt.

Question 8

Composition of elements, compounds and mixtures (avoid using definitions to compare)

Answer 8

Formation:
E: mostly natural occurring
C: from a chemical reaction
M:usually from physical mixing

Composition
E: -
C: fixed ratio
M: no fixed ratio or in any proportion

Properties
E: -
C: diff properties from its constituent elements
M: same properties as its constituent substances

Melting and boiling points
E: fixed
C: fixed
M:melt and boil over a range of temperatures

Energy
E: -
C: a chem reaction takes place when a compound is formed — usually has an energy change
M: no chem reaction takes place when a mixture is formed — usually no or little energy change

Separation:
E: -
C: chemical reactions or by electricity
M: physical methods