Chemistry: Chapter 3 (Atoms Combining)

Question 1

Definition of Element

Answer 1

A substance that contains only one kind of atom and cannot be broken down further into another substance.

Question 2

Definition of Compounds

Answer 2

A substance that is made of atoms of different elements that are chemically bonded together.

Question 3

Definition of Mixture

Answer 3

Different substances that are physically mixed together.

Question 4

What are the 3 signs of chemical change?

Answer 4

• one or more new chemical substances are formed
• energy is taken in or given out during the reaction
• the change is usually difficult to reverse

Question 5

What are 2 ways to reverse a chemical change?

Answer 5

Heating with carbon and electrolysis

Question 6

How to differenciate physical changes from chemical changes?

Answer 6

If it produces a new substance, it is chemical change. If it does not, it is physical change.

Question 7

3 signs of chemical reactions

Answer 7

• colour change
• sweet smell / foul stench
• temperature change

Question 8

Why do atoms form bonds?

Answer 8

Atms form bonds together in order to obtain a full valence electron shell.

Question 9

Which group of gases are unreactive?

Answer 9

Group VIII, the noble gases

Question 10

Why does sodium gain a single positive charge?

Answer 10

When the sodium atom donates an electron, the number of protons is one more than electrons.

Question 11

What are positive and negative ions called?

Answer 11

Cation (+) and Anion (-)

Question 12

Why do atoms of Group VIII not form ions?

Answer 12

They have a full electron shell and do not need to receive or donate electrons, they are unreactive.

Question 13

Definition of Ionic Bond

Answer 13

A strong electrostatic attraction between ions of opposite charge.

Question 14

Definition of Lattice

Answer 14

3D structure of regular and repeating pattern of oppositely charged ions.

Question 15

What is the overall charge of the compound NaCl?

Answer 15

No overall charge, the charges on the ions cancel each other out.

Question 16

Which element goes at the front of a compound name?

Answer 16

The element with a positive charge

Question 17

Definition of Molecules

Answer 17

Two or more atoms held together by covalent bonds.

Question 18

Why do carbon atoms not form ions?

Answer 18

Carbon and other elements in Group IV would have to lose or gain many electrons, which would take too much energy, thus carbon only shares electrons.

Question 19

Why do non-metal elements not form ionic bonds with each other?

Answer 19

Non-metals only receive electrons to form anions, anions will repel each other so it cannot form ionic bonding.

Question 20

Definition of Covalent Bond

Answer 20

Atoms gaining full electron shells by sharing electrons with each other.

Question 21

Definition of Regular Lattice

Answer 21

Regular lattice grows in all directions, giving a crystal-like structure.

Question 22

What is the weak force in between molecultes called?

Answer 22

Intermolecular force

Question 23

Properties of Ionic Compounds

Answer 23

• high MP and BP
• usually soluble in water
• can conduct electricity when dissolved or molten (ions are not free to move in solid state)

Question 24

Properties of Covalent Compounds

Answer 24

• low MP and BP
• usually insoluble in water
• cannot conduct electricity (no charge bc no ions)

Question 25

What are the two types of covalent structures?

Answer 25

Simple molecular structure and giant covalent structure

Question 26

What are the three giant covalent structures?

Answer 26

Graphite, diamond and silica

Question 27

Properties of Diamond and Silica

Answer 27

• very hard (held in place by 4 strong covalent bonds)
• high melting point
• cannot conduct electricity (no moving electrons)

Question 28

Properties of Graphite

Answer 28

• soft and slippery (layers can slide over each other)
• good conductor of electricity (delocalised electrons moving between layers)

Question 29

Uses of Graphite

Answer 29

• lubricant in engines
• electrodes in electrolysis

Question 30

Use of Diamond

Answer 30

• tools for drilling and cutting

Question 31

Uses of Silica

Answer 31

• in bricks for lining furnaces
• sandpaper

Question 32

Definition of Allotropes

Answer 32

Different forms of an element

Question 33

Definition of Metallic Bond

Answer 33

The electrostatic attraction between the positive ions in a ‘sea’ of delocalised electron that move freely.

Question 34

What force are metal ions held together by?

Answer 34

Electrostatic attraction

Question 35

Properties of Metals

Answer 35

• high melting point (high heat to overcome strong electrostatic forces between metal ions and delocalised electrons)
• malleable and ductile (layers of metal ions can slide over each other)
• good conductors of heat (free electrons take in heat energy, which makes them move faster)
• good conductors of electricity( free electrons move through the lattice as a current of electricity, when a voltage is applied across the metal.

Question 36

Which metal is the best conductor?

Answer 36

Silver (copper is next but is used more often as it is cheaper)

Question 37

Which bonds use electrostatic attraction?

Answer 37

Ionic bonding and Metallic bonding

ionic: cation & anion
metallic: positive metal ions & sea of delocalised electrons

Question 38

What does it mean to be malleable and ductile?

Answer 38

Malleable: can be bent and pressed into shape
Ductile: can be drawn into wires