Atomic structure, ions, equations

Question 1

What is an atom?

Answer 1

The smallest unit of an element.

Question 2

What are the three subatomic particles and their properties?

Answer 2

Proton: +1 charge, mass 1; Neutron: 0 charge, mass 1; Electron: -1 charge, negligible mass.

Question 3

What does the atomic number (Z) represent?

Answer 3

The number of protons in an atom.

Question 4

What does the mass number (A) represent?

Answer 4

The total number of protons and neutrons in an atom.

Question 5

What is an isotope?

Answer 5

Atoms of the same element with the same number of protons but different numbers of neutrons.

Question 6

What is the electron configuration of sodium (Na)?

Answer 6

2,8,1

Question 7

What is a cation?

Answer 7

A positively charged ion formed by losing electrons.

Question 8

What is an anion?

Answer 8

A negatively charged ion formed by gaining electrons.

Question 9

What is ionic bonding?

Answer 9

Electrostatic attraction between oppositely charged ions.

Question 10

Give an example of ionic bonding using sodium and chlorine.

Answer 10

Na → Na⁺ + e⁻ ; Cl + e⁻ → Cl⁻ ; Na⁺ + Cl⁻ → NaCl

Question 11

Why must chemical equations be balanced?

Answer 11

To obey the law of conservation of mass.

Question 12

Give a balanced chemical equation for the formation of water.

Answer 12

2H₂ + O₂ → 2H₂O

Question 13

What is filtration used for?

Answer 13

Separating insoluble solids from liquids.

Question 14

What is crystallisation used for?

Answer 14

Obtaining pure salt crystals from a solution.

Question 15

What does distillation do?

Answer 15

Separates liquids based on their boiling points.

Question 16

What does chromatography separate?

Answer 16

Substances based on their solubility.

Question 17

What is the formula for Rf value?

Answer 17

Rf = Distance moved by substance / Distance moved by solvent

Question 18

How did Mendeleev arrange the periodic table?

Answer 18

By atomic mass and left gaps for undiscovered elements.

Question 19

How is the modern periodic table arranged?

Answer 19

By atomic number.

Question 20

What do Group 1 elements have in common?

Answer 20

1 outer electron; reactivity increases down the group.

Question 21

Give the reaction of sodium with water.

Answer 21

2Na + 2H₂O → 2NaOH + H₂

Question 22

What do Group 7 elements have in common?

Answer 22

7 outer electrons; reactivity decreases down the group.

Question 23

Give an example of a halogen displacement reaction.

Answer 23

Cl₂ + 2KBr → 2KCl + Br₂

Question 24

What are the properties of Group 0 (noble gases)?

Answer 24

Full outer shell, inert, unreactive, boiling points increase down the group.

Question 25

What is the formula for rate of reaction?

Answer 25

Rate = Quantity of reactant used or product formed / Time taken

Question 26

What theory explains how particles react?

Answer 26

Collision theory.

Question 27

What is activation energy?

Answer 27

The minimum energy required for particles to react.

Question 28

How does temperature affect reaction rate?

Answer 28

Increases particle energy → more successful collisions → faster rate.

Question 29

How does concentration affect rate?

Answer 29

More particles in the same volume → more collisions → faster rate.

Question 30

How does surface area affect rate?

Answer 30

Larger surface area → more collisions → faster rate.

Question 31

How do catalysts affect rate?

Answer 31

Lower the activation energy required.

Question 32

What is the difference between exothermic and endothermic reactions?

Answer 32

Exothermic releases energy; endothermic absorbs energy.

Question 33

Describe one experiment for Required Practical 5.

Answer 33

React magnesium with HCl and measure hydrogen gas produced over time.

Question 34

Describe a second experiment for Required Practical 5.

Answer 34

React sodium thiosulfate with HCl and time how long a cross disappears.

Question 35

What is crude oil?

Answer 35

A mixture of hydrocarbons formed from ancient biomass.

Question 36

What is the general formula for alkanes?

Answer 36

CₙH₂ₙ₊₂

Question 37

What is fractional distillation?

Answer 37

Separates hydrocarbons based on boiling points.

Question 38

What are the properties of short-chain hydrocarbons?

Answer 38

Low boiling point, more flammable.

Question 39

What are the properties of long-chain hydrocarbons?

Answer 39

High boiling point, less flammable.

Question 40

What is complete combustion?

Answer 40

Hydrocarbon + O₂ → CO₂ + H₂O

Question 41

What is incomplete combustion?

Answer 41

Hydrocarbon + O₂ → CO + H₂O (or C + H₂O)

Question 42

What is cracking?

Answer 42

Breaking long-chain alkanes into shorter alkanes and alkenes.

Question 43

What are two types of cracking?

Answer 43

Thermal cracking (high temp and pressure) and catalytic cracking (uses a catalyst).

Question 44

What are alkenes?

Answer 44

Unsaturated hydrocarbons with at least one C=C bond.

Question 45

What is the general formula of alkenes?

Answer 45

CₙH₂ₙ

Question 46

What is hydrogenation of alkenes?

Answer 46

Alkene + H₂ → Alkane (with Ni catalyst)

Question 47

What is halogenation of alkenes?

Answer 47

Alkene + Halogen → Dihaloalkane

Question 48

How can bromine water test for alkenes?

Answer 48

Turns from orange to colourless in presence of a C=C bond.

Question 49

What is hydration of alkenes?

Answer 49

Alkene + H₂O (steam) → Alcohol (with acid catalyst)

Question 50

What is addition polymerisation?

Answer 50

Monomers with C=C bonds join to form polymers; only one product formed.

Question 51

What is an example of addition polymerisation?

Answer 51

Ethene → Poly(ethene)

Question 52

How are polymers represented in drawings?

Answer 52

Repeating units inside brackets with an 'n' to show many units.