CHEMISTRY

Question 1

What is an oxidation reaction?

Answer 1

When a substance gains oxygen OR When a substance loses electrons

Question 2

What is a reduction reaction?

OIL RIG

Answer 2

When a substance loses oxygen OR when a substance gains electrons

Question 3

When metals react with oxygen they always form…

Answer 3

metal oxides!

Question 4

What is the reactivity series and which four metals come on top?

Answer 4

It explains how reactive metals are - some metals lose electrons quicker than others.

K-Na-Ca-Mg

Question 5

Describe a replacement reaction

Answer 5

When a more reactive element displaces a less reactive element from a solution of its salt

Question 6

where is the nucleus?

Answer 6

in the middle of the atom

Question 7

what does the nucleus contain?

Answer 7

protons and neutrons

Question 8

what are protons mass and charge?

Answer 8

positive charge / relative mass of 1

Question 9

what are neutrons mass and charge?

Answer 9

no charge/realtive mass of 1

Question 10

what are electrons mass and charge?

Answer 10

negative charge/ relative mass of 0

Question 11

where do the electrons belong?

Answer 11

move along the outside of the nucleus in electron shells.

Question 12

what appears at the top of the element symbol?

Answer 12

mass number

Question 13

what appears at the bottom of the element symbol?

Answer 13

atomic number

Question 14

what is an element?

Answer 14

a substance made up of Atoms that have the same number of protons in their nucleus

Question 15

what decides an atom’s type?

Answer 15

the number of protons in the nucleus

Question 16

what are isotopes?

Answer 16

different forms of the same element

Question 17

what do isotopes include ?

Answer 17

the same atomic number but different mass numbers

Question 18

what is a compound?

Answer 18

when elements react atoms combine to form compounds

Question 19

how many substances are in a compound?

Answer 19

two or more elements

Question 20

name the three main states of matter and the fourth for a bonus!

Answer 20

solid liquid gas plasma (as in the Sun - when atoms meld into each other)

Question 21

What do the state symbols mean? (s) (l) (g) (aq)

Answer 21

(s) = solid (l) = liquid (g) = gas (aq) = aqueous = disolved in water

Question 22

Describe the particle theory of matter

Answer 22

The particle theory of matter explains matter as being made up of tiny particles and how they are arranged and move. In solids, particles have a regular arrangement, they’re very close together and vibrate around fixed positions. In liquids, particles have a random arrangement, they’re close together but they flow around each other. In gases, they are arranged randomly, they’re further apart and move quickly in all directions.

Question 23

HT: What problems are there with the particle theory of matter?

Answer 23

The particle theory does not take into account 1) forces acting between particles 2) the volume of the particles, even though they’re very small 3) the space between particles AND EXTRA IDEA: 4) insights from quantum physics - e.g. action at a distance (paired electrons can change spin at the same time even at great distances)

Question 24

What is graphene?

Answer 24

A single layer of carbon Atoms are arranged in hexagonal structures just one atom thick It is very strong, has good thermal properties, is an electrical conductor and is nearly transparent.

Question 25

What are fullerenes?

Answer 25

Carbon that comes in the form of hollow shapes such as balls, tubes and cages. The Buckminsterfullerenes or buckyballs (named after American inventor and thinker, Buckminster Fuller) has the shape of a football - C(60) - tessellated with hexagonal and pentagonal shapes. Because they are very small and stable Fullerenes are used to deliver drugs into the body, as lubricants, as catalysts, and reinforcing materials (e.g., frames of tennis rackets) Buckyballs also turn darker when intense light is shone at them - good for safety glasses. For MORE on this see docbrown’s pages: http://www.docbrown.info/page03/nanochem04.htm

Question 26

What are polymers? (3 pts)

Answer 26

1. Very large organic molecules (organic = based on carbon)
2. The constituent atoms are held together by strong covalent bonds Intermolecular forces between the molecular strands are also very strong.
3. Solid at room temperature.

Extra info:

Plastics are all polymers - bags, plastic bottles.

E.g., Polythene is produced when lots of ethene molecules are joined together in an “addition polymerisation” reaction.

DOWNSIDE: can fill up landfills, don’t biodegrade easily, can cause a mess in our seas and oceans!

Question 27

Describe metallic bonding

Answer 27

A metallic bond is the attraction between the positive ions and delocalised negatively charged electrons. Recall that electrons in metals flow freely around their atoms, because metals have a giant structure in which the electrons in the outer shell I’m not bound to anyone atom..

Question 28

Name some properties of metals

Answer 28

Metallic bonds are very strong. They have high melting and boiling points. This means they are useful for building and structure materials. They can conduct electricity they have good thermal properties metals. Also: malleable (easily bent/moulded) And: ductile (which means they can be stretched out as in wire).

Question 29

What is an alloy?

Answer 29

And alloy is a mixture of two or more metals. They are used to strengthen or to provide different properties to the main metal. The added element disturbs the regular arrangement of the pure metal so that the atoms do not slide over one another so easily.. For example mixing iron with carbon creates steel.

Question 30

Conservation of mass as used in chemistry.

Answer 30

The total mass of the products is equal to the total mass of the reactants. In other words what goes in must come out. This is why we use chemical equations to show that both sides must balance.

Question 31

What is a half equation?

Answer 31

A half equation shows what happens to a reactant with a focus on its electrons.

The key here is to count the number of missing electrons.

E.g., if iron is put into copper (II) sulphate, the iron loses 2 electrons: Fe_(s) -> Fe_(aq) ²⁺ + 2e^-.

Question 32

What is Relative Formula Mass? (M_r)

Answer 32

The sum of all the relative atomic masses (A_r)

E.g., C₂H₄0₂ (vinegar!)

A_r => C = 12, H = 1, O=16

C => 12 x2 = 24

H => 4 x 1 = 4

O => 16 x 2 = 32

THEREFORE M_r of vinegar C₂H₄0_{2 =} 60 [24+4+32]

Question 33

Why do some reactions show a change in mass (despite the theory of the conservation of mass)?

Answer 33

Not all chemical reactions take place in closed systems.

So some gas molecules may leave the open or ‘non-closed’ system or react into it from the air.

E.g., heating Mg _(s) draws O_2(g) from the air, so 2Mg (s) -> 2Mg02(s)

While when calcium carbonat is heated, it gives off CO₂.

When the gases are ‘caught’ then the conservation of mass is secured.

Question 34

How to calculate the amount of a substance in mols given the mass of a substance?

Answer 34

amount in mols = mass in grammes / formula mass

E.g., We have 88 grammes of CO₂. Formula mass of CO₂ is 44.

No. of mols = 88/44

= 2

Question 35

HT: What is a mole (mol)?

Answer 35

It is a standardised measure of the number of particles in a substance.

The number of particles (atoms, ions, or molecules) is always 6.023 x 10²³. It is called Avagadro’s constant after the man who counted them all.

“Now we know how many moles it takes to fill the Albert Hall…” sung the Beatles in Day in the Life.

Sort of :)

Thankfully, the mass of one mol relates to the relative atomic mass of an element.

E.g., C₁₂ has a mass of 12g which is one mol of carbon.

O₁₆ has a mass of 16g, which is one mol of oxygen.

CO₂ has a mass of 44g, which is one mol of carbon dioxide.

Question 36

What is a limiting reactant?

Answer 36

When one of the reactants is completely used up in a reaction, it stops the reaction from continuing - hence it is a limiting reaction.

Question 37

How to measure the concentration of a solution?

Answer 37

Concentration = mass of a solute /volume of a solution

[solute = that which is to be dissolved; it needs to be soluble; it then makes a solution]

E.g., 2.00g solute (eg, salt) dissolved to form 1.00dm³ of solution (eg, water)

the concentration would simply be 2 /1 = 2 g/dm³ (salt water or brine)

If 5.00g of solute dissolved to form 2.00dm³ of solution,

the concentration would be 5/2 = 2.5g/dm³

Question 38

What are the properties of ionic compounds?

Answer 38

Giant structures of ions
Held together by strong forces of attraction
* high melting and boiling points
* do NOT conduct electricity when solid

* DO conduct when molten (ions are then free to move around - ions are charged particles!)

Question 41

Describe Giant Covalent Structures and give an example or two

Answer 41

Giant covalent structures
* linked by strong covalent bonds
* high melting and boiling points

E.g., diamonds (carbon allotrope) have
* rigid covalent LATTICE structure
Each Carbon has four bonds
No charged particles
Does not conduct electricity
silicon dioxide - lattice structure like a diamond

GRAPHITE:
high mp and bp
carbons form 3 bonds
layers are held together by weak intermolecular forces
makes graphite soft and slippery
conducts electricity

Question 43

Describe polymers

Answer 43

Polymers
* large molecules
* synthetic
* molecules are held together by strong covalent bonds
* solid at room temperature
* cheap and strong

Question 44

Properties of metals

Answer 44

Properties of metals
* metallic bonds make them really strong
- useful for making structures
* electrons are delocalised
* good thermal and electrical conductors
* layers can slip over each other easily which makes metal malleable (bent and shaped)
* ductile - made into wires (duc- to lead)
* SOME METALS react with oxygen - RUST
Others do not react so quickly and hence are good for carrying water (e.g., copper)