Chapter 1: Materials in Our World

Question 1

What is a material

Answer 1

a material is a substance used to make objects e.g wood is used to make houses.

• substances that don’t count is HCL or CO2 because they aren’t used to make objects

Question 2

What are elements

Answer 2

elements are substances made of atoms containing the same amount of protons / atomic number

Question 3

What are compounds

Answer 3

compounds are pure substances made of more than one type of atom, containing more than one element in fixed proportions

Question 4

What is a pure substance

Answer 4

a pure substance is a sample of matter that only contains one type of compound or atom e.g pure gold, pure water, pure sodium chloride

Question 5

What is an alloy and why are they used

Answer 5

a mixture of a two metals or a metal and a small amount of a non metal

iron is naturally soft and corrodes easily, but when alloyed with carbon it is much stronger and corrosion resistant

Question 6

what is a polymer and why are they used

Answer 6

a molecular structure composed of many repeating smaller units bonded together

e.g plastics and latex are polymers and are used due to their low density, electrical insulation and corrosion resistance

compatibility with human tissue

Question 7

What is a ceramic and why are they used explain crystalline vs amorphous

Answer 7

inorganic non metallic solid. metal, non metal and metalloid substances bonded together covalently

crystalline - highly ordered

amorphous - highly irregular

e.g porcelain, silicon and carbide used for high compressive strength, temperature resistance, insulating, semi conductor or super conductor

Question 8

What is a composite material

Answer 8

a combination of two or more distinct materials with significantly different physical and chemical properties

e.g reinforced concrete is concrete containing steel bars which supplements the concretes relatively low tensile strength while keeping the compressive strength of concrete

Question 9

What is nanoscale and how big is a nanometre

Answer 9

structures between 1-100 nanometres are considered nanoscale

a nanometre is 1 billionth of a metre (10^-9m)

Question 10

what is top-down fabrication + pros and cons (1 each)

Answer 10

material starts bigger than desired

material is selectively removed or size is reduced until desired shape is achieved

e.g computer chips and sunscreen

cheap and mass produced. limited to simple structures

Question 11

what is bottom-up fabrication + pros and cons (1 each)

Answer 11

physically building or growing the material atom by atom

self assembling nanomaterials

complicated structures but cannot be mass produced

Question 12

what is a nanoparticle + examples

Answer 12

spherical particles with diameter from 1-100nm

different properties form their bulk forms due higher surface area to volume ratios

used in stained glass or ceramics to obtain different colours at different sizes

Question 13

What is sieving

Answer 13

separation by particle size

separating solids of different sizes using a sieve which only allows particles smaller than the holes to pass

Question 14

What is filtration

Answer 14

separation by particle size

used to separate solids from a liquid or gas

pool filters, coffee filters

Question 15

explain filtrate and residue

Answer 15

the filtrate is the liquid that collects in the flask

the residue is the solids collected in the filter paper

Question 16

what is vacuum filtration

Answer 16

Buchner funnel is ceramic and has holes at the bottom and filter paper on top

the liquid flows through the funnel as the vacuum connected to the flask pulls

dries the filtrate quicker and is faster than gravitational filtration

Question 17

what is sedimentation

Answer 17

separation by density

sedimentation is when you let a mixture of solids and liquids sit

this allows gravity to pull the denser objects to the bottom and then the finer ones rest on top

water treatment plants use this as a cheap way to separate large volumes of solids and liquids

Question 18

what is decantation

Answer 18

after the sediment has settled in the liquid you can pour out the liquid into another container

Question 19

how does liquids being immiscible allow them to be separated in a separation funnel

Answer 19

separation by density

immiscible is when two liquids cant mix

so when the mixture has two liquids that are immiscible and different densities and is allowed to sit the liquids will separate themselves in layers

the flask can then be opened allowing the denser liquid to flow out first

e.g oil and water are immiscible

Question 20

what is centrifugation

Answer 20

separation by density

spinning a mixture very quickly (20000rpm) separates the less dense particles from the more dense through centrifugal force

speeded up version of sedimentation

Question 21

what is evaporation

Answer 21

separation by boiling point

used when solids dissolve into a liquid

the solution is boiled so that the liquid evaporates and the solid is left behind

Question 22

explain solute vs solvent

Answer 22

solute - dissolved solid

solvent - the liquid

Question 23

explain what fractional distillation is

Answer 23

same as regular distillation but has a fractioning column with high surface area beads

allows the more volatile component to exit as vapour at the top and the less volatile to condense back into the distillation flask

Question 24

what is electrostatic separation

Answer 24

separation by electric charge

objects with opposite charge attract (electrostatic attraction)

therefore electrostatic attraction can be used to separate charged particles from uncharged

electrostatic filters can separate smoke particles from waste gases by passing the smoke through an negatively charged grid so that the smoke particles have a negative charge

they can then by attracted by the positively charged electrodes to collect the smoke particles