Choosing materials - SC26

Question 1

What are ceramics?

Answer 1

range of durable compounds that change very little when heated

Question 2

what are the properties of ceramics?

Answer 2

chemically unreactive, hard and stiff, brittle, poor electrical and thermal conductors, high melting points

Question 3

what is the structure of ceramics

Answer 3

giant structures with many covalent or ionic bonds

Question 4

what are types of clay ceramics?

Answer 4

brick, porcelain and china

Question 5

how are clay ceramics formed?

Answer 5

clay is heated to a very high temperature and tiny crystals form and join together

Question 6

how are porcelain and china formed from clay?

Answer 6

after crystals form and join together, they are dipped in a glaze and heated strongly again

Question 7

how is glass made?

Answer 7

by melting sand then allowing it to cool and solidify

Question 8

why are glass and clay ceramics similar?

Answer 8

they both have giant structures which means they have the similar properties

Question 9

What in the structure of glass differs from that of clay ceramic, what is the end result?

Answer 9

atoms in glass are not arranged in a regular way to form crystals so glass is transparent instead of opaque

Question 10

describe the steps in the float process for modern window glass?

Answer 10

molten glass is poyred onto a bath of moletn tin where it spreads out on the surface. The flat layer of glass is drawn away and cooled in a continuous process

Question 11

why are polymers a good choice for material?

Answer 11

they can be moulded into complex shapes - they are chemically unreactive and strong

Question 12

why would polymers not be a good choice of material?

Answer 12

poor electrical and thermal conductors

Question 13

What is rigid PVC good for?

Answer 13

underground pipes and window frames

Question 14

how can PVC be made softer?

Answer 14

using plasticisers

Question 15

what is flexible PVC used for?

Answer 15

indoor water pipes and waterproof flooring

Question 16

what are the properties of metals?

Answer 16

strong, hard, shiny, high melting points, good electrical and thermal conductors. malleable

Question 17

what do different metal elements mix together to form?

Answer 17

alloys

Question 18

how do alloys differ from metals?

Answer 18

stronger

Question 19

what does electroplating metal with unreactive metal allow?

Answer 19

improve appearance or resistance to corrosion

Question 20

what is a composite material?

Answer 20

mixture of 2 or more materials, combined to produce a material with improved properties

Question 21

What is true about the materials used in composite materials?

Answer 21

they have contrasting properties, are visable in the composite materal and can often be seperated out by physical seperation methods

Question 22

how is contrete made?

Answer 22

mixing cement, sand, aggregate and water together.

Question 23

what happens as contrete sets hard?

Answer 23

chemical recations happen that bond the solid components together. The sand and aggregate form the reinforcement of the concrete

Question 24

what is the reinforcement in concrete bonded together by? what does this form

Answer 24

by cement which forms the matrix

Question 25

what is tensile strength?

Answer 25

resist being stretched

Question 26

why are glass fibres good as a reinforcement?

Answer 26

low density and high tensile strength

Question 27

what is compressive strength a measure of?

Answer 27

how well a material resists being squashed

Question 28

what is concrete strong / weak in?

Answer 28

strong in compression, weak in tension

Question 29

what is concrete suitable for?

Answer 29

road surfaces and foundations

Question 30

What material reinforces contrete, what is the effect?

Answer 30

steel bars are strong in tension and so the contrete resists cracking better than concrete alone (contrete now strong in tension and compression)

Question 31

why is steel-reinforced concrete better than regular?

Answer 31

strong in tension and compression, less dense + cheaper than steel alone

Question 32

what is wood composed of as a natural composite material?

Answer 32

cellulose fibres in a matrix of ploymer called lignin

Question 33

When is wood stronger?

Answer 33

along the grain rather than across the grain

Question 34

How is plywood constructed?

Answer 34

odd numbers of thin sheets of wood, each glued at right angles to the sheet below

Question 35

What is wood’s tensile strength along the grain?

Answer 35

80

Question 36

what is wood’s tensile strength across the grain?

Answer 36

4

Question 37

what is plywood’s tensile strength?

Answer 37

25-40