Found Objects - The Stone Age

Question 1

What are stone tools made from?

Answer 1

Materials that can be fractures / snapped, commonly flint or chert

Can be any stone capable of being chipped into shape

Question 2

What was the preferred material for making tools?

Answer 2

Obsidian, metamorphic form of volcanic glass, not available in UK e.g. Melos

Question 3

What is flint and where is it found

Answer 3

Chert
In sedimentary rocks - chalk / limestone (CaCO3)

Flint is essentially quarts, consists of Si-O tetrahedra, SiO2

Question 4

How is SiO2 said to be formed

Answer 4

• Chalk found by deposition of dead organisms, sedimented into sea 75 mill yrs ago
• in top 5m, layer of biogenic silica produced by sponges, diatoms… precipitated out at an toxic/ anoxic boundary 10m below surface
• as flint nodules sank through sea floor became purer and contained less defects

Question 5

Flint knapping

Answer 5

Flint is chipped (knapper) into shape, any defects might interfere with the direction of fracture passing through the material

Question 6

Where was the best flint for snapping found?

Answer 6

At the base of the flint layer, mine further for better quality flint e.g. neolithic flint mine, Grimes Graves Norfolk, deepest pits 14m

area has 433 sunken shafts

Question 7

What is a crystalline material?

Answer 7

Has a grain structure

Question 8

What is amorphous

Answer 8

glassy, no grain structure, and no long-range order e.g. obsidian

Question 9

What is ‘cryptocrystalline’ and what materials are described as such

Answer 9

no grains, sheer planes e.g. flint and chert

means material will fracture in a manner directed by the application of a force of a blow –> conchoidal fracture

Question 10

What happens when a blow is applied to a rock

Answer 10

Shock wave is generated and passes through the material gradually dies away.

Shock wave is sinusoidal, 1st peak is the largest

Question 11

If the forces are sufficient the flint will fracture following the sinusoidal shape, describe the shape

Answer 11

• !st peak of shockwave occurs immediately below point of blow (platform)
• produces the largest ripple-shaped fracture in the flint –> bulb of percussion (characteristic sign of a man-made flint)
• ripples are known as ‘radial ridges’

Question 12

How are more delicate tools made

Answer 12

using ‘soft hammers’ e.g. dear antlers, to transmit blow to the flint

or pressure flaking, application of a point to the flint with increasing pressure until flint failed and fractured

Question 13

Describe a further method of improving the flint

Answer 13

Heat it to 300- 400oC for several hours, improves “flakeability”

Question 14

What was earlier than the extraction of metals

Answer 14

the processing of metals

Question 15

Most metals are found in a compound e.g. FeO, some exist in pure state and can be processed straight away, give 2 examples

Answer 15

gold and native copper

Question 16

Why can pure metals be processed straight away

Answer 16

relatively low mp (1064oC), inertness, won’t react with container when melted to become liquid or corrode or oxidise in local environment

ductility = beaten into sheets and wires without breaking

Question 17

Describe the properties of a single crystal of native Cu

Answer 17

more ductile, but less strength –> variations in properties even in what seems to be a homogeneous material

Question 18

Describe the properties of Polycrystalline materials

Answer 18

Tend to be STRONG but not so DUCTILE

Question 19

How can Cu be strengthened

Answer 19

Ductility can be reduced by working or hammering of pure CU = WORK HARDENING

Question 20

What happens during plastic deformation

Answer 20

Material is being stretched

Initially deforms elastically, then plastically

represented on a stress-strain curve

Question 21

What happens as a metal is plastically deformed

Answer 21

defects are introduced into the crystal lattice = dislocations

dislocations = lines of discontinuity in the crystal lattice that are created by the application of force

Question 22

Describe an edge dislocation

Answer 22

Where an extra half-plane of atoms is created in the lattice, common in metals, created by an applied force, causing them to move around the lattice structure

By moving round structure, allow metal to deform and change shape, as deformation proceeds dislocations are created and forced to move

dislocations interact, can’t move past each other, more force must be applied until they do

yield strength appears to get stronger = WORK HARDENING

Question 23

When and where was work hardening of Cu first used

Answer 23

9000 BC in Middle East

Question 24

What does work hardening do?

Answer 24

Raises yield strength

Question 25

What is annealing?

Answer 25

Material can be heated and allowed to cool down very slowly

Question 26

What effect does heating have on work hardening?

Answer 26

Increases the rate of diffusion, hence increases mobility of the dislocations

becoming more mobile they can become shorter and climb up into the grain boundary, or move through crystal structure until dislocations of opposite sign meet and annihilate

Question 27

Name the 3 forms of pure copper (attractive, found minerals were worked and polished for decorative purposes)

Answer 27

• copper sulphides
• copper carbonates
• copper oxide

Question 28

Name the two types of copper sulfides

Answer 28

Chalcopyrite and Chalcocite (lustrous grey)

Question 29

Name the 2 copper carbonates

Answer 29

azurite (deep blue)

malachite (green)

Question 30

Name the copper oxide

Answer 30

cuprite (deep red)

Question 31

When was the first metal extracted from its ore

Answer 31

Copper in 5th - 6th millennia BC by Vinca Culture of Danube, in modern Serbia

Question 32

What began the Chalcolithic period

Answer 32

Use of copper grew out the needs of the Neolithic people, and use combined with flints resulted in the period being called the Chalcolithic

Question 33

How can Cu be obtained from the ore?

Answer 33

By heating up the ore, resulting in dissociation from the compound in which It was found, leaving behind pure Cu

Extraction of Cup done by heating ore in the presence of charcoal

Question 34

What does the Ellingham diagram show

Answer 34

The readiness of elements to bond to oxygen

Question 35

What are the x and y axis on an ellingham diagram

Answer 35

X axis = Temperature

Y axis = Change in Gibbs Free Energy

Question 36

What is the common line for elements on the Ellingham diagram

Answer 36

Most element oxides have line running upwards from left to right

Indicates the element becomes less strongly bonded to O as T increases

Question 37

How does the line for CO on an Ellingham diagram run?

Answer 37

runs in opposite direction to other elements.

As T increases C is more strongly bound to O, CO line passes over lines for other oxides

C has greater affinity for O than Oxides lines passed over

Question 38

What can C reduce

Answer 38

C can reduce CuO to pure Cu, for working and alloying at apps 100oC, above this temperature reduction of CuO is faster