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Physics A level > Testing and looking inside material > Flashcards

Testing and looking inside material Flashcards

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1
Q

Definition of strong

A

Takes a large stress to break

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2
Q

Definition of hard

A

Resistant to dents and scratches

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3
Q

Definition of tough

A

Can undergo a lot of plastic deformation after passing its elastic limit before breaking

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4
Q

Definition of brittle

A

Can only undergo little plastic deformations after passing its elastic limit before breaking

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5
Q

Definition of stiff

A

Is difficult to bend

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6
Q

Definition of malleable

A

Can easily be hammered or pressed into shape

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7
Q

Definition of ductile

A

Can easily be drawn into a wire

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8
Q

Units of strength

A

Pa

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9
Q

Units of hardness

A

Pa

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10
Q

Units of stress

A

Pa

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11
Q

Units of UTS

A

Pa

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12
Q

Units of toughness

A

Jm^-2

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13
Q

Equation for young modulus

A

stress/strain

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14
Q

Equation for stress

A

Force / area

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15
Q

Equation for strain

A

extension / length

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16
Q

Equation for UTS

A

maximum load / original area

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17
Q

Equation for the energy stored in a spring

A

Work done = 1/2ke^2

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18
Q

How do you find the energy stored in a spring from a force extension graph?

A

It’s the area under the line

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19
Q

Definition of elastic

A

A material that is able to regain its shape after being distorted

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20
Q

Definition of plastic

A

A material that has a low elastic limit and beyond that limit it doesn’t regain its original length/shape

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21
Q

Definition of yield strength

A

The amount of stress at which a material begins to deform plastically

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22
Q

What does Hooke’s Law say?

A

Force is proportional to extension, as long as the elastic limit is not exceeded

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23
Q

What is the equation linked to Hooke’s Law?

A

Force = spring constant X extension

24
Q

In Hooke’s Law, what does the spring constant show?

A

Shows how much force it takes to stretch a material (larger spring constant = stiffer material)

25
Q

What does crystalline mean?

A

That particles in a material are arranged in a regular pattern

26
Q

What does polycrystalline mean?

A

That within each grain of a material there is an ordered structure, but the orientation of each grain is random/disordered

27
Q

What does amorphous mean?

A

That a material has a disordered internal structure and a random orientation of each grain

28
Q

Definition of a lattice

A

A regular, repeated 3D arrangement of atoms/molecules in a crystalline solid

29
Q

Do bigger or smaller grains give a less efficiently packed material and why?

A

Bigger - because the grains can’t get as close to each other and so have bigger gaps in between

30
Q

Are metallic bonds directional or non directional?

A

Non-directional

31
Q

How strong are metallic bonds compared to ionic and covalent?

A

Similar to ionic, weaker than covalent

32
Q

Why do cracks blunten in metals?

A
  • Because they are ductile so the crack ‘stretches’ sideways.
  • And the layers absorb energy so extra would be needed to affect another layer
33
Q

Why are metals tough?

A

Their atoms are forced tightly together by their sea of electrons. The -ve mobile electrons keep the +ve ions in place.

34
Q

Why are metals stiff?

A

They have strong electrostatic attraction between the sea of electrons and ion lattice, forming strong metallic bonds

35
Q

What is UTS?

A

Ultimate tensile strength = the max stress a material can withstand before breaking

36
Q

Definition of yield stress (not yield strength)

A

The point at which a large amount of plastic deformation takes place with a constant load

37
Q

How does a material behave past its elastic limit?

A

It behaves plastically - would no longer return to its original shape once the stress was removed

38
Q

Why and how are alloys made?

A
  • Use atoms from a dif. metal to fill in dislocations
  • Increases stress needed to cause a slip
  • Makes the metal harder and less ductile
39
Q

What type of lattice do metals usually form?

A

A crystalline lattice

40
Q

What makes a metal stiff?

A

The electrostatic attraction between the ion lattice and free electrons form strong metallic bonds, making it hard to bend/stretch

41
Q

What makes a metal tough?

A

The strongly bonded lattice structure

42
Q

What makes a metal ductile?

A

The ions being able to move in the lattice when a force is applied

43
Q

What makes a metal hardER?

A

Alloying: fill dislocations in a metal with atoms from a dif. metal to make it harder for planes to slip as they require more stress

44
Q

What is alloying?

A

Filling dislocations in a metal with atoms from a dif. metal so that a greater stress is needed for planes to slip to strengthen a metal

45
Q

What happens to a metal’s microstructure when a force is applied to it?

A

The interatomic spacing between ions increases uniformly during elastic deformation. Once the stress is large enough for plastic deformation, the planes slip over each other

46
Q

What makes a metal need less stress than normal for its type to cause slipping?

A

If it has dislocations (is an imperfect metal)

47
Q

What type of lattice do ceramics form?

A

Mostly crystalline or polycrystalline, but sometimes amorphous

48
Q

What makes a ceramic more likely to have an amorphous structure and why?

A

If the molten ceramic is cooled very quickly; the atoms don’t have time to arrange regularly

49
Q

What features of a ceramic’s microstructure make them easy to fracture?

A

Their random atomic bonding means the lattice has no slip planes or mobile dislocations

50
Q

What makes a ceramic stiff?

A

Their strong bonds between atoms

51
Q

What type(s) of bonds do ceramics form?

A

Ionic or covalent

52
Q

What type of bonds to polymers make?

A

Covalent bonds

53
Q

What is a polymer?

A

A molecular chain made up of repeated monomers

54
Q

Polymer chains are often entangled, what makes them flexible?

A

The chains can be unravelled by rotating the monomers about their bonds when you pull them

55
Q

What are the 2 things the flexibility of a polymer dependent on?

A
  • How easily the monomers rotate about their bonds

- The strength and number of bonds between the chains

56
Q

Give an example of two materials together which make a composite material and name the composite material

A

e.g. steel + concrete make reinforced concrete

steel + glass make safety glass

57
Q

Give an example of two materials together which make a composite material and name the composite material

A

e.g. steel + concrete make reinforced concrete

steel + glass make safety glass

Physics A level (7 decks)

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