Lecture 9: Metal alloys

What kind of ions do metals typically form?

a) Negatively charged

b) Positively charged

c) Neutral ions

d) Double ions

b) Positively charged

What is a metalloid?

a) A non-metal element

b) An element with both metallic and non-metallic properties

c) A highly reactive metal

d) A noble gas

b) An element with both metallic and non-metallic properties

Which of the following is an example of a metalloid?

a) Gold

b) Antimony

c) Mercury

d) Platinum

b) Antimony

Amphoteric substances exhibit which characteristics?

a) Only basic

b) Only acidic

c) Both basic and acidic

d) Neither basic nor acidic

c) Both basic and acidic

What metal can substitute mercury in amalgam due to its low melting point?

a) Gallium

b) Tin

c) Silver

d) Aluminum

a) Gallium

When is a crystal lattice formed?

a) In the gaseous state

b) In the liquid state

c) On passing into the solid state

d) On heating metals

c) On passing into the solid state

What effect does increasing temperature have within a crystal lattice?

a) Reduces oscillations

b) Stops oscillations

c) Increases oscillations

d) Has no effect

c) Increases oscillations

What is annealing?

a) Cooling a metal rapidly

b) Heating a metal to release accumulated stresses

c) Melting an alloy completely

d) Freezing a metal to retain stresses

b) Heating a metal to release accumulated stresses

What are the requirements for high noble metals?

a) At least 25% gold and 60% noble metals

b) At least 40% gold and 60% noble metals

c) At least 10% gold and 50% noble metals

d) At least 50% gold and 70% noble metals

b) At least 40% gold and 60% noble metals

Type III alloys are characterized as:

a) Soft and used for inlays

b) Hard and used for crowns and bridges up to three units

c) Medium-hard and used for overlays

d) Rigid and used for partial dentures

b) Hard and used for crowns and bridges up to three units

What is the karat value of pure gold?

a) 22 karats

b) 18 karats

c) 24 karats

d) 14 karats

c) 24 karats

The percentage of gold in extremely hard gold alloys ranges between:

a) 42-58%

b) 62-68%

c) 60-70%

d) 75-78%

c) 60-70%

Eutectic is defined as:

a) The highest melting point of an alloy

b) The specific ratio of metals in an alloy with the lowest melting point

c) A mixture with non-metal properties

d) A process for alloy purification

b) The specific ratio of metals in an alloy with the lowest melting point

How many crystal lattices exist?

a) 7

b) 10

c) 14

d) 20

c) 14

What are the requirements for noble alloys?

a) Less than 25% precious metals

b) More than 25% precious metals

c) Exactly 25% precious metals

d) No precious metals

b) More than 25% precious metals

What percentage of gold is found in soft gold alloys?

a) 60-70%

b) 75-78%

c) 80-90%

d) 42-58%

c) 80-90%

What is the percentage of gold in pale or economic gold alloys?

a) 100%

b) 80-90%

c) 42-58%

d) 62-68%

c) 42-58%

What color indicates insufficient palladium in gold alloys?

a) White

b) Yellow

c) Red

d) Rose

b) Yellow

What is the fineness of pure gold?

a) 500

b) 750

c) 1000

d) 850

c) 1000

What are the characteristics of Type II alloys?

a) Soft and used for inlays

b) Medium-hard and used for onlays, overlays, and crowns

c) Rigid and used for multi-unit bridges

d) Hard and used for crowns and small bridges

b) Medium-hard and used for onlays, overlays, and crowns

Which process is used for relieving accumulated stress in cold-worked metals?

a) Quenching

b) Annealing

c) Forging

d) Casting

b) Annealing

What is the primary use of Type IV alloys?

a) Crowns and small bridges

b) Inlays

c) Multi-unit bridges and partial dentures

d) Overlays

c) Multi-unit bridges and partial dentures

What is the role of palladium in gold alloys?

a) Increases malleability

b) Changes the color to white

c) Decreases hardness

d) Reduces melting point

b) Changes the color to white

What happens to the amplitude of oscillations in a crystal lattice as temperature increases?

a) It decreases

b) It remains constant

c) It increases

d) It becomes irregular

c) It increases

What is the melting point characteristic of a eutectic alloy? a) Highest possible melting point

b) Average melting point

c) Lowest possible melting point

d) Constant temperature

c) Lowest possible melting point

What is the percentage of gold in medium-hard gold alloys? a) 80-90%

b) 62-68%

c) 75-78%

d) 60-70%

c) 75-78%

What is the percentage of gold in hard gold alloys?

a) 60-70%

b) 62-68%

c) 75-78%

d) 42-58%

b) 62-68%

What are the characteristics of Type I alloys?

a) Hard and used for crowns

b) Soft and used for inlays

c) Rigid and used for multi-unit bridges

d) Medium-hard and used for onlays

b) Soft and used for inlays

What type of metals are required for non-noble alloys?

a) More than 40% noble metals

b) At least 60% noble metals

c) Less than 25% noble metals

d) No noble metals at all

c) Less than 25% noble metals

Which property defines a eutectic alloy?

a) High durability

b) Maximum hardness

c) Lowest melting point at a specific ratio of metals

d) Increased malleability

c) Lowest melting point at a specific ratio of metals

What are crystal lattices?

a) Structures formed during alloy cooling

b) Structures formed when metals solidify

c) Arrangements formed when metals heat up

d) Patterns formed due to chemical reactions

b) Structures formed when metals solidify

How many types of crystal lattices exist?

a) 7

b) 10

c) 12

d) 14

d) 14

What is the primary usage of Type II alloys?

a) Inlays

b) Crowns and small bridges

c) Multi-unit bridges

d) Onlays and overlays

d) Onlays and overlays

Which process involves heating metals to release accumulated stress without melting?

a) Casting

b) Annealing

c) Welding

d) Hardening

b) Annealing

What distinguishes noble alloys from high noble metals?

a) Noble alloys have less than 25% precious metals

b) High noble metals must have at least 40% gold

c) Noble alloys must have at least 50% gold

d) High noble metals contain no precious metals

b) High noble metals must have at least 40% gold

What is the primary property of amphoteric substances?

a) They resist corrosion

b) They show acidic and basic characteristics

c) They are highly malleable

d) They form eutectic alloys

b) They show acidic and basic characteristics

Which alloy type is suitable for partial dentures?

a) Type I

b) Type II

c) Type III

d) Type IV

d) Type IV

What is the main characteristic of rigid alloys?

a) Used for inlays

b) High ductility

c) Suitable for multi-unit bridges

d) Low melting point

c) Suitable for multi-unit bridges

What determines the color of gold alloys?

a) Ratio of silver to gold

b) Percentage of copper

c) Amount of palladium

d) Presence of tin

c) Amount of palladium

What is the characteristic ratio for a eutectic alloy?

a) Maximized strength

b) Lowest melting temperature

c) Highest melting temperature

d) Most malleable

b) Lowest melting temperature

What is the percentage of gold in yellow gold alloys with insufficient palladium?

a) 50-60%

b) 60-70%

c) 70-80%

d) The color is not related to gold percentage

d) The color is not related to gold percentage

Which metal is an example of an amphoteric substance?

a) Zinc

b) Iron

c) Gold

d) Mercury

a) Zinc

What type of alloy is used for multi-unit bridges?

a) Type I

b) Type II

c) Type III

d) Type IV

d) Type IV

Which process is used to change the hardness and ductility of metals?

a) Welding

b) Annealing

c) Tempering

d) Galvanizing

b) Annealing

What is the main advantage of using gallium as a substitute for mercury in amalgams?

a) High hardness

b) Non-toxic nature

c) Low melting point

d) High density

c) Low melting point

Which characteristic is required for a Type III alloy?

a) Soft and malleable

b) Medium-hard and ductile

c) Hard and strong for crowns and bridges up to three units

d) Rigid and used for partial dentures

c) Hard and strong for crowns and bridges up to three units

How does palladium content above 5% affect gold alloys?

a) Decreases durability

b) Increases malleability

c) Changes color to white

d) Lowers melting point

c) Changes color to white

What is the melting point behavior of a eutectic alloy?

a) Remains constant for all ratios

b) Lowest melting point at a specific ratio

c) Highest melting point at a specific ratio

d) Melts unevenly

b) Lowest melting point at a specific ratio

What is the characteristic of metals when transitioning into a solid state?

a) Formation of a liquid solution

b) Formation of a crystal lattice

c) Retention of the gaseous state

d) Increase in reactivity

b) Formation of a crystal lattice

What determines the rigidity of Type IV alloys?

a) Composition of precious metals

b) High density

c) Arrangement of the crystal lattice

d) Percentage of palladium

c) Arrangement of the crystal lattice

What is the typical percentage of gold in pale gold alloys?

a) 75-78%

b) 42-58%

c) 80-90%

d) 62-68%

b) 42-58%

How are crystal lattices influenced by temperature?

a) They dissolve at high temperatures

b) Their oscillations increase with temperature

c) They remain unchanged by temperature

d) They shrink as temperature increases

b) Their oscillations increase with temperature

What is the defining property of a Type I alloy?

a) Rigid and brittle

b) Hard and durable

c) Soft and used for inlays

d) Medium-hard for overlays

c) Soft and used for inlays

How many karats represent pure gold?

a) 18 karats

b) 20 karats

c) 24 karats

d) 22 karats

c) 24 karats

What is the effect of excessive stress on cold-worked metals without annealing?

a) Increased durability

b) Accumulation of internal stresses

c) Improved flexibility

d) Complete disintegration

b) Accumulation of internal stresses