lect 2 - physical properties

What are the building blocks of simple substances?

a) Single element

b) Multiple elements

c) Ionic compounds

d) Complex mixtures

Single element

What type of bond exists between different substances?

a) Cohesive bond

b) Covalent bond

c) Adhesive bond

d) Hydrogen bond

Adhesive bond

Which of the following is a secondary chemical bond?

a) Covalent bond

b) Ionic bond

c) Metallic bond

d) Van der Waals bond

Van der Waals bond

What is the property of changing the crystal lattice depending on temperature called?

a) Isotropy

b) Anisotropy

c) Allotropy

d) Rheology

Allotropy

Which materials are isotropic?

a) Crystalline substances

b) Gases

c) Solids only

d) Metals

Gases

How many calories are required to convert 1 gram of water from liquid to gas?

a) 420 calories

b) 540 calories

c) 360 calories

d) 600 calories

540 calories

What causes galvanism in dental restorations?

a) Unequal distribution of stress

b) Different electrical potentials of restorations

c) Corrosion of the material

d) High thermal conductivity

Different electrical potentials of restorations

What does thixotropy refer to?

a) Property of materials to retain their viscosity

b) Study of solid flow

c) Change in viscosity under applied pressure

d) High absorption capacity

Change in viscosity under applied pressure

What is sorption?

a) Adsorption + Absorption

b) Solubility

c) Diffusion

d) Adhesive property

Adsorption + Absorption

A wetting value of 0 indicates:

a) Poor wetting

b) Complete wetting

c) Partial wetting

d) High surface tension

Complete wetting

What is the unit for water sorption?

a) Micrograms per cubic millimeter

b) Grams per cubic centimeter

c) Milliliters per gram

d) Joules per cubic millimeter

Micrograms per cubic millimeter

What does a higher viscosity indicate?

a) Higher capillary penetration coefficient

b) Lower capillary penetration coefficient

c) Higher surface tension

d) Lower surface tension

Lower capillary penetration coefficient

At what temperature does feldspathic porcelain exhibit amorphous properties?

a) Below 1100°C

b) 1100–1200°C

c) Above 1200°C

d) Below 900°C

1100–1200°C

What does creep describe?

a) The tendency of liquids to move or flow

b) The gradual deformation or flow of solids over time

c) The transformation of materials due to heat stress

d) The spreading or movement of gas particles

The gradual deformation or flow of solids over time

Where does adsorption occur?

a) Inside the material

b) On the surface

c) Both inside and on the surface

d) None of the above

On the surface

What are the primary types of chemical bonds?

a) Hydrogen and ionic

b) Metallic, covalent, and ionic

c) Van der Waals and hydrogen

d) Cohesive and adhesive

Metallic, covalent, and ionic

What is a cohesive bond?

a) A bond between different substances

b) A bond within atoms or molecules of the same substance

c) A bond formed due to polarity differences

d) A temporary bond formed under stress

A bond within atoms or molecules of the same substance

What are the four aggregate states of matter?

a) Solid, liquid, gas, and crystal

b) Solid, liquid, plasma, and amorphous

c) Solid, liquid, gas, and plasma

d) Liquid, gas, gel, and foam

Solid, liquid, gas, and plasma

Which of the following describes isotropic materials?

a) Properties differ based on direction of applied force

b) Properties remain consistent regardless of direction

c) Materials change state under stress

d) Materials exhibit thixotropic behavior

Properties remain consistent regardless of direction

What materials are typically anisotropic?

a) Amorphous substances

b) Liquids and gases

c) Crystalline substances

d) Colloidal systems

Crystalline substances

What is thermal conductivity?

a) Ability to transfer electrical charge

b) Ability to conduct heat without changing aggregate state

c) Resistance to heat flow

d) Capacity for thermal expansion

Ability to conduct heat without changing aggregate state

What happens when the surface tension of a liquid is high?

a) The penetration coefficient increases

b) The penetration coefficient decreases

c) The wetting improves

d) The material exhibits high thixotropy

The penetration coefficient decreases

What property does thixotropy describe?

a) Fluids becoming more viscous under pressure

b) Fluids changing viscosity when pressure is applied

c) Solids retaining shape under high stress

d) Crystals aligning under magnetic fields

Fluids changing viscosity when pressure is applied

What is a colloid system?

a) A solution with evenly distributed particles

b) A mixture with two or more phases where one phase has particles larger than molecular size

c) A liquid-gas interaction forming foam

d) A crystalline solution with high viscosity

A mixture with two or more phases where one phase has particles larger than molecular size

What is a sol?

a) A semi-solid phase formed from cooling a liquid

b) A colloidal solution with particles dispersed in a liquid

c) A solid state with dispersed particles

d) A solution exhibiting gel properties

A colloidal solution with particles dispersed in a liquid

What does a higher surface tension indicate?

a) Lower viscosity

b) Higher penetration coefficient

c) Higher capillary penetration coefficient

d) Better wetting

Higher capillary penetration coefficient

At what temperature range does feldspathic porcelain become amorphous?

a) Below 900°C

b) 1000–1100°C

c) 1100–1200°C

d) Above 1300°C

1100–1200°C

What is the role of viscosity in capillary penetration?

a) High viscosity leads to high penetration coefficients

b) High viscosity decreases penetration coefficients

c) Viscosity has no effect on penetration

d) Viscosity enhances wetting

High viscosity decreases penetration coefficients

What is the process of adsorption?

a) Holding particles on the surface

b) Holding particles inside the material

c) Absorption + desorption

d) Loss of particles due to external forces

Holding particles on the surface

What does a high wetting value represent?

a) Good wetting

b) Complete wetting

c) Poor wetting

d) Moderate wetting

Poor wetting

What does rheology study?

a) Solid elasticity

b) Diffusion of liquids

c) Fluidity and deformation of materials

d) Thermal conductivity

Fluidity and deformation of materials

What is the temperature range at which wax exhibit amorphous properties?

a) Below 36°C

b) Above 52°C

c) 36–52°C

d) Below 25°C

Above 52°C

What unit is used to measure water sorption in dental materials?

a) Milligrams per gram

b) Micrograms per cubic millimeter

c) Grams per cubic centimeter

d) Micrograms per liter

Micrograms per cubic millimeter

How is capillary penetration determined?

a) By measuring surface tension

b) By determining the rise of the liquid in a tube

c) By calculating wetting angles

d) By assessing viscosity changes

By determining the rise of the liquid in a tube

What is creep?

a) A liquid property describing flow resistance

b) A solid's ability to flow over time under stress

c) A gas property describing compressibility

d) A thermal property of crystalline materials

A solid's ability to flow over time under stress

Which of the following describes absorption?

a) Particles held on the surface

b) Particles held within the substance

c) Loss of energy from the surface

d) Diffusion through the surface

Particles held within the substance

What is polymorphism?

a) Change in thermal conductivity with temperature

b) Change in crystal structure depending on temperature

c) Variation in mechanical properties with direction

d) Resistance to mechanical stress

Change in crystal structure depending on temperature

What type of bond is present in metallic substances?

a) Ionic

b) Covalent

c) Metallic

d) Van der Waals

Metallic

What is the penetration coefficient?

a) The measure of wetting ability

b) The degree to which a liquid penetrates a material

c) The ratio of viscosity to surface tension

d) The difference between adsorption and absorption

The degree to which a liquid penetrates a material

What does complete wetting correspond to in terms of wetting angle?

a) 180 degrees

b) 90 degrees

c) 45 degrees

d) 0 degrees

0 degrees

What is an adhesive bond?

a) A bond between atoms in the same molecule

b) A bond between atoms in different molecules

c) A bond between different substances

d) A temporary bond during gel formation

A bond between different substances

What causes polymorphism in materials?

a) Changes in pressure

b) Variation in external forces

c) Differences in chemical bonding

d) Changes in temperature

Changes in temperature

What is the term for the combined processes of adsorption and absorption?

a) Cohesion

b) Adhesion

c) Sorption

d) Diffusion

Sorption

What happens when viscosity of a material increases?

a) The material's fluidity increases

b) The material's fluidity decreases

c) The surface tension decreases

d) The material becomes more isotropic

The material's fluidity decreases

What is the primary difference between adsorption and absorption?

a) Adsorption occurs on the surface; absorption occurs within the material

b) Adsorption occurs within the material; absorption occurs on the surface

c) Adsorption is irreversible, absorption is reversible

d) Adsorption involves gases, absorption involves liquids

Adsorption occurs on the surface; absorption occurs within the material

Which of the following is NOT an aggregate state?

a) Liquid

b) Plasma

c) Gel

d) Solid

Gel

What does a low wetting angle indicate?

a) Poor wetting

b) Good wetting

c) Incomplete wetting

d) High surface tension

Good wetting

What does a higher surface tension generally result in?

a) Increased capillary penetration

b) Decreased capillary penetration

c) Reduced wetting ability

d) Enhanced wetting ability

Increased capillary penetration

What is the key characteristic of crystalline substances?

a) Isotropic properties

b) Anisotropic properties

c) Amorphous lattice structure

d) High thermal conductivity

Anisotropic properties

What is the key characteristic of crystalline substances?

a) Isotropic properties

b) Anisotropic properties

c) Amorphous lattice structure

d) High thermal conductivity

Anisotropic properties

What is a gel in colloidal systems?

a) A solution with solid particles dispersed in a liquid

b) A semi-solid phase formed through cooling or chemical reaction

c) A liquid with suspended crystalline particles

d) A foam with entrapped air bubbles

A semi-solid phase formed through cooling or chemical reaction

What factor primarily determines capillary penetration?

a) Surface area

b) Degree of liquid rise

c) Thermal expansion coefficient

d) Polarity of the liquid

Degree of liquid rise

At what temperature does wax show crystalline properties?

a) Below 36°C

b) 36–50°C

c) 50–60°C

d) Above 60°C

Below 36°C

What type of bond involves the sharing of electrons?

a) Ionic bond

b) Metallic bond

c) Covalent bond

d) Hydrogen bond

Covalent bond

What are the building blocks of complex substances?

a) Single elements

b) Multiple elements

c) Molecules only

d) Crystals

Multiple elements

Which of the following best describes rheology?

a) Study of mechanical strength in materials

b) Study of elasticity and rigidity

c) Study of deformation and flow of materials

d) Study of chemical reactions in liquids

Study of deformation and flow of materials

What is the typical behavior of amorphous substances?

a) They are isotropic

b) They are anisotropic

c) They exhibit high melting points

d) They have a crystalline structure

They are isotropic

What happens to feldspathic porcelain above 1200°C?

a) It remains amorphous

b) It becomes crystalline

c) It decomposes into gas

d) It becomes isotropic

It becomes crystalline

What effect does increasing temperature generally have on surface tension?

a) Increases surface tension

b) Decreases surface tension

c) No effect on surface tension

d) Enhances wetting

Decreases surface tension

Which bond type contributes to van der Waals forces?

a) Ionic bonds

b) Secondary chemical bonds

c) Metallic bonds

d) Primary covalent bonds

Secondary chemical bonds

What is the relationship between thixotropy and viscosity?

a) Thixotropy increases viscosity permanently

b) Thixotropy decreases viscosity permanently

c) Thixotropy causes reversible changes in viscosity

d) Thixotropy has no effect on viscosity

Thixotropy causes reversible changes in viscosity

How is wetting angle measured?

a) By observing fluid rise in a capillary

b) By calculating the contact angle between the liquid and surface

c) By measuring the viscosity of a liquid

d) By determining the thermal conductivity

By calculating the contact angle between the liquid and surface

What happens to capillary penetration if viscosity increases?

a) Penetration increases

b) Penetration decreases

c) Penetration remains constant

d) Viscosity has no effect on penetration

Penetration decreases

What materials are characterized by amorphous properties?

a) Crystalline substances

b) Solids only

c) Gases and liquids

d) Glass and polymers

Glass and polymers

What is the role of temperature in rheological properties?

a) Temperature has no effect on rheology

b) Temperature stabilizes fluid viscosity

c) Temperature alters fluidity and deformation behavior

d) Temperature causes material anisotropy

Temperature alters fluidity and deformation behavior