Gypsum

Question 1

Rock mineral mined in virus parts of the world, and is nearly pure calcium sulfate dihydrate (CaSO4⋅ 2H2O)

Answer 1

Gypsum

Question 2

Dehydrate form of gypsum where all forms are obtained from

Answer 2

(CaSO4 . 2H2O)

Question 3

The heating and manufacturing process where the gypsum loses 1 1/2 moles of water of crystallization and is formed in the hemihydrate form of CaSO4

Answer 3

Calcination

Question 4

Chemical formula of the hemihydrate form of gypsum

Answer 4

(CaSO4)2 . H20

Question 5

What chemical reaction happens when the CaSO4 in the form of plaster, dental stone, or high-strength stone is mixed with water, and the hemihydrate is converted back to the dihydrate form?

Answer 5

Exothermic

Question 6

Heating process wherein the gypsum is heated at 110°C-120°C, and the production of steam with pressure changes the rock to a white powder form called plaster or β-hemihydrate.

Answer 6

Open calcination

Question 7

What do you call the powder formed from open calcination?

Answer 7

Plaster or β-hemihydrate

Question 8

Heating process that uses a closed container (autoclave) at 120°C-120°C, producing a yellow powder called dental stone or α-hemihydrate.

Answer 8

Closed calcination

Question 9

What do you call the powder formed from closed calcination?

Answer 9

Dental stone or α-hemihydrate

Question 10

The higher the temperature → the greater the pressure → the finer ____ particles are produced.

Yellow
White

Answer 10

Yellow

Question 11

Type of gypsum used to get a negative copy

Answer 11

Impression plaster (Type I)

Question 12

Other names for the Model Plaster (Type II).

Answer 12

Plaster of Paris
Alabaster
β-hemihydrate

Question 13

W:P ratio of the model plaster.

Answer 13

45 ml H2o/100 grams plaster
0.45 - 0.5

Question 14

Principal constituent of Type II gypsum

Answer 14

CaSO4 1/2 H2O (calcium sulfate hemihydrate)

Question 15

An accelerator of the model plaster, which increases the rate of reaction between powder and liquid, and reduces setting expansion

Answer 15

KSO4 (potassium sulfate)

Question 16

Medical uses of the model plaster

Answer 16

Immobilizing casts in case of fractures

Question 17

Commercial use of model plaster

Answer 17

Figurine making

Question 18

Dental uses of the model plaster

Answer 18

Model/study cast
Investing material
Mounting the upper and lower casts on the articulator

Question 19

Type of gypsum that is creamy white in color, in powder form, large, porous, spongy, and irregular in shape

Answer 19

Type II
Model plaster
Plaster of Paris

Question 20

Type of gypsum that is yellow in color, powder form, small, dense, and regular in shape

Answer 20

Type III
Dental Stone Class I

Question 21

Same as plaster, except that there is an increase in the concentration of accelerator and the presence of pigments

Answer 21

Type III
Dental Stone Class I

Question 22

Principal constituent of the (Type III) Dental Stone Class I

Answer 22

CaSO4 (calcium sulfate) hemihydrate

Question 23

Constituent of the dental stone class I that reduces water requirement when added

Answer 23

Lignosulfonate

Question 24

What constituent of dental sone is responsible of the faster setting?

Answer 24

Higher % OF KSO4 (potassium sulfate)

Question 25

W:P ratio of the Dental Stone Class I

Answer 25

28 ml of H2O/100 grams of powder (0.28 - 0.30)

Question 26

Type of gypsum that is bright yellow/aqua in color, in powder form, finer, dense, and more regular in shape than class I

Answer 26

Type IV Dental Stone Class II

Question 27

W:P ratio of Dental Stone Class II

Answer 27

24ml of H2O/100 grams powder

Question 28

Other names for the Dental Stone Class II

Answer 28

Die stone Dental stone of high strength Densite α-hemihydrate