Advanced Food Processing Unit Operations Questions and Answers on “Crystal Growth”.
1. What causes crystal growth?
a) Vapor
b) Solute
c) Melt
d) Vapor, solution and melt
Answer: d
Clarification: Crystals grow in one of three major ways; they are from a vapor, from a solution and from a melt where few molecules or ions come near each other in an appropriate orientation to form a stable submicroscopic aggregate.
2. Why is crystal growth important?
a) Increase the value of the product
b) Increase the size of the compound
c) Information about the structure of compounds
d) Information regarding the quality of product
Answer: c
Clarification: Crystals are very important and one of the reasons for the importance is that they give us information regarding the structure of compounds and also the function of the crystals and its effect on other compounds.
3. Which crystal grows the fastest?
a) Table salt
b) Epsom salt
c) Ferro sulphate salt
d) Sea salt
Answer: b
Clarification: The simplest and fastest crystals to grow are the Epsom salt (magnesium sulfate) crystals. These salts are used as healing agent and pain reliever.
4. Are crystals grown in cold temperature?
a) True
b) False
Answer: a
Clarification: Warm temperature helps in water evaporation which causes the crystals to grow more quickly. Crystals will still grow in cooler temperatures, but take longer time for the water to evaporate.
5. What is the purpose of seed crystal in crystal growth?
a) Nucleation center
b) Catalyst
c) Solvent
d) Solution
Answer: a
Clarification: The seed crystal acts as a nucleation center for the crystal and it promotes the growth of crystal. The orientation of seed crystal regulates the orientation of crystals.
6. Which of the following statements about frozen water are correct?
Statement 1:Water molecules slowed down and arrange themselves into fixed positions.
Statement 2: Water molecules freeze in a triangle pattern.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: a
Clarification: When water freezes, the water molecules slowed down arrange themselves into fixed positions. Water molecules freeze in hexagonal pattern and the molecules are further apart than they were in liquid water. The molecules in ice vibrate.
7. What happens when a crystal grows in size?
a) It becomes softer
b) It becomes smoother
c) It becomes rough
d) It becomes coarsely
Answer: b
Clarification: As a crystal grows, new atoms attribute easily to the rougher and less stable parts of the surface, but less easily to the flat and stable sides. Therefore, the flat surfaces tend to grow larger and smoother, until the whole crystal surface consists of these plane surfaces.
8. At what temperature do ice crystals form?
a) Lower than 0°C
b) More than 0°C
c) At 0°C
d) At 4°C
Answer: a
Clarification: There are a number of ways in which ice crystals can form at temperature lower than 0°C. One method contains the rare presence of a particle known as an ice nucleus within a water droplet that acts as a catalyst for freezing.
9. How to prevent sugar from crystallizing?
a) By evaporating
b) By boiling
c) By adding an interferent
d) By adding an humectant
Answer: c
Clarification: The crystallization process is prevented by adding an interferent, like acid (vinegar, lemon and tartaric) and also corn syrup and glucose during the boiling procedure.
10. Is crystallization dependent on agitation?
a) True
b) False
Answer: a
Clarification: The agitation rate had a noticeable effect on size of the crystal. Higher the agitation rates, smaller is the crystal size. The lesser or no agitation leads to bigger size in crystals.