Food Packaging Technology Multiple Choice Questions & Answers (MCQs) on “Properties of Glass”.
1. Which of the following is used for the hot and surface treatment of glass?
a) Calcium Oxide
b) Zinc Oxide
c) Tin Oxide
d) Copper Oxide
Answer: c
Clarification: Tin Oxide is used for the hot and surface treatment of glass. It is an inorganic compound consisting of tin and oxygen. It is commonly used to create customized glass by giving transparent glass an opaque, porcelain-like, opaque appearance.
2. What are White flints?
a) Lacquered aluminum cans
b) Brown glass
c) Colorless glass
d) Translucent laminates
Answer: c
Clarification: Standard White flint glass is colorless. White flint glass is defined as a glass of high optical purity and low iron content. Made with the highest quality raw materials, super flint glass is produced using virgin batch materials. This means that more energy is required to melt the materials to the desired quality level.
3. A finish is a part of glass bottles where _________
a) labels are posted
b) cracks can never be formed
c) colors can never be applied
d) closures are applied
Answer: d
Clarification: Finish is a part of glass bottles where closures are applied. Finish is the part of the bottle that holds the cap or closure, the glass surrounding the opening in the container.
4. Which if the following is used to reduce coloration?
a) CeO2
b) TiO2
c) Na2S
d) Co3O4
Answer: a
Clarification: The addition of CeO2 (it is reduced to Ce2O3 by the radiations) in glasses in amounts up to 1.5% has proved an effective means of reducing coloration. Unfortunately, it is a very expensive oxide, so glass containers treated this way are significantly more costly than standard containers.
5. Which of the following is used to give amber color to glass?
a) CdS + Se
b) Cu2O + CuO
c) NiO
d) Na2S
Answer: d
Clarification: Na2S is used to give amber color to glass. CdS + Se is used to give orange color to glass. NiO is used to give purple color to glass. Cu2O + CuO is used to give blue color to glass.
6. Which of the following gives black color to glass?
a) MnO
b) CdS
c) Sb2S3
d) Co3O4
Answer: d
Clarification: Co3O4 (+ Mn, Ni, Fe, Cu, Cr oxides) gives black color to glass. Sb2S3 gives red color to glass. CdS gives yellow color to glass. MnO gives brown color to glass.
7. The principle of fracture analysis in glass is based on Young’s modulus.
a) True
b) False
Answer: a
Clarification: The given statement is true. The principles of fracture analysis or diagnosis of the cause(s) of glass container breakage has the following four aspects:
i. Internal pressure resistance
ii. Vertical load strength
iii. Resistance to impact
iv. Resistance to scratches and abrasions.
8. Mechanical strength of a bottle or jar can increase with glass weight.
a) True
b) False
Answer: a
Clarification: The given statement is true. Although the mechanical strength of a bottle or jar can increase with glass weight, this is at the expense of thermal strength which decreases with increasing glass weight. Considerable expertise is required by the glassmaker to determine the most appropriate design to satisfy the mechanical strength requirements and to balance the thermal strength demands of the finished product.
9. Glass has the most resistance to temperature changes relative to other packaging materials.
a) True
b) False
Answer: b
Clarification: The given statement is false. Relative to other forms of food packaging, glass has the least resistance to temperature changes. The resistance to thermal failure depends on the type of glass employed, the shape of the container and the wall thickness. When a glass container is suddenly cooled, tensile stresses are set up on the outer surfaces, with compensating compressional stresses on the inner surface. Conversely, sudden heating leads to surface compression and internal tension.
10. Glass loses its ability to transmit light on irradiation.
a) True
b) False
Answer: True
Clarification: The given statement is true. Glasses and other transparent materials tend to darken and lose much of their ability to transmit light when bombarded by high energy radiations such as those used in food irradiation. There are two principal causes of this coloration of glass. First, the displacement of electrons can create holes which could lead to formation of color centers. Second, changes in the valence shell of metal oxides can result in increased absorption of light in the visible wavelength.