Which of the statements about glass are correct ? 1. Glass is a super-cooled liquid having infinite viscosity 2. Violet coloured glass is obtained by adding Mn02 3. Glass is a man made silicate 4. Glass is a crystalline substance Select the correct answer

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Q: 39 (NDA-I/2011)

Which of the statements about glass are correct ?
1. Glass is a super-cooled liquid having infinite viscosity
2. Violet coloured glass is obtained by adding Mn02
3. Glass is a man made silicate
4. Glass is a crystalline substance
Select the correct answer using the code given below :

question_subject: 

Science

question_exam: 

NDA-I

stats: 

0,14,45,17,17,14,11

keywords: 

{'glass': [0, 0, 1, 4], 'coloured glass': [0, 0, 0, 1], 'crystalline substance': [0, 0, 0, 1], 'silicate': [0, 0, 0, 1], 'mn02': [0, 0, 0, 1], 'infinite viscosity': [0, 0, 0, 1], 'violet': [2, 1, 3, 3]}

Option 1 states that glass is a super-cooled liquid with infinite viscosity. This statement is incorrect. Although there is a common misconception that glass is a super-cooled liquid, it is actually an amorphous solid.

Option 2 states that violet-colored glass is obtained by adding Mn02. This statement is correct. Manganese dioxide (MnO2) is commonly used as a colorant in glass manufacturing processes to achieve violet or purple hues.

Option 3 states that glass is a man-made silicate. This statement is correct. Glass is primarily made from silica, which is a natural compound found in abundance in the Earth`s crust. Silicate compounds are formed by combining silica with various other elements.

Option 4 states that glass is a crystalline substance. This statement is incorrect. Unlike crystalline substances, glass does not have a regular, repeating atomic structure. Instead, it has a disordered, amorphous structure.

In summary, the correct statements about glass are 2, 3, and 4.