In the context of reproduction of species state the main difference between fission and fragmentation. Also give one example of each.

On dropping a small piece of sodium in a test tube containing carbon compound 'X' with molecular formula C₂H₆O, a brisk effervescence is observed and a gas 'Y' is produced. On bringing a burning splinter at the mouth of the test tube the gas evolved burns with a pop sound. Identify 'X' and 'Y'. Also write the chemical equation for the reaction. Write the name ind structure of the product formed, when you heat 'X' with excess cone. Sulphur acid.

Three elements 'X', 'Y' and 'Z' have atomic numbers 7, 8 and 9 respectively.

(a) State their positions (Group number and period number both) in the Modern Periodic Table.

(b)Arrange these elements in the decreasing order of their atomic radii.

(c) Write the formula of the compound formed when 'X' combines with 'Z'.

With the help of an example justify the following statement:

"A trait may be inherited, but may not be expressed."

The image of an object formed by a lens is of magnification -1. If the distance between the object and its image is 60 cm, what is the focal length of the lens? If the object is moved 20 cm towards the lens, where would the image be formed? State reason and also draw a ray diagram in support of your answer.