11.

List two functions performed by the testis in human beings.

What is the function of ozone in the upper atmosphere?

List four characteristics of the images formed by plane mirrors.

Why are forest considered biodiversity hot spots? List two ways in which an individual can contribute effectively to the management of forests and wildlife.

What is meant by 'sustainable management'? Why is reuse considered better than recycling?

With the help of an example, explain the process of hydrogenation. Mention the essential conditions for the reaction and state the change in physical property with the formation of the product.

What is the difference between the molecules of soaps and detergents, chemically? Explain the cleansing action of soaps.

How many groups and periods are there in the modern periodic table? How do the atomic size and metallic character of elements vary as we move:

(a) Down a group and

(b) From left to right in a period

From the following elements:

₄Be; ₉F; ₁₉K; ₂₀Ca

(i) Select the element having one electron is the outermost shell.

(ii) two elements of the same group.

Write the formula and mention the nature of the compound formed by the union of ₁₉K and element X(2, 8, 7).

What is DNA copying? State its importance.