Which of the following substances is used in smoke screens?

Which element of group $14$ decomposes steam to form dioxide and dihydrogen gas?

Which one of the following statements about the zeolites is false?

Which of the following elements reacts with water?

Which non-metals have high melting and boiling points? State them.

What are allotropes? Sketch the structure of two allotropes of carbon namely diamond and graphite. What is the impact of structure on physical properties of two allotropes?