Why is the path of light not visible in a solution when a beam of light is passed through it?

What are metalloids? Give examples.

Which of the tubes in Fig. $(a)$ and $(b)$ will be more effective as a condenser in the distillation apparatus?

$(a)$ $7\, g$ of iron filings and $4\, g$ of sulphur powder is treated with dilute sulphuric acid at room temperature. Name the gas produced.
$(b)$ The same mixture is heated strongly,cooled and then treated with dilute sulphuric acid. Which gas would be produced?
$(c)$ What is the cause of this difference in results of chemical reaction in different conditions?

$A$ mixture containing two liquids visibly separated,is placed in a separating funnel. Answer the following:
$(i)$ What type of liquids form the mixture?
$(ii)$ Which of the liquids will form the lower layer?
$(iii)$ What is the principle behind this method of separation?

Suggest separation technique$(s)$ one would need to employ to separate the following mixtures:
$(a)$ Mercury and water
$(b)$ Potassium chloride and ammonium chloride
$(c)$ Common salt,water and sand
$(d)$ Kerosene oil,water and salt