The milkman in our society started carrying a lactometer. His move was well appreciated by the society members.
$(a)$ What is the use of a lactometer? On what principle does it work?
$(b)$ What values of the milkman are shown by this move?

Chemical formula of a compound is a symbolic representation of its composition. We should know the following points to write the chemical formulae of chemical compounds:
$(i)$ Symbols of the combining elements.
$(ii)$ Valency of the combining elements.
In order to know the valency,we must calculate the valence electrons present in the atoms.
The electrons present in the outermost shell or valence shell are called valence electrons. The number of electrons in the atoms of some elements are given below. The elements which have one valency are called monovalent.
$(a)$ What is a chemical formula?
$(b)$ Which main points we must know to write the chemical formula of compounds?
$(c)$ Which values do we find associated with the use of formula for various things in daily life?

$(a)$ State two differences between egg layers and broilers.
$(b)$ How can poultry fowl be prevented from various diseases? State any three methods.

$(a)$ Mention the harmful effects of infectious diseases on the health of cattle.
$(b)$ How can these diseases be controlled?

Differentiate between layers and broilers.

On what factors do the growth of plants and flowering depend?