Final answer:
The correct order of substances by increasing polarity is CH4, CS2, NH3, and KBr, based on their molecular structures and electronegativity differences.
Step-by-step explanation:
To arrange the substances CH4, CS2, KBr, and NH3 in order of increasing polarity, we must consider the electronegativities of the atoms and the molecular structure of the compounds. Methane (CH4) is a nonpolar molecule with equal sharing of electrons between carbon and hydrogen atoms. Carbon disulfide (CS2) is a linear molecule with polar bonds but the overall molecule is nonpolar due to the symmetrical arrangement cancelling the bond polarities. Ammonia (NH3) is a polar molecule due to its trigonal pyramidal shape causing an uneven distribution of charge. Potassium bromide (KBr) is an ionic compound with a high polarity as it is formed by transfer of electrons from potassium to bromine. Hence, in order of increasing polarity, the correct arrangement is: CH4 < CS2 < NH3 < KBr.