* Polarity: Water is a polar molecule, meaning it has a positive and negative end due to the uneven sharing of electrons. Potassium nitrate is also an ionic compound, meaning it dissolves into positively charged potassium ions (K⁺) and negatively charged nitrate ions (NO₃⁻). Polar molecules and ions interact strongly with each other, leading to solubility.
* Non-polarity: Carbon tetrachloride is a non-polar molecule. It doesn't have a significant positive or negative end. Non-polar molecules generally do not interact well with polar molecules like water.
In short: "Like dissolves like." Water, being polar, will dissolve polar compounds like potassium nitrate. Carbon tetrachloride, being non-polar, will not dissolve well in water.
