Question

1. what makes water so unique?
2. why is water called a universal solvent?
3. what does it mean to have a ph of 7?

Explanation:

1. Water is unique because it has a high specific heat capacity (absorbs/releases heat slowly), exists in three states (solid - ice, liquid - water, gas - water vapor) at Earth's normal temperatures, and has strong hydrogen bonding which gives it properties like high surface tension.
2. Water is called a 'universal solvent' because it can dissolve a wide variety of substances. Its polar nature (has a slightly positive and slightly negative end) allows it to interact with many ionic (e.g., salts) and polar covalent (e.g., sugars) compounds, surrounding and separating their particles.
3. A pH of '7' means the solution is neutral. On the pH scale (ranging from 0 - 14), pH 7 indicates that the concentration of hydrogen ions ($H^{+}$) is equal to the concentration of hydroxide ions ($OH^{-}$) in an aqueous solution.

Answer:

1. Water is unique due to its high specific heat capacity, existence in three states at normal Earth temperatures, and strong hydrogen - bonding properties.
2. Water is called a 'universal solvent' as it can dissolve many ionic and polar covalent substances because of its polar nature.
3. A pH of '7' means the solution is neutral (equal $H^{+}$ and $OH^{-}$ concentrations).