Water: Polarity, Solvent Properties, and Heat Capacity

Flashcards covering water's polarity and hydrogen bonding, solvent properties (polar vs nonpolar), dissolution, ion hydration, and the heat capacity and temperature-stabilizing role of water as described in the notes.

What structural feature gives water its polarity and enables hydrogen bonding with other water molecules?

A bent geometry with a dipole moment (approximately 104.5°) that allows hydrogen bonds between molecules.

What type of bonds form between adjacent water molecules?

Hydrogen bonds.

Water acts as the universal solvent for which type of molecules, and which type does it not dissolve?

It dissolves polar molecules and cannot dissolve nonpolar molecules (e.g., soap is nonpolar).

Why are chemical reactions in cells typically occurring in an aqueous environment, and what is the role of water for enzymes?

Because reactions occur in water; enzymes require the presence of water to function in an aqueous environment.

What happens when NaCl dissolves in water in terms of species present?

NaCl dissociates into Na+(aq) and Cl−(aq) ions solvated by water.

Is water a stoichiometric reactant in dissolution reactions?

No. Water acts as a solvent and is not consumed in the dissolution process.

How do water molecules interact with ions like Na+ and Cl− in solution?

Water molecules form hydration shells around ions via ion-dipole interactions.

How is heat capacity defined, and how does it differ from specific heat?

Heat capacity is the energy required to change a substance's temperature; specific heat is the heat required per gram per degree Celsius.

What is the specific heat of water?

1 calorie per gram per degree Celsius (1 cal/g·°C).

Compared to gold, how much more energy can 1 kg of water store for the same temperature change?

About 30 times more calories; water has a much higher heat capacity than gold.

Why is water an effective temperature stabilizer for living organisms?

Its high specific heat capacity buffers temperature changes, helping maintain stable internal temperatures.

What percentage of the human body is water, and why is this significant for temperature regulation?

Approximately 70–95% water; this high water content aids in stabilizing body temperature.

Which property most explains why blood plasma can be maintained at a stable temperature?

High specific heat capacity, which buffers temperature changes.

In a heat-exchange example, which substance absorbs heat more slowly, water or gold, and what does this illustrate?

Water absorbs heat more slowly due to its higher heat capacity, illustrating its greater heat storage capability.

What does the statement 'water is not a stoichiometric reactant' imply in chemical reactions?

Water is a solvent and is not consumed in the stoichiometry of the reaction.