Chapter 3: Water and Its Properties

Molecular Formula: Water is composed of two hydrogen atoms and one oxygen atom ( $H_2O$ ).
Polarity: Water is a polar molecule. Oxygen is more electronegative than hydrogen, causing an unequal sharing of electrons.
Covalent Bonds: Formed by electron sharing within the molecule (intramolecular). Water features polar covalent bonds between oxygen and hydrogen.
Hydrogen Bonds: Intermolecular forces where the partially positive hydrogen of one water molecule is attracted to the partially negative oxygen of another.

Hydrophilic: "Water-loving" substances that dissolve readily in water, typically composed of ions or polar molecules (e.g., $NaCl$ ).
Hydrophobic: "Water-fearing" substances that are non-polar and insoluble in water (e.g., hydrocarbons, lipids, and vitamins $A$ , $D$ , $E$ , and $K$ ).

Cohesion: The tendency of similar water molecules to stick together via hydrogen bonding.
Adhesion: The tendency of water molecules to stick to different types of molecules, such as plant cell walls.
Surface Tension: An elastic-like effect at the surface of the liquid allowing insects like the water strider to walk on its surface.
High Specific Heat: The amount of heat required to change the temperature of $1\,g$ of a substance by $1\,^{\circ}C$ . This property allows organisms to maintain a constant internal temperature and stabilizes ocean environments.
Biological Importance: These properties facilitate capillary action (pulling water from roots to leaves) and transpiration (evaporative water loss in plants).

Question: How many atoms does a water molecule have?
Response: 3.
Question: Water molecule is a nonpolar molecule. (True/False)
Response: False.
Question: A property in which same molecules stick together is called?
Response: Cohesion.
Question: Transpiration is the loss of water from plants through evaporation. (True/False)
Response: True.