Lecture 03 Properties of H20, Hydrogen Bonds, Acids and Bases

Water

A vital substance for life, constituting 55-60% of human body mass and essential for biochemical reactions.

Biochemical Reactions

Chemical processes that occur within living organisms, requiring an aqueous environment.

Temperature Buffer

Water's ability to resist temperature changes, stabilizing organisms and ecosystems.

- requires 1 gram of heat to change 1 degree

-polar substances more likely to form hydrogen bonds( increases specific heat)

Covalent Bonds

Chemical bonds formed by the sharing of electrons between atoms, as seen in water molecules.

Electronegativity

The tendency of an atom to attract electrons; oxygen is more electronegative than hydrogen in water.

Polar Covalent Bonds

Bonds in which electrons are shared unequally, resulting in partial charges; characteristic of water.

Polar Molecule

A molecule with a net dipole moment due to the presence of polar bonds; water is a polar molecule.

Hydrogen Bonds

Weak attractions between a partially positive hydrogen atom and a partially negative atom, allowing water to remain liquid at room temperature.

-one water molecule can form 4 hydrogen bonds

-only hydrogen can form bonds with oxygen

Liquid Water

Water in its liquid state, capable of forming four hydrogen bonds per molecule.

Methane

A nonpolar molecule that cannot form hydrogen bonds, resulting in it being a gas at room temperature.

Polarity

The distribution of electrical charge over the atoms in a molecule, affecting solubility in water.

Hydrophilic

Describes polar molecules that are soluble in water; "water-loving."

Hydrophobic

Describes nonpolar molecules that are insoluble in water; "water-fearing."

-water can influence the shape of non-polar molecules shape/structures

-non polar molecules do not form hydrogen bonds

Acids

Substances that donate protons (H+) in a chemical reaction, according to the Brönsted-Lowry definition.

-lower value( under 7)

Bases

Substances that accept protons (H+) in a chemical reaction, according to the Brönsted-Lowry definition.

-higher value( above 7)

-combines with hydrogen to balance charges

pH Scale

A logarithmic scale that measures the acidity or basicity of a solution, defined as the negative log of H+ concentration.

• 10 fold( scale from -1 to -14

Neutral pH

A pH of 7.0, where the concentration of hydrogen ions [H+] equals the concentration of hydroxide ions [OH-].

Acidic pH

A pH less than 7.0, where [H+] is greater than [OH-].

Basic pH

A pH greater than 7.0, where [H+] is less than [OH-].

Water is polar/ influence on shape

-covalent bond that is unequal

-try to form maximize amount of hydrogen bonds

- it will surround substances with electrical charge preventing others from reaching it

- hydrophilic

What determines if molecule can hydrogen bond

-nonpolar molecules cannot hydrogen bond

-reference EN

-less than 0.5