Biology Ch. 3

• 2 ends of molecule have opposite charges.
• Ex. Water molecule have unequal distributions of electrons. Oxygen electronegativity is partially negative and Hydrogen is partially positive

• Hydrogen Bonds hold the substance together.
• HENCE: water is linked by many hydrogen bonds that make it more structured than any other liquid.
• Cohesion (due to Hydrogen Bonding): contributes to transport of water & dissolved nutrients against gravity.

• Clinging of one substance to another
• Ex. Adhesion of water to cell walls by hydrogen bonds help counter the downward pull of gravity.
• Fig. 3.3

• Measures how difficult it is to break or stretch the surface of liquid.
• (related to cohesion)
• *Water has the greatest surface tensions of liquids

• Energy of motion. Anything that moves has Kinetic Energy.
• Ex. Atoms and molecules have K.E. b-kuz they are always moving. The faster = higher kinetic energy

• is a form of energy. Heat is the measure of the matter's TOTAL kinetic energy due to motion of its molecules. THUS it depends on its VOLUME.
• Ex. A coffee mug's temperature is higher but if the swimming pool temperature isn't as hot, swimming pool has a higher amount of HEAT due to volume.

Measure of heat intensity that represents the average kinetic energy of molecules, regardless of volume.

To indicate temperature. Water freezes: 0 Degree C and Boils: 100 Deg. C

A unit of heat, and a calorie = to raise 1 gram of H₂O by 1^.C

• =1000 calories, it takes 1 kilocalorie to raise 1 kilogram of H₂O by 1' C.
• Calorie on food packages are actually kilocalories.

The amount of heat a 1 gram substance must absorb or lost to change the temperature to 1^'C

quantity of heat a liquid must absorb for 1 gram of liquid to convert into gaseous state.

a liquid that is a completely homogenous mixture of two substances.

• dissolving agent of a solution.
• Ex. Water is the solvent and sugar is the solute.

A substance that is being dissolved.

is when water is the solvent.

• A substance that has an affinity for water.
• Some substances are hydrophilic without dissolving
• Ex. Molecules that are so large and can't dissolve & remain suspended in the aqueous liquid of the cell. A mixture called colloid.
• Ex. 2 Cotton does not dissolve and it consists of giant molecules of cellulose, which contains partial positive and negative charges, that aid in hydrogen bonding. Water adheres to cellulose fibers.

• No affinity for water, nonionic or nonpolar (or for some other reason that cannot form hydrogen bonds) repel water.
• Ex. Oil (hydrophic behavior) result from prevalence of nonpolar bonds, such as Hydrogen and Carbon, which share their electrons equally (don't dissolve in oil). Cell membranes share similar qualities (hydrophobic molecules) because cell membranes can't be dissolved!)

Measuring molecules is not practical, so measure substances in Moles. Moles = 6.02 x 10²³. There are 6.02 x 10²³ daltons in 1g.

Sum of all the masses of the atom

is equal to the number of moles of solute per liter of solution. mol/1000 mL or L

• H⁺, a single proton with a positive charge.
• (Occasionally hydrogen atoms participate in hydrogen bonds, leaves electron behind and and transfers hydrogen ion (H⁺)

(OH^_) Molecule that lost an Ion, has a negative charge.

• Substance that increases the H⁺ (hydrogen ions) concentration of a solution.
• Ex. When hydrochloric acid (HCl), hydrogen ions dissociate from chloride Ions (HCl ---> H⁺ + Cl^-
• This source of H⁺ (dissociation of water is the other source) results in an acidic solution - one having more H⁺ than OH^-.

• BASE: (More OH^-) is a substance that reduces the hydrogen ion (H⁺) concentration of a solution.
• (Some base reduce hydrogen ion concentration by accepting H⁺ directly. NH₃ + H⁺ ---> NH⁴ (ammonia becomes ammonium ion) or dissociates to give a higher OH^- Solution. NaOH ----> Na⁺ OH^-

• pH = to -log [H⁺] (-log 10^-7 = -(-7) = 7. pH goes down as H+ concentration increases.
• A solution of pH 10 has a hydrogen ion concentration of 10^-10M so hydroxide concentration will be 10^-4 M. (H⁺ and OH^- always have to equal to 10^-14)

• are substances that minimize the changes in the concentration of H⁺ and OH^- in a solution.
• (why?) So pH of living cells do not fluctuate too much. Buffers do so by accepting hydrogen ions from the solution when they are in excess and donating hydrogen ions when they are depleted.

refers to rain, snow, or fog with a pH lower than 5.2 (more acidic). Burning fossil fuels make sulfur oxides and nitrous oxides, then these react with water in the air to form strong acids, which fall to earth in rain or snow.