Chapter Three: Water & The Fitness of the Environment Flashcards
What is a polar molecule? What is its relation with the properties of water?
A molecule with opposite charges on different ends of the molecule. It is the reason for water’s properties.
What causes water to be fragile in liquid form? What are its four emergent properties?
Water is constantly re-forming hydrogen bonds with its neighbors. It hydrogen bonds to multiple partners (positive and negative parts attract). Four emergent properties are cohesion, moderation of temperature, expansion upon freezing, and it is the solvent of life.
Cohesion v.s. Adhesion
Cohesion is the binding together of like molecules, often by hydrogen bonds. It contributes to the transport of water & dissolved nutrients against gravity in plants. Adhesion is the clinging of one substance to another. It helps counter the downward pull of gravity.
Definition of Surface Tension
A measure of how difficult it is to stretch or break the surface of a liquid. Water has a great surface tension.
How can water moderate air temperature?
Water can moderate air temperature by absorbing heat from warmer air, & releasing it to cooler air. It absorbs/releases lots of heat with a light change in its temperature (it acts as a heat bank).
What is kinetic energy? What is the difference between heat and temperature? What is the Celsius scale?
Kinetic energy is the energy of motion.
Heat is a form of energy; it is a measure of matter’s total kinetic energy and depends on the matter’s volume.
Temperature is a measure of heat intensity that represents the average kinetic energy of the molecules (no volume needed!). The Celsius scale is a temperature scale that measures the freezing & boiling point of water.
Calorie v.s. kilocalorie v.s joule
Calorie: the amount of heat it takes to raise the temperature of 1 gram of water by 1 degree C.
Kilocalorie: the amount of heat required to raise the temperature of 1 kilogram of water by 1 degree C; 1 kcal = 1,000 cal
Joule: a unit of energy; 1 cal: 4.184 J 1 J = 0.239 cal
What is specific heat?
Specific heat is the amount of heat that must be absorbed or lost for one gram of that substance to change its temperature by 1 degree C. Water has a high specific heat of 1 cal/g/C. When heat is released, hydrogen bonds form, when heat is absorbed, hydrogen bonds break. It keeps temperature fluctuations on land and in water within limits that permit life; organisms can resist changes in their temperature.
Definition of heat of vaporization
The quantity of heat a liquid must absorb for one gram of it to be converted from liquid to gas. Hydrogen bonds must be broken to get to a gas.
Definition of Evaporative Cooling
The process where an object becomes cooler during evaporation, owing to a change of the molecules with the greatest kinetic energy from liquid to gas. It proves stability of temperature in water and a mechanism that prevents terrestrial organisms from overheating.
How does water expand instead of contracting when it solidifies?
Water is less dense as a solid than as a liquid. It begins to freeze when its molecules are no longer moving vigorously enough to break their hydrogen bonds. Its greatest density is at 4 degrees C. Hydrogen bonds are stable.
What is the difference between a solution and an aqueous solution? Solvent v.s. Solute
Solution: a liquid that’s completely homogeneous mixture of at least two substances.
Aqueous solution: a solution where water is the solute
Solute: thing that’s dissolved
Solvent: dissolving agent
Definition of hydration shell and colloid
the sphere of water molecules around a dissolved ion. Compounds both ionic and nonionic can dissolve in water
Colloid: a stable suspension of fine particles in a liquid
Hydrophillic vs. hydrophobic
Hydrophillic: Any substance that’s attracted to water; some can’t dissolve
Hydrophobic: nonionic/nonpolar substances unable to form hydrogen bonds and repels water
Definition of molecular mass
the sum of the masses of all the atoms in a molecule