Biology Exam: Polarity, hydrogen bonds, and properties of water

Why is the density of ice important?

-Ice forming at the top of a body of water provides insulation because of the density of it -this is important because the isolation allows organisms to live in the water and not die off

Why do we care about chemistry in biology class?

-biology involves studying structures and functions -levels of organization: molecules to biosphere -molecules made of atoms - arrangement determines properties

Temperature moderation

-water can absorb a large amount of heat (ex. sunlight) with only a slight change in temperature -this prevents bodies of water like oceans or lakes, and our own bodies, from overheating on a hot day

why is it important to learn about water

-water makes life on earth possible -H20 covers more than 75% of earths surface -70-95% of an organisms mass is water -72% of the human body is water

Adhesion and capillary action

Adhesion between water molecules and for example glass molecules, will cause water to rise in a glass graduated cylinder, therefore playing a role in capillary action

Adhesion

An attraction between molecules of different substances. -responsible for capillary action

Cohesion

An attraction between molecules of the same substance -responsible for surface tension

How do H-bonds allow for cohesion?

Bonds between hydrogen allow for cohesion because it is an attraction between two hydrogen bonds, which are the same substance.

cohesion and capillary action

During capillary action, hydrogen bonds form between water molecules and cohesion occurs.

How does water dissolve ionic compounds?

Example: salt (NaCl) dissolving in water When water dissolves salt, the oxygen ion, which is slightly negative, of the water molecule is attracted to the slightly more positive sodium ion. Water molecules form a sphere of hydration around the sodium ion effectively separating it from chloride ion, breaking the NaCl down into its two ion forms. The same thing happens with the chlorides, all of the slightly more positive hydrogen ends of the water molecule attract to the negative chlorine, effectively separating it from the sodium ion.

H-bonds and adhesion

Hydrogen bonds are responsible for waters adhesiveness Bonds between hydrogen and a non-water substance allows for adhesion because it is an attraction between H-bonds and molecules of a different substance

H-bonds and temperature moderation

In water, molecules are moving fairly quickly. In gaseous water, or steam, molecules are moving much faster. Because H molecules are moving a little bit slower in liquid, the have more time to form hydrogen bonds. If liquid water was exposed to an energy source like the sun, a ton of that energy goes into breaking the bonds instead of heating up the water, which is why is takes lots of energy to heat up water.

Density of water in solid vs. liquid water

Most of the time, solids are denser than liquids, however water's an exception. Ice is less dense than liquid water, which causes ice to float in liquid water.

What does not dissolve in water?

Since water is polar, water does not dissolve non-polar substances. like oil. For example: salad dressing because it is mainly oil based

What 6 elements make up 99% of living matter?

Sulfur Phosphorus Oxygen Nitrogen Carbon Hydrogen **remember sponch

Surface tension

Surface tension is due to cohesion. Hydrogen bonds form between water molecules (cohesion) at the surface causes there to be a dome-like shape to the water and causes a down-like pull, preventing in the water from spilling over (to a point) example: filling a glass over the brim a little bit and it not spilling over

Water as a universal solvent?

Water can dissolve many substances because it's polar like ionic compounds and other polar substances -"like dissolves like" = solvents or liquids that dissolve other things can dissolve things that are similar to them -because water is polar, it can dissolve other things that are polar - water has a neutral pH:7 (neither an acid or a base)

capillary action

adhesion between molecules that results in the rise of the surface of a liquid when it comes in contact with a solid

what is a polar molecule

an uneven distribution of electrons between atoms within one molecule

element

cannot be chemically broken down into something simpler -118 elements are known -92 elements occur in nature -25 elements are essential for life

Why is water

idk you tell me

Electrons

negative outside nucleus, found in energy levels e-

H-bonds in the density of solid vs. liquid water

nevermind the pic isnt coming

neutrons

no charge found in the nucleus n0

protons

positive in the nucleus p+

what is a hydrogen bond?

the attraction between the positive hydrogen atom on one water molecule and negative oxygen atom on another water molecule

all atoms have

the same general arrangement

atom

the smallest particle of an element that still retains the properties of that element

Water can be neutral and still be a polar molecule?

yes, water is a polar molecule because the electrons between hydrogen and oxygen are shared unevenly -a water molecule itself is neutral (10 total protons and 10 total electrons)