BIOL-L112 Chapter 3

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polarity of water makes it a versatile solvent bc

it forms hydrogen bonds easily

hydrogen bonding is responsible for

water's high specific heat

3 things that help explain why water molecules form hydrogen bonds

1. Attractions form between opposite partial charges 2. There is a partial positive charge on each hydrogen atom and two partial negative charges on the oxygen atom in a water molecule 3. The electrons spend more time around the oxygen atom because oxygen is more electronegative than hydrogen

4 emergent properties of water

1. cohesive behavior 2. ability to moderate temperature 3. expansion upon freezing 4. versatility as a solvent

In the molecule below, how many atoms could make hydrogen bonds with water?

10

___% less dense than liquid water at 4C

10

concentration of H+ and OH- in pure water:

10^-7 each at 25C

what is the max number of hydrogen bonds one molecule of water can form?

4

each molecule of water is bound to

4 neighboring water molecules in a fixed structure

How many atoms in the pictured molecule can form hydrogen bonds with water molecules?

5

most cells are surrounded by water and cells themselves are about _______ water

70-95%

Why isn't this insect drowning?

Surface tension.

alkalosis:

pH of blood is greater than 7.45

acidosis:

pH of blood is less than 7.35

The unequal sharing of electrons within a water molecule makes the water molecule _____.

polar

is ammonia (NH3) a polar or nonpolar molecule?

polar

water is a highly ____ molecule

polar

In this molecule, what type of bond is found between the oxygen and hydrogens?

polar covalent

In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by _____.

polar covalent bonds

electronegativity

the attraction of an atom for the electrons in a covalent bond

changes in concentrations of H+ and OH- can drastically affect

the chemistry of the cell

adhesion:

the clinging of one substance to another

cohesion:

the clinging of one substance to itself

The partial negative charge in a molecule of water occurs because _____.

the electrons shared between the oxygen and hydrogen atoms spend more time around the oxygen atom nucleus than around the hydrogen atom nucleus

temperature:

the measure of energy that represents the average kinetic energy of molecules

water's cohesive and adhesive properties enable

the transport of water & dissolved nutrients upwards in plants against the force of gravity

measure temperature directly with a _____

thermometer

why do He, Ne, and Ar have no electronegativity value?

they have a full outer shell

why are water's emergent properties important?

they help make earth an environment that is suitable for life

heat:

total amount of kinetic energy due to random motion of atoms or molecules in a body of matter

the attraction of an atom for the electrons in a covalent bond

two atoms that do not have similar electronegativities.

characteristics of polar molecules

unequal sharing of electrons, frequently asymmetrical, has partial positive and partial negative charges, electronegativity is 0.4-2

water has high heat of

vaporization

water absorbs heat from air that is

warmer

ion and polar regions on the protein's surface attract

water molecules

at equilibrium, _________ water molecules is dissociated

1 out of 554,000,000

to increase temp of water:

1) average kinetic energy of water must increase 2) heat absorbed must be enough to break the hydrogen bonds and increase the molecule's kinetic energy

units of temperature

C,F,K

Right before a predicted overnight freeze, farmers spray water on crops to protect the plants. Use the properties of water to explain how this method works. Be sure to identify why hydrogen bonds are responsible for this phenomenon.

Due to intermolecular hydrogen bonds, water has high specific heat. When water is cooled, many of these bonds are formed, which releases a significant amount of heat. This can provide some protection against freezing of the plants' leaves, thus protecting the cells from damage.

Nitrogen (N) is more electronegative than hydrogen (H). Which of the following is a correct statement about the atoms in ammonia (NH3)?

Each hydrogen atom has a partial positive charge; the nitrogen atom has a partial negative charge.

which element is the most electronegative?

F

The partial negative charge at one end of a water molecule is attracted to the partial positive charge of another water molecule. What is this attraction called?

a hydrogen bond

aqueous solution:

a solution in which water is the solvent

water exists in the natural environment in:

all 3 physical states

why is it important that life floats?

allows life to exist under frozen surfaces

specific heat:

amount of heat absorbed or lost when 1g of a substance changes its temp by 1C

heat of vaporization:

amount of heat needed to convert 1g of liquid to gaseous state

units of heat

calorie- amount of heat it takes to raise the temp of 1g water 1C

Hydrogen bonds ...

can form between H and N.

Which property of water is responsible for the formation of raindrops?

cohesion property

Water molecules can form hydrogen bonds with _____.

compounds that have polar covalent bonds

water releases heat to air that is

cooler

an increase in pH means that the concentration of H+ has

decreased

solvent:

dissolving agent of a solution (water)

The tendency of an atom to pull electrons toward itself is referred to as its _____.

electronegativity

characteristics of nonpolar molecules

equal sharing of electrons, usually symmetrical, have little or no partial charges, electronegativity is 0-0.4

water's high heat of vaporization leads to

evaporate cooling

Polar attractions are ...

forces between atoms with partial charges, weaker than covalent bonds, important because they are numerous.

A water molecule can bond to up to _____ other water molecules by ____ bonds.

four; hydrogen

when in liquid form, hydrogen bonds are

fragile and short lived

hottest molecules are most likely to leave as

gas, leaving behind cooler molecules

the faster a molecule moves, the ______ its kinetic energy

greater

liquid water is at its

greatest density at 4C

The brackets are indicating a(n) _____ bond.

hydrogen

What name is given to the bond between water molecules?

hydrogen

polarity enables water to form

hydrogen bonds

floating ice _____

insulates liquid below

water's ability to moderate temp stems from ___

its high specific heat

anything that moves has

kinetic energy

atoms and molecules have

kinetic motion

solution:

liquid that is a completely homogenous mixture of 2 or more substances

heat does depend on _____

matter's volume

temperature does not depend on _____

matter's volume

adding acids and bases will

modify the concentrations of H+ and OH- of a solution

the lower the pH of a solution, the __

more acidic the solution

a calorie of heat causes a relatively small change in temp bc

much of the heat is used to break hydrogen bonds before the molecules can move faster

can heat be measured with a device directly?

no

does a partially negative charged oxygen atom have to be present in a hydrogen bond?

no

water can also dissolve compounds made of

nonionic polar molecules

is oxygen (O2) a polar or nonpolar molecule?

nonpolar

Bonds between two atoms that are equally electronegative are _____.

nonpolar covalent bonds

Sulfur is in the same column of the periodic table as oxygen, but has electronegativity similar to carbon. Compared to water molecules, molecules of H2S will _____.

not form hydrogen bonds with each other

A covalent bond is likely to be polar when ________.

one of the atoms sharing electrons is more electronegative than the other atom

hydrophilic:

one that has affinity for water (NaCl, glucose, some proteins)

hydrophobic:

one that repels water (olive oil)

free H+ and OH- are ____

rare yet biologically important

when blood pH drops (acidosis):

reaction will proceed to left to maintain pH homeostasis. more H2CO3 forms and H+ decreases, pH increases

when blood pH increases (alkalosis):

reaction will proceed to right to maintain pH homeostasis. more H2CO3 dissociates and H+ increases, pH decreases

What type of bond joins the carbon atom to each of the hydrogen atoms?

single (nonpolar) covalent

Rubbing alcohol swab on the skin feels cool because ________.

skin transfers heat to the liquid alcohol and the alcohol evaporates

absorbs & releases large amounts of heat w _____ changes in temperature

slight

sugar dissolves when stirred in water. sugar is the

solute

sugar dissolves when stirred in water. sweetened water is the

solution

sugar dissolves when stirred in water. water is the

solvent

hydration shell:

sphere of water molecules that surrounds solutes when they are dissolved in water

acid:

substance that increases the H+ concentration of a solution

solute:

substance that is dissolved (NaCl)

buffers:

substance that keep in the pH of biological fluids relatively constant

base:

substance that reduces the H+ concentration of a solution

true statement pertaining to sweat:

sweating cools the body by converting water into gas

which has more heat: water in a lukewarm swimming pool or boiling water in a teacup?

swimming pool

which has the highest temperature: water in a lukewarm swimming pool or boiling water in a teacup?

teacup

does a partially positive charged hydrogen atom have to be present in a hydrogen bond?

yes


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