Ch 2: Water and Life

Question 1

Define a Polar molecule?

Answer 1

A molecule that has unequal sharing of electrons due to one atom being more electronegative than the other.

Question 2

Why is water considered polar?

Answer 2

Water is polar because the oxygen atom is more electronegative than the hydrogens, thus making it so that oxygen has electrons closer to it.

Question 3

What is hydrogen bonding?

Answer 3

Hydrogen bonding is where the partial negative charge of oxygen attracts to the partial positive region of hydrogen from another molecule. Not from the same molecule, those are polar covalent bonds

Question 4

How many hydrogen bonds can a single water molecule form?

Answer 4

4

Question 5

Distinguish between cohesion and adhesion.

Answer 5

cohesion is where water molecules stick to other water molecules, adhesion is from a water molecule to a nonwater polar molecule

Question 6

Which is demonstrated when you see beads of water on a waxed car hood?

Answer 6

adhesion because water is sticking to a nonwater molecule and maybe cohesion because beads of water

Question 7

Water has high specific heat. What does this mean?

Answer 7

This means water can resist change in temperature/it absorbs more heat before 1g of it raises by 1C.

Question 8

How does water’s specific heat compare to alcohol’s specific heat?

Answer 8

Water has higher specific heat than alcohol.

Question 9

Explain how hydrogen bonding contributes to water’s high specific heat.

Answer 9

Hydrogen bonds absorb a ton of energy compared to other bonds in order to break which slightly increases the temperature

Question 10

Summarize how water’s high specific heat contributes to the moderation of temperature. How is this property important to live?

Answer 10

Due to water’s high specific heat, water/hydrogen bonds are able to absorb large amounts of heat from hotter areas until they break, and redistribute them into colder areas reforming. This moderates the temperature. This is important to live because water-based organisms can take more heat.

Question 11

Define evaporation

Answer 11

When atoms in a liquid move rapidly until they break apart and become a gas.

Question 12

What is the heat of vaporization?

Answer 12

The heat needed to make 1g of that liquid into gas, water has a high heat of vaporization

Question 13

Explain at least three effects of the evaporation property on living organisms.

Answer 13

1. evaporation is need for the water cycle
2. water’s high heat of vaporization makes it so organisms composed of water are not simply turned into a gas
3. evaporation is also needed for water to be transported in plants

Question 14

What would happen if ice did not float.

Answer 14

If ice did not float then all bodies of water would simply be filled with ice since the ice will accumulate towards the bottom and will make not only marine life impossible but also human life.

Question 15

Now, explain why ice floats

Answer 15

Ice floats because it is less dense than the water around it

Question 16

Why is 4°C the critical temperature?

Answer 16

at this temperature, hydrogen bonds start to slowly break and space out all the water molecules, this is when water reaches its greatest density.

Question 17

Explain why water is such a fine solvent.

Answer 17

water is a good solvent because any ionic or polar substance placed in water will dissolve

Question 18

Distinguish between hydrophobic and hydrophilic substances. Give an example of each.

Answer 18

hydrophobic means it can not dissolve in water, this consists of fats oils, or anything nonpolar. Hydrophilic is where anything ionic or polar can dissolve in water, this includes sugars.

Question 19

Oil will float on top of water. Explain this property in terms of hydrogen bonding.

Answer 19

Since oils are nonpolar they will repel away without making any hydrogen bonds with water.

Question 20

What two ions form when water dissociates?

Answer 20

OH- or hydroxide ion and H+ or hydrogen ion

Question 21

Even a slight change in pH can be harmful! How do buffers moderate pH change?

Answer 21

buffers like carbonic acid can receive H+ and redistribute it in places that lack H+

Question 22

Exercise will result in the production of CO2, which will acidify the blood. Explain the buffering system that minimizes blood pH changes.

Answer 22

judging by the name, the buffering system could use buffers like carbonic acid in order to regulate pH changes in blood

Question 23

Discuss how CO2 emissions affect marine life and ecosystems.

Answer 23

As we know CO2 can make the ocean more acidic, and slight changes in pH are very dangerous. It can hurt marine life and even destroy some ecosystems.

Question 24

define surface tension, and water’s surface tention

Answer 24

surface tension is how tough it is to stretch or break the surface of a liquid. Water uses cohesion to attach to other water molecules in order to create some kind of barrier at the surface. Water’s asymmetry gives water strong surface tension.

Question 25

solution

Answer 25

a mixture of 2 or more substances

Question 26

solvent

Answer 26

dissolves the other substance

Question 27

solute

Answer 27

the one being dissolved

Question 28

hydration shell

Answer 28

water forms around atoms of the solute and separate the molecules from each other.

Question 29

acid

Answer 29

adds more H+ by dissolving into a solution

Question 30

base

Answer 30

decreases H+ by accepting more H+

Question 31

name water’s 4 emergent properties

Answer 31

4 emergent properties of water: cohesion, moderation of temperature, expansion upon freezing, and versatility as a solvent

Question 32

What happens when hydrogen bonds are formed and broken

Answer 32

heat is absorbed when broken and heat is released when made.

Question 33

evaporative cooling

Answer 33

As a liquid evaporates, its remaining surface cools. This helps stabilize temperatures.

Question 34

how often do water molecules break and reform

Answer 34

almost every one trillionth of a second

Question 35

What is the neutral temp for pH

Answer 35

25C 10^-7 for both

Question 36

What is a more basic and acidic solution

Answer 36

a basic solution is when OH- is more than H+

Question 37

alkaline

Answer 37

a lot of hydroxide ion

Question 38

pH scale

Answer 38

1 to 14, increases 10 fold, remember the increase in pH is a decrease in acidity and H+