1.3 Chemistry of Water

Question 1

Which one is NOT one of the properties of water?

water is a solvent

the frozen form is more dense than the liquid form

water has a high heat of evaporation

water has a high heat capacity

Answer 1

the frozen form is more dense than the liquid form

Question 2

If you place the corner of a paper towel into a droplet of water the water moves across the paper towel. Which of the following would explain the movement of the water?

surface tension

cohesion

adhesion

both cohesion and adhesion

Answer 2

both cohesion and adhesion.

Question 3

A coastal climate is moderated primarily by which of the following properties of water?

Water…

has a high heat of evaporation.

is the universal solvent.

has a high surface tension.

is cohesive and adhesive.

Answer 3

Water has a high heat of evaporation.

Question 4

Which term refers to the attraction to water molecules?

hydrophobic

hydrolysis

nitrophylic

hydrophilic

Answer 4

Hydrophilic.

Question 5

As a solid, water floats. This means that

this is due to oxygen bonding changes.

All of the choices are correct.

solid water is more dense than liquid water.

organisms in ponds, lakes, and reservoirs can survive under the ice cover.

Answer 5

Organisms in ponds, lakes, and reservoirs can survive under the ice cover.

Question 6

What allows H2O to form hydrogen bonds?

Answer 6

Its shape and polarity.

Question 7

What is a hydrogen bond?

Answer 7

A weak attractive force between a slightly positive H to a slightly negative atom in the vicinity. It can be between the same or different molecules.

Question 8

True or false: many H bonds together makes something relatively strong.

Answer 8

True.

Question 9

What is the role of H bonds in biological molecules?

Answer 9

The H bonds between and within biological molecules (such as proteins, dna, etc) help maintain proper structure and function.

Question 10

True or false: 1 H bond is stronger than both ionic and covalent bond.

Answer 10

False; 1 H bond is weaker than both ionic and covalent bonds.

Question 11

True or false: H bonding is unique to water.

Answer 11

False; another example is when they hold strands of DNA together.

Question 12

How is hydrogen bonding in water important?

Answer 12

Without H bonds, water would freeze at -100C and boil at -91C, making most of the water on Earth steam. With H bonds, water freezes at 0C and boils at 100C.

Question 13

What are the 5 important properties of water?

Answer 13

Water has a high heat capacity; water has a high heat of evaporation; water is a solvent; water molecules are cohesive and adhesive; frozen water (ice) is less dense than liquid water.

Question 14

Why is it important that water has a high heat capacity?

Answer 14

The many hydrogen bonds in water helps it heat and cool more slowly than other liquids, which allows organisms to maintain their temperatures and protects them from rapid temperature changes.

Question 15

Why is it important that water has a high heat of evaporation?

Answer 15

It allows animals in hotter environments to cool down more efficiently because the hydrogen bonds mean that they need to use more body heat before the water or sweat evaporates, cooling them down. This property also keeps temperatures along coasts moderate.

Question 16

Why is it important that water is a solvent?

Answer 16

Water’s polarity lets it facilitate chemical reactions inside and outside living systems.

Question 17

Why is it important that water molecules are cohesive and adhesive?

Answer 17

Water’s cohesion allows it to be liquid under the conditions of temperature and pressure present on Earth’s surface. Cohesion allows liquid water to flow freely while keeping water molecules from separating.

Water’s cohesion and adhesion help it transport nutrients and waste through vessels. Adhesion lets water molecules adhere to the vessel walls, and cohesion keeps the water together, allowing it to travel up vessels through capillary action that is vital in plants.

Question 18

What is cohesion?

Answer 18

Cohesion is the ability of water molecules cling to each other due to hydrogen bonds. A water molecule can form hydrogen bonds with at most 4 other water molecules.

Question 19

What is adhesion?

Answer 19

Adhesion is the ability of water molecules to cling to other polar surfaces because of its polarity.

Question 20

Why is it important that ice is less dense than liquid water?

Answer 20

Water molecules get closer together as they cool, and liquid water is most dense at 4C. But below 4C, the hydrogen bonds become more rigid and open, causing the water molecules to spread out. This is why water expands as it freezes at 0C. Because of this, it is less dense and floats on liquid water; this is important because it prevents bodies of water from freezing solid so organisms can live in them during the winter.