1.2. Properties of water

Question 1

properties caused by H-bonds

Answer 1

1. surface tension
2. capillarity
3. water being a good polar solvent

Question 2

surface tension

Answer 2

• the force that tends to decrease the surface of water
• due to cohesion
• exceptionally strong bonds between water mol. on the surface (pulled down-sum of forces)
• can be disturbed by other molecules (detergent) - no tense surface

Question 3

capillarity

Answer 3

• the ability of a liquid to “climb up” a narrow tube
• due to cohesion and adhesion
• adhesion to hydrophilic molecules of the tube, cohesion brings other H2O mol. up
• mass pulled down by gravity and pushed down by pressure

Question 4

How is capillarity important for life maintenance?

Answer 4

water containing minerals from the ground is transported through the xylem of the plant toward upper parts

Question 5

xylem

Answer 5

plant vessel that transports water with minerals

Question 6

water being a good polar solvent

Answer 6

• reactants in cell respiration and photosynthesis would not react if not dissolved first
• due to adhesion
• hydrophobic substances (fat, cholesterol, CO2, O2) not dissolved but transported through blood covered by proteins (lipids - hemoglobin)

Question 7

How is the fact that water is a good polar solvent important for life maintenance?

Answer 7

Glucose, amino acids, and NaCl are easily transported through blood. Cell respiration, and photosynthesis.

Question 8

Why does a paper clip float on water surface?

Answer 8

Because of surface tension of water which is caused by the cohesion of molecules caused by their polarity. And also because of the adhesion of water molecules to molecules of the paper clip.

Question 9

How does detergent break surface tension?

Answer 9

By increasing the surface area; the hydrophilic heads of the detergent molecules place themselves between loosely packed water molecules, adhering themselves to them and breaking their strong h-bonds.

Question 10

heat capacity

Answer 10

the amount of heat needed to raise the temperature of a subject (physical property)

Question 11

Why does water have high heat capacity?

Answer 11

Because much of the energy (heat) is used up to break H-bonds instead of increasing molecules’ kinetic energy and temperature with it.
Water’s movement is limited by hydrogen bonds; it is slow to gain and lose heat.

Question 12

Why is it important for life that water has high heat capacity?

Answer 12

• aquatic habitats are thermally more stable than terrestrial
• water buffers (prevents) drastic changes in body temperature (stabilization)
• higher body temperature = denaturation of proteins
• enzymatic and catalyzed chemical reactions in the body occur only within a specific temperature range

Question 13

buoyancy

Answer 13

the upward force on the object immersed in water (physical property)

Question 14

buoyancy for life

Answer 14

density (organism) = density (water), don’t have to spend much energy on floating (like the case with air)

Question 15

viscosity

Answer 15

the “stickiness” of liquid which determines how easily it can flow (physical property)

Question 16

what does viscosity depend on

Answer 16

the amount of intermolecular forces (how strongly the molecules stick to each other) - more forces=greater friction= greater viscosity

Question 17

viscosity for life

Answer 17

impacts the ease of movement through aquatic habitat (harder to move in salt, but easier to float)

Question 18

thermal conductivity

Answer 18

the measure of a material’s ability to move heat - determines how easily energy transfers through a material

Question 19

In less conductive materials…

Answer 19

…heat moves slowly. They are better at insulation and preventing heat loss.

Question 20

In more conductive materials…

Answer 20

…heat moves rapidly. They are better at absorbing and transferring heat.

Question 21

thermal conductivity for life

Answer 21

• negative: hypothermia in cold water - takes away body heat fast
• positive: thermoregulation inside - blood carries heat generated in muscles to the skin where it will be lost from the body (also insulation of fat and wool in animals)

Question 22

Water has ____ buoyancy, viscosity, thermal conductivity, and specific heat capacity than air.

Answer 22

greater