Bio U2 - 1.2

Question 1

Describe the structure of an atom (in terms of protons, neutrons and electrons).

Answer 1

Protons and Neutrons: Nucleus
Electrons: outer layers

Question 2

Contrast covalent, ionic and hydrogen bonds.

Answer 2

Ionic bonds: 2 ions, give and take electrons meaning one becomes positively charged and one negatively charged
Covalent bond: Sharing electrons. Very strong bonds
Hydrogen bonds: These bonds occur between the mildly positive bond of hydrogen to the mildly negative bond of oxygen

Question 3

Write the molecular formula for water and draw the atomic structure of the molecule.

Answer 3

H2O and notebook

Question 4

Describe the cause and effect of the polar nature of water.

Answer 4

Oxygen is very electronegative (such as the PONS elements) and thus attracts the electron it is sharing with hydrogen closer to its nucleus appear to be negatively charged. Polar means unequal sharing

Question 5

Describe where and how water is able to form hydrogen bonds.

Answer 5

This is because of the mildly positively charged hydrogen bonding with the mildly negative oxygen

Question 6

Contrast adhesion with cohesion.

Answer 6

Adhesion: water attaching to another surface through hydrogen bonding or attraction to an ionic charge

Cohesion: water attaching to another water through hydrogen bonding

Question 7

Outline an example of the cohesive property of water being of benefit to life.

Answer 7

1. Water cohesion allows insects such as the water strider to stay on the surface of the water through surface tension
2. Water cohesion creates a chain of water that allows for transport of water from roots to leaves of plants through the xylem
3. Water cohesion is responsible for high heat capacity of water, maintaining a relatively temperature stable internal and external environment for living organisms

Question 8

Outline an example of the adhesive property of water being of benefit to life.

Answer 8

Water sticks to the walls of the xylem through adhesion and makes it way from the roots to the leaves.

Question 9

Explain three thermal properties of water that are useful to living organisms.

Answer 9

Specific melting and boiling points, high specific heats, and high latent heat of vaporization

Question 10

Outline a benefit to life of water’s high specific heat capacity.

Answer 10

1. As water requires a relatively high amount of energy to heat, this allows organisms that have high percentages of water to not fluctuate their temperatures drastically and die
2. Density: because of water hydrogen bonding structure, solid water (ice) is less dense than water. So ice floats on the top of the lakes like blankets, insulating living organisms in the lake

Question 11

Outline a benefit to life of water’s high latent heat of vaporization.

Answer 11

As water takes an uncommonly high amount of energy to vaporize, because of the hydrogen bonds, it creates an effect called evaporative cooling after the water vaporizes. This makes for sweat to be an effective way of maintaining a stable body temperature and dissipate heat.

Question 12

Outline a benefit to life of water’s high boiling point.

Answer 12

1. Melting points and Boiling points: having a relatively high boiling temperature for such a light element means that water is found mostly in liquid and solid states on Earth, allowing for the existence of oceans

Question 13

Explain why is water such a good solvent.

Answer 13

Water is called the “universal solvent” because, through its hydrogen bonds, it is able to bond to more substances than any other liquid.

Question 14

List the types of molecules that water will dissolve.

Answer 14

Substances that dissolve in water are either polar or ionic compounds.

Question 15

State that polar and ionic molecules are hydrophilic.

Answer 15

Polar and Ionic molecules are hydrophilic because water’s partial charges are attracted.
Glucose has many polar covalent bonds between O and H that the water can hydrogen bond to.
Ions are hydrophilic because they have positive and negative changes that water is attracted to.

Question 16

State that non-polar, non-ionic molecules are hydrophobic.

Answer 16

These substances have no partial or full charges for water to be attracted to.

Question 17

Given a diagram of a molecular structure, determine if the molecule is hydrophobic or hydrophilic.

Answer 17

In notes on classroom

Question 18

Compare and contrast the physical properties of methane and water.

Answer 18

Water has a high density and heat capacity, while methane has lower melting points and boiling points, meaning that it is a gas surface temperature

Question 19

Explain why water and methane have different thermal properties based on their molecular structures.

Answer 19

Water has polar covalent bonds which result in partial charges while methane has non-polar covalent bonds that have no partial charges

Question 20

Explain sweating as a mechanism to cool the body.​

Answer 20

Sweat is mostly water, thus when sweat evaporates from the surface of the skin, it takes with it heat. The loss of this heat is evaporative cooling.

Question 21

State if the following molecules are hydrophobic or hydrophilic: glucose, amino acids, cholesterol, fats, oxygen, and sodium chloride.

Answer 21

Hydrophilic: Glucose, Amino acids, and Sodium Chloride (ion)
Hydrophobic: Cholesterol, Fats, and Oxygen (O2 is non polar)

Question 22

​Outline the mechanism of transport in the blood of the following molecules: glucose, amino acids, cholesterol, fats, oxygen, and sodium chloride.

Answer 22

Blood is primarly water, thus hydrophilic substance can be dissolved in it and then transported. Glucose, Amino acids, and Ions are all dissolved and transported.
On the other hand, hydrophobic substances need other ways of being transported. Cholesterol and Fats are packaged into sacs that have hydrophobic insides and hydrophilic outsides. Oxygen is transported by red blood cells.

Question 23

List emergent properties that result from water molecules joining together via hydrogen bonds.

Answer 23

Cohesion, Adhesion, High surface tension, High specific heat, High Heat of vaporization, and the fact that ice floats

Question 24

State why scientists cannot prove without a doubt that hydrogen bonds exist between water molecules.

Answer 24

Since hydrogen bonds have yet to be observed, their presence has not been proven, but they would mathematically, observationally, and chemically explain the properties of water.