# 2 Take Home Exam

Question 1

Valence shell

Answer 1

The outershell of any atom

Question 2

Atomic mass

Answer 2

Protons + neutrons taking isotope into account

Question 3

Isotope

Answer 3

Different versions of any given element with varying number of neutrons

Question 4

Ionic bonds

Answer 4

One atom wants to give up electrons while another atom wants to take electrons so both atoms satisfy Octet Rule

Question 5

Covalent bonds

Answer 5

Strong bonds created when two atoms share electrons in order to obtain a stable electron shell configuration

Question 6

Polar molecule

Answer 6

Amoleculecontainingpolarbonds where the sum of all the bond’s dipole moments is not zero

Question 7

Non-polar molecule

Answer 7

A molecule that has no separation of charge, so no positive or negative poles are formed

Question 8

Hydrogen bonds

Answer 8

Bonds that hold adjacent molecules and/or the folds of long, complex molecules together

Question 9

Dissociate

Answer 9

The process when ionic compounds dissolve inwater and their ions separate from one another. Also water dissociate into H+ and OH-

Question 10

pH scale

Answer 10

A rating system that measures a solutions acidity or alkalinity

Question 11

The atomic number defines which element a given atom is. Which atomic subunit does the
atomic number refer to?

Answer 11

Protons

Question 12

(a) Compare and contrast ionic bonds, covalent bonds and hydrogen bonds

Answer 12

a) Ionic and covalent bonds are both in a way similar to each other in the way they form. Ionic bonds form when one atom transfers electron(s) to another atom while covalent bonds form in a similar way with two atoms sharing two electrons. However hydrogen bonds result from an electrostatic attraction between a hydrogen atom and an electronegative atom. Covalent bonds are strong while hydrogen bonds are weak.

Question 13

(b) Provide two

examples of where hydrogen bonds play a role in biology.

Answer 13

b) Hydrogen bonds play a role in biology. For example holding together 1) double stranded DNA, 2) water, and 3) proteins

Question 14

List the four elements that comprise 96% of a healthy human body. Include in your answer the
percentage that each of these four elements contribute to the body mass.

Answer 14

Oxygen = 65% 
Carbon = 18.5% 
Hydrogen = 9.5%
Nitrogen = 3%

Question 15

List and describe the six special properties of water.

Answer 15

1. Cohesion
2. Adhesion
3. Great Solvent
4. High Heat of Evaporation
5. High Heat Capacity
6. Ice Floats

Question 16

Cohesion

Answer 16

clinging of like molecules; water has strong cohesion due to hydrogen bonds between water molecules

Question 17

Adhesion

Answer 17

the attraction of water molecules to charged surfaces. It is important because it is how water drop clings to a leaf or water rises up a capillary tube.

Question 18

Great Solvent

Answer 18

Water molecules surround other polar molecules and cause them to dissolve in water. It is important because where ever water travels, it brings along valuable chemicals, nutrients, and minerals with it.

Question 19

High Heat of Evaporation

Answer 19

When water vaporizes, it pulls heat away from the surface the water was on. It is important because it’s how

Question 20

High Heat Capacity

Answer 20

Water can absorb a large amount of heat energy with only small changes in its temperature. This property is extremely important because it helps to stabilize the temperature in all types of biological systems.

Question 21

Ice Floats

Answer 21

Water molecules in ice are farther apart than in liquid water so ice is less dense than liquid water and it floats. Which is important to the many organisms living under the ice and so that they can survive

Question 22

Why are biological systems sensitive to a change of pH (either more acidic or more basic conditions) in their ecosystem?

Answer 22

Biological systems are very sensitive to pH because cells and organisms must maintain a specific and constant pH in order to keep their enzymes in the optimum state of protonation