Chapter 2 - Chemical Basis of Life & Ocean Acidification

Question 1

What is matter? What are the different phases of matter?

Answer 1

Matter is anything that occupies space and has mass. Solid, liquid, gas.

Question 2

What is an atom?

Answer 2

An atom is the smallest unit of matter which still displays the characteristic properties of an element. Made of protons, neutrons and electrons.

Question 3

What is an element?

Answer 3

An element is a substance that cannot be broken down to other substances by ordinary chemical means. All matter is made of elements.

Question 4

What is a molecule?

Answer 4

Molecules are formed when 2 or more atoms (of the same element) combine together.

Question 5

What is a compound?

Answer 5

A compound is a substance consisting of two or more elements combined in a fixed ratio. Compounds can have very different properties than its individual components.

Question 6

Only _______(#) elements make up 96% of what is inside of life. What are they?

Answer 6

Four. Oxygen, Carbon, Hydrogen and Nitrogen. (from biggest to smallest)

Question 7

What elements make up 98% of all living matter?

Answer 7

Oxygen, Carbon, Hydrogen, Nitrogen, Phosphorus, and Sulfur! (from biggest to smallest)

CHNOPS!!

Question 8

What goes into carbohydrates and proteins? (Related to: What elements make up 96% of what is inside of life?)

Answer 8

Carbohydrates = CHO (Carbon, Hydrogen, Oxygen)

Proteins = primarily CHNO…and a bit
of S. (Carbon, Hydrogen, Nitrogen, and Oxygen… and Sulfur)

Question 9

What are the 3 subatomic particles?

Answer 9

Protons, neutrons and electrons.

Question 10

What are the charges of the 3 subatomic particles?

Answer 10

Protons are positive.
Neutrons are neutral.
Electrons are negative.

Question 11

How do the charges of protons and electrons interact? What is the overall charge of a “normal” atom?

Answer 11

Opposites attract which is why the electrons don’t fly off.

The charges of protons and electrons cancel each other out.
Normally # electrons = # protons so the atoms are electrically balanced, or neutral.

Question 12

How do the charges of electrons interact with each other?

Answer 12

Electrons are repelled by one another because they have the same charge.

Question 13

What are the sizes of the 3 subatomic particles? Where are they located within the atom?

Answer 13

Protons and neutrons are bigger, approximately the same size, and occupy the nucleus.

Electrons are teeny tiny and occupy “orbitals” or “energy shells” around the nucleus.

Atoms are mostly empty space!

Question 14

What is an atomic orbital?

Answer 14

Specific three dimensional zones around the nucleus. A cloud-like region in which there is a 90% probability of finding the electron in motion around the nucleus.

Question 15

Which subatomic particle is responsible for defining the element?

Answer 15

Protons. All atoms of a particular element have the same number of protons.

Question 16

Which subatomic particle is responsible for an element’s reactivity?

Answer 16

The atom’s reactive properties are based on the electrons.

Question 17

What is the atomic number?

Answer 17

The number of protons specific to an element.

For example, carbon has 6 and oxygen has 8.

Question 18

What is the atomic mass?

Answer 18

The mass of a single isotope or single atom. The sum of an atom’s neutrons and protons.

i.e. Carbon, with its six protons and six neutrons has an atomic mass of 12

Question 19

What is the atomic weight?

Answer 19

The average weight of an element with respect to all its isotopes and their relative abundances.

Question 20

What is an isotope? Do these behave differently?

Answer 20

An atom with more or less neutrons than normal (normally protons = neutrons). The atom behaves the same as normal but has a different atomic mass. Some may be radioactive.

Question 21

How is radioactivity related to isotopes? How can radioactivity be useful?

Answer 21

Some isotopes may be radioactive (unstable, degrades over time and gives off radiation).
Can be used as tracers in experiments, in medical imaging and to date things.

Question 22

What is an ion?

Answer 22

An atom or molecule with a net electrical charge (+/-). Formed by the addition or subtraction of electrons from a neutral atom.

Question 23

What is a cation?

Answer 23

A positively charged ion.

Question 24

What is an anion?

Answer 24

A negatively charged ion.

Question 25

How many electrons fit into a single orbital? How are orbitals related to energy?

Answer 25

Only two electrons can occupy an orbital at any one time. Atoms with more than two electrons have a series of orbitals at increasing distances from the nucleus. The further an electron is from the nucleus, the greater its energy

Question 26

How many electrons and orbitals fit into the first shell and second shell?

Answer 26

The first shell contains 1 orbital and can hold 2 electrons. The second shell contains 4 orbitals and can hold 8 electrons.

Question 27

What do we call electrons in the outer shell that dictate how the atom reacts?

Answer 27

The outer shell is the valence shell, and the electrons in it are valence electrons. They determine the chemical properties of the atom and are available for chemical bonding.

Question 28

What is a stable number of electrons in a valence shell?

Answer 28

Most stable when full. Most of the elements important in biology need eight electrons in their outermost shell.

Question 29

What is a molecular orbital?

Answer 29

When the orbitals of two atoms overlap and are shared. Creates a “chemical bond” that can compress, stretch, bend to a certain extent and rotate.

Question 30

What are the three basic types of chemical bonds?

Answer 30

Covalent Bonds can be nonpolar (equal sharing) or polar (unequal sharing).
Ionic Bonds (one donates, one receives, creating ions)
Hydrogen Bonds

Question 31

What is a double (or triple) bond?

Answer 31

Formed when atoms share two (or three) pairs of electrons. Prevents the rotation unlike single bonds.
i.e. O2 has a double bond.

Question 32

What is electronegativity? How does it affect bonds?

Answer 32

The ability to attract electrons from other atoms in a molecule. The closer the outer shell is to being full the more electronegative the atom. If a bond forms between two atoms with different electronegativities the bond will be “polarized”.

Question 33

Do electrons closer to or further from the nucleus have a higher energy level?

Answer 33

The further an electron is from the nucleus, the greater its energy.

Question 34

What are polar bonds and why is this important for water (H2O)?

Answer 34

Polar covalent bonds include the unequal sharing of an electron.
In H2O the oxygen holds the electrons closer giving it a slight negative change and the hydrogen a slight positive change. This allows water to hydrogen bond!

Question 35

What are chemical reactions, reactants and products?

Answer 35

The making and breaking of chemical bonds, leading to changes in the composition of matter. It starts with the reactants and creates the products.

Question 36

What is a hydrogen bond? What compound is this most relevant to?

Answer 36

A weak electrical attraction between polar molecules. A slightly positive hydrogen of one molecule attracts a slightly negative atom from another molecule. Usually shown as a dotted line.

Water’s two hydrogen atoms form a “V” shape. H2O will hydrogen bond to other H2Os.

Question 37

What are some of the unique properties of water because of hydrogen bonding? (7 properties)

Answer 37

Freezing point (O°C) and boiling point (100°C) are higher than expected so it’s usually liquid (good for chem reactions).
Universal solvent.
The most abundant liquid.
High heat of vaporization (water absorbs lots of heat to evaporate, evaporative cooling) and high heat capacity/specific heat (changes temp. slow, buffer).
Strong cohesion/adhesion(plants! and water tension/meniscus).
Ice floats, it’s less dense than the liquid water due to its lattice structure (lake life).

Question 38

What is cohesion/adhesion?

Answer 38

Cohesion: The tendency of molecules of the same kind to stick together. (plants use this to draw up water)

Adhesion: The tendency of molecules of one kind to stick to another kind. (meniscus!)

Question 39

What is heat? What is temperature?

Answer 39

Heat – the total amount of energy associated with molecular movements.

Temperature is the intensity of heat.

Question 40

How is heat related to hydrogen bonds?

Answer 40

Heat must be absorbed to break the H-bonds of water. This requires much more heat than if there were no H-bonds.

When H-bonds form – (as when ice forms a lattice structure), heat is released.

Question 41

What is a solution?

Answer 41

A liquid that is a mixture of 2 or more substances.

Question 42

What is an aqueous solution?

What is a saturated solution?

Answer 42

A solution where water is the solvent.

A solution that cannot dissolve any more solute.

Question 43

What is a solvent? What’s a common solvent?

Answer 43

The dissolving agent in a solution – usually a liquid. Water is the most versatile solvent known because of its polarity.

Question 44

What is a solute?

Answer 44

A substance that is dissolved in a solution (often a solid).

Question 45

What is the hydrogen ion concentration and pH of pure water?

Answer 45

In one litre of pure water the H+ concentration is 1x10-7 moles and the pH is 7 (neutral).

Question 46

How does the pH (the potential of Hydrogen) scale work?

Answer 46

pH describes how acidic or basic a solution is on a scale of 0 to 14. It is the negative log10 of the hydrogen ion concentration.
Acids = 0 to 7, add H+ to solutions.
Neutral = 7, equal H+ and OH-
Bases = 7 to 14, add OH- to solutions (a.k.a. subtracting H+).

Question 47

How does the pH scale increase/decrease?

Answer 47

It’s a logarithmic scale, so every change in pH of 1 unit represents a 10-fold change in the [H+] of a solution.
pH 6 = 10 x more H+ than 7
pH 5 = 10 x 10 = 100 times more H+ than 7

Question 48

What is a buffer? Why is it important?

Answer 48

Buffers are solutions that resist changes in pH when an acid or a base are added to them.
The molecules and chemistry of life function within very narrow ranges of pH.

Question 49

What is the bicarbonate buffer system?

Answer 49

A buffering system in mammalian blood (and seawater). This system is in equilibrium and is reversible. When you add CO2 (by breathing) you shift the equation to the right and get more H+, and vice versa.

Question 50

What causes acid rain? What is it’s pH?

Answer 50

Mostly burning fossil fuels (sometimes volcanoes, metal smelting) = sulphurous and nitrous oxides = sulphuric and nitric acids = acid rain, snow, fog, hail, or even dust. Regular rain = pH 5.6, acid rain = pH 4.2 to 4.4

Question 51

What are some of the effects of acid rain?

Answer 51

Additional acid alters the pH of environments. Run off adds toxic elements into aquatic systems. Dissolves shells. Leaches toxins from soil, robs nutrients, makes plants weak. Damages roots, leaves and bacteria.

Question 52

What causes ocean acidification?

Answer 52

The increase in CO2 from fossil fuel burning over the past 150 years. Carbon dioxide dissolves into water and becomes carbonic acid (H2CO3) which adds more H+ to the water.

Question 53

What happens to the pH of the oceans as they become more acidic (or less basic)? What’s the approx. ocean pH?

Answer 53

The pH becomes lower. Prior to industrialization, oceans were slightly alkaline with a pH of 8.2, today it is about 8.1 (which is significant, pH is logarithmic).

Question 54

How does ocean acidification affect sea creatures?

Answer 54

A lower pH dissolves calcium carbonate shells and exoskeletons.
Coral reefs require carbonate ions for their skeletons. Coral reef ecosystems are safe havens. Many shelled organism are important to food webs.