Chemical Basis of Life

Question 1

What is matter made up of?

Answer 1

Elements (basic substances)

Question 2

What is the nucleus surrounded by?

Answer 2

Electrons

Question 3

What subatomic particle is represented by an element’s atomic number?

Answer 3

Protons. The atomic number represents the amount of protons found in the nucleus of an atom of that element.

Question 4

What charge do electrons, protons, and neutrons have?

Answer 4

Electrons have a charge of -1. Protons have a charge of +1. Neutrons have no charge (they are neutral as per the name).

Question 5

In an uncharged atom, the number of protons is equal to the number of what?

Answer 5

Electrons

Question 6

What is an electron cloud?

Answer 6

A three-dimensional space in which electrons travel freely. The electron cloud is made up of energy levels/energy shells and orbitals.

Question 7

What is the energy level closest to the nucleus?

Answer 7

1. The number increases as we get farther away from the nucleus.

Question 8

Which energy level has the most energy?

Answer 8

The energy level farthest from the nucleus.

Question 9

How many electrons can the inner shell have? How many electrons can the subsequent (valence) shells have?

Answer 9

The innermost shell can have maximum 2 electrons. Valence shells/the outer shells of the electron can have a maximum of 8 electrons.

Question 10

What makes an atom stable?

Answer 10

They are more stable when every electron is paired and most stable when their valence level is full.

Question 11

Which atoms are unstable?

Answer 11

Atoms with unpaired or partially filled valence levels. These atoms will easily gain or lose electrons in order to obtain a more stable configuration.

Question 12

What is a covalent bond?

Answer 12

A bond formed between atoms when they share electrons. They are the strongest type of chemical bond. They result in a molecule.

Question 13

What is a molecule?

Answer 13

Two or more atoms held together by covalently shared electrons.

Question 14

What is a compound?

Answer 14

A compound is formed when two or more different atoms bond together chemically to create a unique substance (e.g., H2O, CH4).

Question 15

What results in a molecular element?

Answer 15

Two atoms of the same element covalently bonded (e.g., O2).

Question 16

What are charged atoms called?

Answer 16

Ions

Question 17

How can an uncharged electron become more stable?

Answer 17

• An uncharged electron may be more stable if its valence level loses one or more electrons and becomes positively charged. It becomes a positively charged particle or a positive ion.
• Similarly, an atom that gains one or more electrons to fill its valence level becomes a negative ion.

Question 18

What is an ionic bond?

Answer 18

• Negative and positive ions, being oppositely-charged, are attracted to each other which forms an ionic bond (e.g., NaCl [sodium chloride/table salt]).
• Weaker than covalent bonds

Question 19

What makes a molecule polar?

Answer 19

• Having regions of partial charge (e.g., a molecule with a weak, partial negative in one region of the molecule and a partial positive charge in another region).

Question 20

Describe a hydrogen bond

Answer 20

• Hydrogen bonds are formed between water molecules.
• Water molecules (with a net charge of 0) have a partial negative charge near the oxygen atom and a partial positive charge near each of the hydrogen atoms.
• When water molecules are close together, their positive regions are attracted to the negatively charged regions of nearby regions , vice versa. The force of attraction is a hydrogen bond.
• A weak chemical bond that temporarily holds separate molecules together.

Question 21

When do chemical reactions occur?

Answer 21

• Chemical reactions occur when molecules interact with each other to form one or more molecules of another type.
• Chemical reactions that occur within the cell provide energy, nutrients, and other products that allow the organism to function.

Question 22

Describe the composition of a chemical reaction equation

Answer 22

Chemical reactions are symbolized by an equation where the reaction molecules (reactants) are shown on the left side and newly formed molecules (products) are on the right side, with an arrow indicating the direction of the reaction.

Question 23

What does a decomposition reaction look like?

Answer 23

AB —> A +B

Question 24

What does a simple combination reaction look like? (Reverse of decomposition)

Answer 24

A +B —> AB

Question 25

What does a replacement/displacement reaction look like? (When one compound breaks apart and forms a new compound with a free reactant)

Answer 25

AB + C —> AC + B

Question 26

What are reactions that require energy called?

Answer 26

Endothermic reactions

Question 27

What are reactions that release energy called?

Answer 27

Exothermic reactions.

Question 28

What does the first law of thermodynamics (also known as the law of conservation of matter and energy) state?

Answer 28

It states that matter and energy of the reactants must equal that of the products.

Question 29

What does the second law of thermodynamics (or the law of increasing disorder or entropy) state?

Answer 29

It states that all reactions increase energy disorder in a system, which tends to diminish its availability for cellular use.

*So, although we know from the first law that energy must be equal on both sides of a reaction, reaction processes also tend to degrade the potential energy into a form that cannot perform any cellular work.

Question 30

What is the energy available to perform the work of a reaction known as?

Answer 30

Free energy

Question 31

What quality of water keeps it from disturbing processes within cells that require light (such as photosynthetic and light-sensing cells)?

Answer 31

The transparent quality of water.

Question 32

In what unique way does water respond to temperature change (cold)?

Answer 32

• Unlike most substances which contract upon become a solid, water expand as it solidifies (freezes), forming a loose lattice structure (crystal).
• The crystalline form of frozen water (ice) makes it less dense than liquid water.
• Lakes and other bodies of water freeze from the top first, insulating the water and organisms below from, harsh temperature changes.

Question 33

In what unique way does water respond to temperature change (heat)?

Answer 33

• Water has a high specific heat. It resists changes in temperature.
• The presence of many hydrogen bonds allows water to absorb a large amount of thermal heat without a great change in temperature.
• The presence of water in an environment regulates harsh temperature changes.

Question 34

What gives water a high surface tension?

Answer 34

Hydrogen bonds. This high surface tension allows small particles and organisms to rest on the surface.

Question 35

What kind of molecule is water? Why is it special?

Answer 35

• Water is a polar molecule.
• This allows water to dissolve many kinds of organic and inorganic substances.
• This property (polarity) promotes several biological processes like muscle contraction, nerve stimulation, and transport across membranes (permeability).

Question 36

What does an acid do when dissolved in water?

Answer 36

An acid is a chemical that donates protons (H+ ions) when dissolved in water.

Question 37

What does a base do when dissolved in water?

Answer 37

An base is a chemical that accepts protons (H+ ions) or donates hydronium ions (OH-) when dissolved in water.

Question 38

The presence of a base does what to H+ ions?

Answer 38

• The presence of the base lowers the concentration of H+ ions (due to OH- and H+ combining to form water [H20]).
• Acids and bases tend to neutralize each other when dissolved together in water.

Question 39

The neutralization of an acidic solution with a basic solution produces what?

Answer 39

The neutralization produces water and a salt (an ionic compound like NaCl, CaCl, any cation) from the original acid and base molecules.

Question 40

What is acidity a measure of?

Answer 40

A measure of H+ ions in a solution and is described by the pH scale.

Question 41

What are the ranges on the pH scale?

Answer 41

• The pH of a substance can range from 0 (highest possible concentration/very acidic) to 14 (lowest possible/very alkaline or basic).
• a pH of 7 is neutral (like pure water).

Question 42

What is a buffer?

Answer 42

• A buffer is an aqueous (water based) combination of a weak acid and its conjugate base, or a weak base and its conjugate acid.
• A buffer solution resists a change in pH when new H+ or OH- ions are added. This is because the H+ ions react with the weak base to form water/the OH- ions react with the weak acid to form water.
• Buffering capacity is exhausted when either the weak acid or weak base is used up.