Study Questions #1: Chemistry

Question 1

Why do biologists need to know a lot of chemistry?

Answer 1

• life is made of chemicals
• life converts nutrients into biochems by chem rxns
• life is chem with a purpose
• necessary to understand life

Question 2

What is an atom and what are atoms made of?

Answer 2

Atoms are the smallest particles with unique chemical properties.
- made of nucleus of protons and neutrons surrounded by electrons

Question 3

What is an element?

Answer 3

atoms with the same atomic number and the same chemical properties

Question 4

What is the difference between atomic number and atomic mass?

Answer 4

Atomic number: # of protons

Atomic mass: # of protons and # of neutrons

Question 5

Why is the atomic number important?

Answer 5

• # of protons
• # of electrons
• identifies element
• chemical/physical properties
• reactivity (determined by # of electrons in valence shell)

Question 6

What are isotopes?

Answer 6

• different forms of the same element

- different atomic mass because different number of neutrons

Question 7

What is radioactive decay and why is it useful?

Answer 7

emission of particles from unstable isotopes; involves release of energy; nucleus decays
(used for carbon dating and medicine)

Question 8

What is the difference between a cation and an anion?

Answer 8

cation: ion with more positive charge (more protons than electrons)
anion: ion with negative charge (more electrons than protons)

Question 9

What is the difference between oxidation and reduction?

Answer 9

oxidation: lose electrons (more positive)
reduction: gain electrons (more negative)

*Both are movements of electrons (redox reactions, oxidation and reduction occur at the same time)

Question 10

Why are the redox reactions important for living organisms?

Answer 10

When electrons move they take their energy with them; redox reactions are used for energy transfer
(Ex: photosynthesis, Kreb’s cycle)

Question 11

What is the difference between an orbital and an electron energy level?

Answer 11

electron energy level a.k.a shell
- can be made of 1 or more orbitals
orbital is probable location of an electron
- can have 0, 1, or 2 electrons
- orbitals have distinct shapes

Question 12

What is the valence shell?

Answer 12

electrons in outermost shell

Question 13

Why do valence electrons determine the chemical properties of an element?

Answer 13

• the ones that interact/ready to react

- atoms want to fill valence shell

Question 14

Why do elements whose atomic numbers differ by eight have similar chemical properties?

Answer 14

they have the same number of electrons in the valence shell, which controls their reactivity
- octet rule

Question 15

Why is helium chemically inert?

Answer 15

valence shell is filled

1st shell: 2 electrons
2nd shell: 8 electrons
3rd shell: 8 electrons

Question 16

Why is bromine very reactive?

Answer 16

needs one electron to fill valence shell

takes electron from another atom

Question 17

What is the difference between an ionic and a covalent bond?

Answer 17

ionic: electrons are transferred, causes formation of cation and anions
(Ex: giving away a drink when you have a lot)

covalent: electrons are shared
- stronger than ionic
- contains more energy than ionic bond
(Ex: splitting the last drink with straws)

Question 18

What sorts of bonds do you expect lithium to form? (#3)

Answer 18

Ionic Bonds: give away electron

Question 19

What sorts of bonds do you expect phosphorous to form? (#15)

Answer 19

Covalent Bond

Question 20

Why are the weak bonds important for living organisms?

Answer 20

They are easily made and easily broken. It makes it possible to rearrange quickly

Question 21

What sorts of weak bonds are commonly found inside living organisms?

Answer 21

• Ionic bonds in solution
• Hydrogen bonds (bind 2 strands of DNA)
• Van der Waals bonds
• Hydrophobic Interactions

Question 22

What is a hydrogen bond?

Answer 22

attraction due to partial charge resulting from unequal electron distribution

Question 23

What are van der Waals interactions?

Answer 23

• atoms with partial charges attracted to atoms with opposite charge
• due to transient polarity of electrically neutral molecules
• molecules position themselves at optimum distance
• when too close electrons repel each other

Question 24

What are four factors which influence the rates of chemical reactions?

Answer 24

1. Concentration of Reactants (more reactants; faster rate of reaction)
2. Concentration of Products (more products; slower rate of reaction)
3. Temperature (higher temperature; faster reaction)
4. Catalysts (increase rate of reaction;
   Ex: Enzymes)