General ---------Biology----------------------------------------------------- ------------------Online--------------------------------------- Ch. 2 The Chemical Context of Life

Answer multiple choice questions 1-21, transfer your answers to a scantron and turn in at start of class.  Do  the discussion questions, but do not turn anything in;  we may discuss these questions in class. 

1. An atomic form of carbon containing different numbers of 
     neutrons is 
     a. an isotope. 
     b. an ion. 
     c. a polar atom. 
     d. an isomer. 
     e. radioactive. 

2. Oxygen has an atomic number of 8. Therefore, it must have 
             1. 8 protons. 
             2. 8 electrons. 
             3. 8 neutrons. 
     a. 1 
     b. 2 
     c. 3 
     d. Only 1 and 2 are correct. 
     e. 1, 2, and 3 are correct. 

3. Each element is unique and different from other elements because of 
     its 
     a. atomic weight (weight of protons, neutrons and electrons). 
     b. atomic number (number of protons). 
     c. mass number (number of protons, neutrons). 
     d. atomic weight and atomic number. 
     e. atomic weight, atomic number, and mass number. 

4. What do atoms form when they share electron pairs? 
     a. elements 
     b. ions 
     c. aggregates 
     d. isotopes 
     e. molecules 

5. Results from an unequal sharing of electrons between atoms. 
      a. nonpolar covalent molecule 
      b. polar covalent bond 
      c. ionic bond
      d. hydrogen bond 
      e. hydrophobic interaction 

6. Best explains attraction of water molecules to each other. 
      a. nonpolar covalent molecule 
      b. polar covalent bond 
      c. ionic bond 
      d. hydrogen bond 
      e. hydrophobic interaction 

7. One difference between carbon-12 and carbon-14 is that carbon-14 has 
            1. 2 more protons than carbon 12. 
            2. 2 more electrons than carbon 12. 
            3. 2 more neutrons than carbon 12. 
     a. 1 
     b. 2 
     c. 3 
     d. Only 1 and 3 are correct. 
     e. 1, 2, and 3 are correct. 

8. When two atoms are equally electronegative, they will interact to 
     form 
     a. equal numbers of isotopes. 
     b. ions. 
     c. polar covalent bonds. 
     d. nonpolar covalent bonds. 
     e. ionic bonds. 

9. How do isotopes differ from each other? 
     a. number of protons 
     b. number of electrons 
     c. number of neutrons 
     d. valence electron distribution 
     e. ability to form ions 

10. The combining properties of an atom depend on the number of 
     a. valence shells in the atom. 
     b. orbitals found in the atom. 
     c. electrons in each orbital in the atom. 
     d. electrons in the outer valence shell in the atom. 
     e. hybridized orbitals in the atom. 

11. The atomic mass of an element can be easily approximated by adding 
     together the number of (recall that electrons weigh almost nothing). 
     a. protons and neutrons. 
     b. electron orbitals in each energy level. 
     c. protons and electrons. 
     d. neutrons and electrons. 
     e. isotopes of the atom. 

12. Atoms whose outer electron shells contain eight electrons tend to 
     a. form ionic bonds in aqueous solutions. 
     b. form covalent bonds in aqueous solutions. 
     c. be particularly stable and nonreactive. 
     d. be particularly unstable and very reactive. 
     e. be biologically important since they are present in organic 
        molecules. 

13. Which of the following is a trace element that is essential to 
     humans? 
     a. nitrogen 
     b. calcium 
     c. iodine 
     d. carbon 
     e. oxygen 

14. Which of the following is a polar covalent bond? 
     a. H-H
     b. C-C 
     c. H-O 
     d. C-H 
     e. O-O 

15. A covalent bond is likely to be polar when 
     a. one of the atoms sharing electrons is much more electronegative 
        than the other atom. 
     b. the two atoms sharing electrons are equally electronegative. 
     c. the two atoms sharing electrons are of the same element. 
     d. it is between two atoms that are both very strong electron 
        acceptors. 
     e. it joins a carbon atom to a hydrogen atom. 
 
 

16. The number of protons in an atom with the atomic number of 5. 
     a. 1 
     b. 2 
     c. 3 
     d. 4 
     e. 5 

17. The maximum number of electrons in the 1, or "s", orbital. 
     a. 1 
     b. 2 
     c. 3 
     d. 4 
     e. 5 

18. Which four elements make up approximately 96% of living matter? 
     a. carbon, hydrogen, nitrogen, and oxygen 
     b. carbon, sulfur, phosphorus, and hydrogen 
     c. oxygen, hydrogen, calcium, sodium 
     d. carbon, sodium, chlorine, magnesium 
     e. carbon, oxygen, sulfur, calcium 

19. A covalent chemical bond is one in which 
     a. electrons are removed from one atom and transferred to another 
        atom so that the two atoms become oppositely charged. 
     b. protons or neutrons are shared by two atoms so as to satisfy the 
        requirements of both. 
     c. outer shell electrons are shared by two atoms so as to 
        satisfactorily fill the outer electron shells of both. 
     d. outer shell electrons on one atom are transferred to the inner 
        electron shells of another atom. 
     e. the inner shell electrons of one atom are transferred to the 
        outer shell of another atom. 

20. Which of the following best explains the distinction between biology 
     and chemistry? 
     a. Biologists study living things while chemists study nonliving 
        things. 
     b. Biology has a hierarchy of structural levels while chemistry does 
        not. 
     c. Chemists study molecules while biologists do not. 
     d. Biological systems have emergent properties while chemical 
        systems do not. 
     e. There is no clear distinction because the two sciences are parts 
        of the same whole. 

21. Which of the following best describes a chemical equilibrium? 
     a. reactions continuing with no effect on the concentrations of 
        reactants and products 
     b. concentrations of products are high 
     c. reactions have stopped 
     d. reactions stop only when all the reactants have been converted to 
        products 
     e. equal concentrations of reactants and products 

   Use the answers below for 22-25..
   a.  a marriage made in heaven where the two partners are equal
   b.  two peas in a pod
   c.  a lock and key
   d.  a horse and carriage
   e.  a marriage made in heaven where one of the two partners takes more than an equal share

   22.  The endorphin molecule fits its protein receptor like

   23.  A nonpolar covalent bond is like 

   24.  A polar covalent bond is like

   Use the answers below for 25-27.
   a.  kinetic energy...the energy of motion
   b.  chemical energy
   c.  nuclear energy

   25.  The energy that results from splitting protons and neutrons apart in an atoms nucleus.

   26.  The energy that results from hitting a golf ball.

   27.  The energy that results from breaking a covalent bond.

Use the following for 28 and 29.
   a.  raises an electron to a higher energy level and is stored in that electron as long as it
        remains at the higher energy level.
   b.  the energy stored in the electron is released as electromagnetic radiation (heat and/or light)

  28.  When an atom absorbs energy, say from sunlight, heat or from being struck by another atom,
the absorbed energy

  29.  When an electron falls back to its original energy level
 

Discussion Question

Chemical Bond Question

Covalent bond energy, or

Chemical energy, or

Calories

Explain, in one paragraph of three sentences, the mechanism that allows energy to be stored in a covalent bond, such as the one illustrated below between two hydrogen atoms, i.e. hydrogen gas or H2.

This energy can be called chemical energy, or covalent bond energy.If the covalent bond is in food molecules, then it is called “caloric energy.”

Bring your answer to class and be prepared to read your answer to class.