Chemistry Comes to Life 2 Chemistry Comes to Life 1

1. An atom is made of protons and neutrons (in the nucleus) and electrons spinning around in orbital shells. The number of electrons always equals the number of neutrons the number of protons and neutrons the number of protons None of the above c. the number of protons

1. An atom is made of protons and neutrons (in the nucleus) and electrons spinning around in orbital shells. The number of electrons always equals Answer: c. the number of protons Explanation: Protons are positively charged and electrons are negatively charged. An equal number of protons and electrons insure the atom is electrically neutral. Neutrons have no electrical charge.

2. True or false? Isotopes differ in the number of electrons. B. False 4

2. True or false? Isotopes differ in the number of electrons. Answer: b. False Explanation: Isotopes differ in the number of neutrons. Isotopes of a same atom have similar properties because their number of protons (and electrons) are the same. Isotopes may have more or less neutrons than the original atom.

3. Weak bonds that form between water molecules or between the nucleotide bases of two strands of DNA are called ______ bonds. covalent compound hydrogen ionic C. hydrogen

3. Weak bonds that form between water molecules or between the nucleotide bases of two strands of DNA are called ______ bonds. Answer: c. hydrogen Explanation: Hydrogen bonds are weak attractions between partial charges in polar molecules such as in water molecules or nucleic acids.

4. Which property of water provides the cooling effect of sweating? Cohesiveness High heat capacity High heat of vaporization Surface tension C. High heat of vaporization

4. Which property of water provides the cooling effect of sweating? Answer: c. High heat of vaporization Explanation: Water has a high heat of evaporation, meaning that it takes a lot of energy to cause water to evaporate. Therefore, water molecules that evaporate carry away a lot of heat, cooling the surface.

5. Most body fluids are found in which range of the pH scale? All body fluids are of pH 7 (neutral). B. pH = 6–8

5. Most body fluids are found in which range of the pH scale? Answer: b. pH  6–8 Explanation: Most body fluids are close to the neutral pH value of 7. Buffers act to keep the pH in an acceptable range of 6–8.

6. Polymers are ______. broken down by hydrolysis macromolecules made by a dehydration process All of the above D. All of the above

6. Polymers are ______. Answer: d. All of the above Explanation: Polymers consist of many small molecules (monomers) linked together by hydration synthesis and broken down by hydrolysis. The long chain molecules are called macromolecules (meaning large molecules).

7. Triglycerides are so named because they are formed by a reaction between three fatty acid molecules and one ______. amino acid glucose glycerol lipid C. glycerol

7. Triglycerides are so named because they are formed by a reaction between three fatty acid molecules and one ______. Answer: c. glycerol Explanation: Triglycerides are composed of one molecule of glycerol joined to three fatty acids.

8. Enzymes are a type of ______, which function to ______. carbohydrate; build strength gland; form hormones cell; repair tissue protein; speed up chemical reactions D. protein; speed up chemical reactions

8. Enzymes are a type of ______, which function to ______. Answer: d. protein; speed up chemical reactions Explanation: Enzymes are substances that speed up chemical reactions without being consumed in the process.

9. Which of the following has the smallest size? A neutron A molecule of glucose An atom of oxygen A cell A. A neutron

9. Which of the following has the smallest size? Answer: a. A neutron Explanation: Subatomic particles (neutrons, electrons, and protons) combine to form atoms. Atoms combine to form molecules. Billions or even trillions of molecules combine to form cells.

10. Phospholipids have hydrophobic ______, and hydrophilic ______. heads; tails tails; heads glycerol; fatty acids amino acids; monomers B. tails; heads

10. Phospholipids have hydrophobic ______, and hydrophilic ______. Answer: b. tails; heads Explanation: The tails are lipid-soluble and “fear” (phobia) water (hydro) while the heads of phospholipids are water-soluble and “love” water (hydrophilic).

11. Solution A has a pH of 6. Solution B has a pH of 9 11. Solution A has a pH of 6. Solution B has a pH of 9. Which of the following statements is false? Solution A has 1000x more H than solution B. The concentration of H in solution B is 1 × 109 moles per liter. Both solutions A and B are acids. All of the above are true. C. Both solutions A and B are acids.

11. Solution A has a pH of 6. Solution B has a pH of 9 11. Solution A has a pH of 6. Solution B has a pH of 9. Which of the following statements is false? Answer: c. Both solutions A and B are acids. Explanation: A pH  7 is considered acidic and a pH  7 is considered basic. Thus solution A is an acid and solution B is a base.