Question 1

Which of the following statements best explains why water is an excellent solvent for ionic compounds such as NaCl?

Accepted Answer

Water is polar, so its partially positive and negative ends can surround and separate the ions.

Question 2

A carbon atom has an atomic number of 6 and a mass number of 14. How many neutrons does this atom have?

Accepted Answer

$$14 - 6 = 8$$ neutrons

Question 3

Which property of water allows it to moderate temperature changes in organisms and environments?

Accepted Answer

Water's high specific heat due to hydrogen bonding

Question 4

Which of the following best describes a covalent bond?

Accepted Answer

A bond formed by the sharing of electron pairs between atoms

Question 5

Why does ice float on liquid water?

Accepted Answer

Ice is less dense than liquid water because hydrogen bonds hold water molecules further apart in a solid state

Question 6

Which of the following is true about isotopes of an element?

Accepted Answer

They have the same number of protons but different numbers of neutrons

Question 7

A sodium atom (Na) has 11 protons and 12 neutrons. What is its mass number?

Accepted Answer

$$11 + 12 = 23$$

Question 8

Which of the following best explains why water molecules are cohesive?

Accepted Answer

Hydrogen bonds form between water molecules, holding them together

Question 9

Which statement about valence electrons is correct?

Accepted Answer

Valence electrons are the electrons in the outermost shell and determine chemical bonding

Question 10

A molecule of methane ($$CH_4) is $$formed when carbon shares electrons with four hydrogen atoms. What type of bond is formed between carbon and hydrogen?

Accepted Answer

Covalent bond

Question 11

Which of the following best describes the difference between hydrophilic and hydrophobic substances?

Accepted Answer

Hydrophilic substances dissolve in water, while hydrophobic substances do not

Question 12

Which of the following is a real-life example of water's adhesive property?

Accepted Answer

Water molecules sticking to the sides of a glass tube, allowing capillary action

Question 13

If an atom has 17 protons, 18 neutrons, and 17 electrons, what is its atomic number and mass number?

Accepted Answer

Atomic number = 17, Mass number = $$17 + 18 = 35$$

Question 14

Which of the following best explains why carbon is able to form large, complex molecules?

Accepted Answer

Carbon can form four covalent bonds due to its four valence electrons

Question 15

Which of the following scenarios demonstrates the importance of water's high heat of vaporization in living organisms?

Accepted Answer

Sweating cools the human body as water evaporates from the skin, removing heat

Question 16

Which of the following is true about hydrogen bonds in water?

Accepted Answer

They form between the hydrogen atom of one water molecule and the oxygen atom of another

Question 17

A molecule has a region with a partial positive charge and a region with a partial negative charge. What type of molecule is this?

Accepted Answer

Polar molecule

Question 18

Which of the following best describes the octet rule as it applies to atoms?

Accepted Answer

Atoms are stable when their outer shell contains 8 electrons

Question 19

Which of the following is a direct consequence of water's polarity?

Accepted Answer

Water can dissolve many ionic and polar substances

Question 20

Which of the following best explains why oil does not dissolve in water?

Accepted Answer

Oil is nonpolar and cannot interact with polar water molecules

Atoms, Ions, Molecules, and Water: Foundations of Chemical Evolution in Biology

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