Question 1

Which of the following best describes the difference between an atom and an element?

Accepted Answer

An atom is the smallest unit of matter that retains the properties of an element, while an element is a substance made entirely of one type of atom.

Question 2

Which subatomic particle is responsible for the chemical properties of an atom, and where is it located?

Accepted Answer

Electron; located in the electron cloud surrounding the nucleus.

Question 3

What is the electrical charge of a neutron, and how does it affect the mass of an atom?

Accepted Answer

Neutral; it contributes to atomic mass but not to charge.

Question 4

Which of the following elements is most abundant in living organisms?

Accepted Answer

Oxygen ($$O)$$

Question 5

Given the molecular formula $$C_6H_{12}O_6$, what information does this provide?

Accepted Answer

It shows the number and type of atoms present in one molecule.

Question 6

Which of the following best describes a covalent bond?

Accepted Answer

A bond formed by the sharing of electron pairs between atoms.

Question 7

What is the difference between a polar and a nonpolar covalent bond?

Accepted Answer

Polar covalent bonds involve unequal sharing of electrons due to differences in electronegativity; nonpolar covalent bonds involve equal sharing.

Question 8

Which of the following best explains why water is a good solvent for ionic compounds?

Accepted Answer

Water molecules have partial charges that can surround and separate ions.

Question 9

Which of the following is a correct symbol for a potassium ion?

Accepted Answer

$$K^+$$

Question 10

What is a 'partial charge' and how does it form in a water molecule?

Accepted Answer

A partial charge is a slight charge formed by unequal sharing of electrons in a polar covalent bond.

Question 11

Which property of water allows insects to walk on its surface?

Accepted Answer

Surface tension due to cohesion between water molecules

Question 12

Which of the following best describes the difference between cohesion and adhesion?

Accepted Answer

Cohesion is the attraction between molecules of the same substance; adhesion is the attraction between molecules of different substances.

Question 13

Which of the following best describes an electrolyte?

Accepted Answer

A substance that dissociates into ions in water and conducts electricity.

Question 14

If a solution has a pH of 3, which of the following statements is true?

Accepted Answer

The solution has a high concentration of hydrogen ions ($$H^+) $$and is acidic.

Question 15

Which of the following best describes the role of valence electrons in chemical bonding?

Accepted Answer

Valence electrons are the electrons in the outermost shell and are involved in forming chemical bonds.

Question 16

Which of the following is a correct description of an ion?

Accepted Answer

An atom that has gained or lost electrons, resulting in a net charge.

Question 17

Which property of water is most important for regulating temperature in living organisms?

Accepted Answer

High heat of vaporization

Question 18

Which of the following best explains why ice floats on water?

Accepted Answer

Ice is less dense than liquid water because hydrogen bonds hold water molecules farther apart in the solid state.

Question 19

Which of the following is a correct example of a macromolecule?

Accepted Answer

DNA

Question 20

A solution is made by dissolving 10 g of NaCl in 100 mL of water. In this scenario, which is the solute and which is the solvent?

Accepted Answer

NaCl is the solute; water is the solvent.

Chemical Context of Life: Key Concepts and Vocabulary

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