Question 1

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

Accepted Answer

An element is a pure substance consisting of only one type of atom, while a compound consists of two or more different elements chemically bonded together.

Question 2

A neutral atom of sodium ($$\mathrm{Na}) $$has an atomic number of 11 and a mass number of 23. How many neutrons does it have?

Accepted Answer

12

Question 3

Which of the following atoms can form the greatest number of covalent bonds, based on its valence electrons?

Accepted Answer

Carbon ($$\mathrm{C}$$), with 4 valence electrons

Question 4

Given the electronegativities: $$\mathrm{H} (2.1$$), $$\mathrm{O} (3.5$$), $$\mathrm{C} (2.5$$), which bond is most polar?

Accepted Answer

$$\mathrm{O-H}$$

Question 5

Which statement correctly describes the difference between ionic and covalent bonds?

Accepted Answer

Ionic bonds involve the transfer of electrons from one atom to another, resulting in charged ions, while covalent bonds involve the sharing of electrons between atoms.

Question 6

Water molecules are able to form hydrogen bonds with each other because:

Accepted Answer

The partial negative charge on oxygen and partial positive charge on hydrogen allow for attraction between molecules.

Question 7

Which property of water is most responsible for its ability to moderate temperature in living organisms?

Accepted Answer

Its high specific heat capacity

Question 8

A scientist is testing the effect of sunlight on plant growth. Which is the independent variable in this experiment?

Accepted Answer

Amount of sunlight the plants receive

Question 9

If a solution has a hydrogen ion concentration of $$[\mathrm{H}^+] = 1 	imes 10$$^{-4}$$~\mathrm{M}$$, what is its pH?

Accepted Answer

$$4$$

Question 10

Which of the following substances is most likely to dissolve readily in water?

Accepted Answer

A polar molecule such as glucose

Question 11

Which of the following best describes an acid in terms of hydrogen ion concentration and pH?

Accepted Answer

An acid has a high concentration of $$\mathrm{H}^+$$ ions and a low pH (below 7).

Question 12

A student observes that salt ($$\mathrm{NaCl}) $$dissolves easily in water. Which property of water explains this observation?

Accepted Answer

Water's polarity allows it to surround and separate charged ions.

Question 13

Which of the following is a controlled variable in an experiment testing the effect of fertilizer on plant growth?

Accepted Answer

Type of soil used for all plants

Question 14

A graph shows the relationship between temperature and enzyme activity. If enzyme activity increases with temperature up to a point, then sharply decreases, what conclusion can be drawn?

Accepted Answer

Enzymes have an optimal temperature range, above which they denature and lose activity.

Question 15

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 further apart in the solid state.

Question 16

Which step of the scientific method involves making a testable statement about what will happen in an experiment?

Accepted Answer

Hypothesis

Question 17

A molecule of ammonia ($$\mathrm{NH}_3) $$has a nitrogen atom bonded to three hydrogen atoms. Based on electronegativity, where would you expect the partial negative charge to be located?

Accepted Answer

On the nitrogen atom

Question 18

Which of the following scenarios best illustrates adaptation by natural selection?

Accepted Answer

A population of insects develops resistance to a pesticide over several generations.

Question 19

If a solution has a pH of 9, what is its hydrogen ion concentration ($$[\mathrm{H}^+]$$)?

Accepted Answer

$$1 	imes 10$$^{-9}$$~\mathrm{M}$$

Question 20

Which of the following is the dependent variable in an experiment measuring the effect of pH on enzyme activity?

Accepted Answer

The rate of enzyme activity measured

General Biology: Foundations, Scientific Method, and Chemistry of Life

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