Question 1

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

Accepted Answer

Hydrogen bonds in ice cause water molecules to spread apart, making ice less dense than liquid water.

Question 2

Which of the following elements makes up the highest percentage of the human body by weight?

Accepted Answer

Oxygen (O)

Question 3

A radioactive isotope of carbon has an atomic number of 6 and a mass number of 14. How many neutrons does it have?

Accepted Answer

$$14 - 6 = 8$$ neutrons

Question 4

Which property of water allows trees to transport water from their roots to their leaves?

Accepted Answer

Cohesion due to hydrogen bonding

Question 5

Which of the following statements about chemical reactions is correct?

Accepted Answer

Chemical reactions only rearrange matter; they do not create or destroy it.

Question 6

What type of bond is formed when two atoms share one or more pairs of electrons?

Accepted Answer

Covalent bond

Question 7

Which of the following best describes a trace element?

Accepted Answer

An element required in only very small amounts but essential for life

Question 8

A solution has a pH of 4. Which of the following statements is true?

Accepted Answer

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

Question 9

Which of the following is a real-world example of an ionic bond?

Accepted Answer

The bond between sodium and chlorine in table salt ($$NaCl)$$

Question 10

Why is water considered the 'solvent of life'?

Accepted Answer

Water can dissolve a wide variety of substances due to its polarity.

Question 11

Which of the following best explains why sweating cools the body?

Accepted Answer

Sweat absorbs heat as it evaporates, due to the breaking of hydrogen bonds.

Question 12

Which of the following is true about isotopes?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 13

Which property of water is most responsible for the high surface tension observed in a drop of water?

Accepted Answer

Hydrogen bonding between water molecules

Question 14

A patient receives radiation therapy for cancer. Which property of radioactivity is being used in this treatment?

Accepted Answer

Radioactivity can kill cells by damaging DNA.

Question 15

Which of the following best describes a chemical compound?

Accepted Answer

A substance containing two or more elements in a fixed ratio

Question 16

Which of the following is an example of a buffer in biological systems?

Accepted Answer

A substance that minimizes changes in pH

Question 17

Which of the following best explains why fossil age can be estimated using radioactive isotopes?

Accepted Answer

The ratio of two isotopes reveals how many half-lives have passed since the organism died.

Question 18

Which of the following is a real-life consequence of ocean acidification caused by atmospheric $$CO_2$$?

Accepted Answer

Death of coral reefs due to changes in water chemistry

Question 19

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

Accepted Answer

Only electrons are directly involved in chemical reactions and bonding.

Question 20

A sodium atom ($$Na) $$transfers an electron to a chlorine atom ($$Cl$$), forming $$Na^+$$ and $$Cl^-. $$What type of bond holds these ions together in table salt?

Accepted Answer

Ionic bond

Essential Chemistry for Biology: Study Notes

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