Question 1

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

Accepted Answer

Hydrogen bonds in ice cause water molecules to be less densely packed than in liquid water.

Question 2

A nitrogen atom has 7 protons and its most common isotope has 7 neutrons. What is the atomic number and mass number of a radioactive isotope of nitrogen with 9 neutrons?

Accepted Answer

Atomic number: 7, Mass number: 16

Question 3

Which of the following statements about covalent bonds is correct?

Accepted Answer

Covalent bonds involve the sharing of electrons between atoms.

Question 4

Why does water have a high surface tension compared to most other liquids?

Accepted Answer

Because of the cohesive forces due to hydrogen bonding between water molecules.

Question 5

Which of the following best describes a buffer in a biological system?

Accepted Answer

A buffer minimizes changes in pH by accepting or donating hydrogen ions.

Question 6

What is the main reason that water is called the 'solvent of life'?

Accepted Answer

Water's polarity allows it to dissolve many ionic and polar substances.

Question 7

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

Accepted Answer

Decreased carbonate ion concentration, making it harder for corals to build skeletons.

Question 8

Which of the following best describes the difference between an ionic bond and a covalent bond?

Accepted Answer

Ionic bonds involve the transfer of electrons, while covalent bonds involve the sharing of electrons.

Question 9

A scientist is studying the effect of carbonate ion concentration on the rate of calcium deposition by coral reef organisms. In this experiment, what is the independent variable?

Accepted Answer

The concentration of carbonate ions

Question 10

Which of the following equations correctly represents the chemical reaction that occurs when carbon dioxide dissolves in water and leads to ocean acidification?

Accepted Answer

$$CO_2 + H_2O$$ \rightarrow H_2CO_3$$

Question 11

Which property of water allows it to moderate Earth's climate and maintain stable temperatures in organisms?

Accepted Answer

Water's high specific heat due to hydrogen bonding

Question 12

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

Accepted Answer

Sweat absorbs heat as it evaporates, removing thermal energy from the skin.

Question 13

Which of the following is a trace element commonly added to municipal water supplies to prevent disease?

Accepted Answer

Fluoride

Question 14

Which of the following best describes a polar covalent bond?

Accepted Answer

Electrons are shared unequally, resulting in partial charges on the atoms.

Question 15

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 16

Which of the following best explains why salt (NaCl) dissolves easily in water?

Accepted Answer

The positive and negative ends of water molecules surround and separate the Na+ and Cl- ions.

Question 17

Which of the following is a direct result of the cohesion of water molecules?

Accepted Answer

The formation of water droplets on a surface

Question 18

Which of the following best describes the role of hydrogen bonds in the structure of water?

Accepted Answer

Hydrogen bonds hold water molecules together, giving water its unique properties.

Question 19

Which of the following statements about chemical reactions is correct?

Accepted Answer

Chemical reactions rearrange existing atoms to form new substances.

Question 20

Which of the following best explains why coral reefs are threatened by increased atmospheric $$CO_2$$?

Accepted Answer

Increased $$CO_2$$ lowers ocean pH, reducing carbonate ion availability for coral skeleton formation.

The Chemical Basis of Life: Elements, Atoms, and Compounds

Guida di studio - Domande di pratica

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