Question 1

Which of the following best describes a compound?

Accepted Answer

A substance formed by two or more different elements combined in a fixed ratio.

Question 2

Which subatomic particle is responsible for the chemical bonding between atoms?

Accepted Answer

Electron

Question 3

What is the main reason water is essential for life at the cellular level?

Accepted Answer

Water acts as a solvent, allowing chemical reactions to occur within cells.

Question 4

Which of the following statements about elements is correct?

Accepted Answer

Elements are composed of only one type of atom.

Question 5

If a cell is composed of 10.95% water by mass, what is the mass of water in a cell that weighs 200 g?

Accepted Answer

$$0.1095 	imes 200 = 21.9 g$$

Question 6

Which property of water allows it to dissolve many substances, making it an effective solvent in biological systems?

Accepted Answer

Water is a polar molecule.

Question 7

Which of the following best explains why atoms of different elements have different chemical properties?

Accepted Answer

They have different numbers of electrons in their outer shells.

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 hydrogen ions.

Question 9

Which of the following is a correct definition of a buffer in biological systems?

Accepted Answer

A buffer is a substance that resists changes in pH when acids or bases are added.

Question 10

Which of the following is NOT a property of acids?

Accepted Answer

Acids increase the concentration of hydroxide ions ($$[OH^-]) in $$solution.

Question 11

Which of the following best describes a hydrogen bond?

Accepted Answer

A bond formed between a hydrogen atom and a highly electronegative atom such as oxygen or nitrogen.

Question 12

Which of the following molecules is held together by ionic bonds?

Accepted Answer

NaCl

Question 13

A student mixes salt (NaCl) in water. What type of interaction occurs between the Na$$^+$$ and Cl$$^-$$ ions and water molecules?

Accepted Answer

Hydration shell formation

Question 14

Which of the following statements about cell composition is correct?

Accepted Answer

Most living matter is made of four main elements: C, O, N, H.

Question 15

Which of the following is the smallest unit of matter that retains the properties of an element?

Accepted Answer

Atom

Question 16

Which of the following best explains why water has a high surface tension?

Accepted Answer

Water molecules form hydrogen bonds with each other.

Question 17

Which of the following is a correct statement about the pH scale?

Accepted Answer

A solution with pH 7 is neutral.

Question 18

Which of the following is a real-world example of a buffer system in the human body?

Accepted Answer

The bicarbonate buffer system in blood

Question 19

Which of the following best describes the relationship between atoms, molecules, and compounds in biological systems?

Accepted Answer

Atoms combine to form molecules, and compounds are formed by combinations of different elements in fixed ratios.

Question 20

Which equation correctly represents the relationship between meter, millimeter, micrometer, and nanometer?

Accepted Answer

$$1 	ext{ m} = 1000 	ext{ mm} = 1,000,000 	ext{ \mu m} = 1,000,000,000 	ext{ nm}$$

Atoms, Molecules, and Water: Foundations of Cell Composition and Chemical Bonds

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