$$\text{Atomic Mass} = \text{Number of Protons} + \text{Number of Neutrons}$$

Question 1

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

Accepted Answer

An element cannot be broken down into other substances by chemical reactions; a compound contains two or more elements in a fixed ratio.

Question 2

Which group of elements makes up the majority of living matter as key structural building blocks?

Accepted Answer

C, H, O, N

Question 3

A glass of water with dissolved table salt (NaCl) is an example of which of the following?

Accepted Answer

A mixture

Question 4

Which of the following statements about atoms is correct?

Accepted Answer

Atoms are the smallest unit of matter that retain the properties of an element.

Question 5

Which subatomic particle has a negative charge and contributes negligible mass compared to a proton or neutron?

Accepted Answer

Electron

Question 6

An atom's atomic mass is the sum of which two quantities?

Accepted Answer

Protons and neutrons

Question 7

Which electrons primarily determine an atom's chemical behavior?

Accepted Answer

Valence electrons (outermost orbital)

Question 8

Two atoms of the same element that differ only in their number of neutrons are called:

Accepted Answer

Isotopes

Question 9

An atom that has gained electrons and now carries a negative charge is called a(n):

Accepted Answer

Anion

Question 10

Which type of radioactive decay is stopped by a sheet of paper and involves the loss of 2 protons and 2 neutrons?

Accepted Answer

Alpha decay

Question 11

A hospital uses a radioactive glucose tracer to visualize tissue activity in a PET scan. Which property of radioactive isotopes makes this possible?

Accepted Answer

They emit energy and particles as their nuclei decay, which can be detected by imaging equipment.

Question 12

Which of the following best explains why carbon-14 is useful for dating ancient biological materials but not for dating rocks billions of years old?

Accepted Answer

Carbon-14 has a relatively short half-life, making it suitable for dating materials up to about 50,000 years old.

Question 13

What is the key difference between a covalent bond and an ionic bond?

Accepted Answer

Covalent bonds involve sharing a pair of valence electrons; ionic bonds involve attraction between a cation and an anion.

Question 14

Which of the following best describes the role of hydrogen bonds in biological molecules?

Accepted Answer

They are weak bonds that help stabilize the structure of DNA and proteins.

Question 15

Which of the following statements about chemical equilibrium is correct?

Accepted Answer

The forward and reverse reactions occur at the same rate, so overall concentrations stay constant.

Question 16

A cold pack used for sports injuries absorbs heat from its surroundings when activated. Which type of reaction is occurring inside the pack?

Accepted Answer

Endothermic reaction

Question 17

Which of the following best explains why water (H$$_2O) $$has properties different from its component elements hydrogen and oxygen?

Accepted Answer

Water is a compound with emergent properties that differ from those of hydrogen and oxygen.

Question 18

Which of the following equations correctly represents the calculation of atomic mass?

Accepted Answer

$$	ext{Atomic Mass} = 	ext{Number of Protons} + 	ext{Number of Neutrons}$$

Question 19

Which of the following best describes the energy stored in chemical bonds?

Accepted Answer

It is released when bonds are broken, and the stronger the bond, the more energy is released.

Question 20

A scientist is studying a molecule with the formula C$$_6H$_{12}O$_6. $$Which of the following statements is true about this substance?

Accepted Answer

It is a compound because it contains more than one element in a fixed ratio.

The Chemical Context of Life: Atoms, Elements, and Chemical Bonds

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