Unit 1

Question 1

What is a chemical element?

Answer 1

A substance that cannot be created or broken down by ordinary chemical means.

Question 2

List the four most common chemical elements in the body.

Answer 2

• Oxygen (O)
• Carbon (C)
• Hydrogen (H)
• Nitrogen (N)

Question 3

Define the term ‘atom’.

Answer 3

The smallest unit of an element.

Question 4

What are the three subatomic particles that make up an atom?

Answer 4

• Protons
• Neutrons
• Electrons

Question 5

What charge does a proton have?

Answer 5

Positive charge.

Question 6

What charge does a neutron have?

Answer 6

No electrical charge.

Question 7

What charge does an electron have?

Answer 7

Negative charge.

Question 8

What is a molecule?

Answer 8

Two or more atoms covalently bonded together.

Question 9

What is a compound?

Answer 9

A substance composed of two or more different elements joined by chemical bonds.

Question 10

How is an ion formed?

Answer 10

By donating or accepting electrons to achieve a full valence shell.

Question 11

What is an ionic bond?

Answer 11

A bond formed between cations and anions due to their opposite charges.

Question 12

How is a covalent bond formed?

Answer 12

By sharing electrons between atoms to fill their valence shells.

Question 13

What distinguishes organic molecules from inorganic molecules?

Answer 13

Organic molecules contain both carbon and hydrogen, while inorganic molecules do not.

Question 14

What are two characteristics of organic molecules that make them useful to living organisms?

Answer 14

• They can form complex structures.
• They can store and transfer energy.

Question 15

What are the chemical properties of water?

Answer 15

Water is a polar molecule, has a high specific heat, and is an excellent solvent.

Question 16

What is the atomic number of an element?

Answer 16

The number of protons in the nucleus of an atom.

Question 17

What is the mass number of an element?

Answer 17

The sum of protons and neutrons in the nucleus.

Question 18

Fill in the blank: A complete _______ shell makes an atom non-reactive.

Answer 18

valence

Question 19

What is a cation?

Answer 19

An ion with a positive charge formed by donating electrons.

Question 20

What is an anion?

Answer 20

An ion with a negative charge formed by accepting electrons.

Question 21

What is a polar covalent bond?

Answer 21

A bond with unequal sharing of electrons, resulting in partial charges.

Question 22

True or False: Water (H2O) is classified as an inorganic compound.

Answer 22

True

Question 23

True or False: Carbon dioxide (CO2) is both a molecule and a compound.

Answer 23

True

Question 24

Fill in the blank: When you break covalent bonds, you release _______.

Answer 24

energy

Question 25

What is a hydrogen bond?

Answer 25

A weak attraction between a slightly positive hydrogen atom and an electronegative atom from another molecule.

Question 26

What defines a nonpolar covalent bond?

Answer 26

Balanced, equal sharing of electrons.

Question 27

What is a dipole?

Answer 27

A molecule that has a partial positive charge on one side and a partial negative charge on the other side ## Footnote Dipoles occur due to differences in electronegativity between atoms in a molecule.

Question 28

What is a hydrogen bond?

Answer 28

A weak attraction between a weakly positive hydrogen atom and an electronegative atom from another molecule ## Footnote Hydrogen bonds are represented by dotted lines due to their relative weakness.

Question 29

What causes hydrogen bonds to form in water molecules?

Answer 29

The slightly positive charge on hydrogen atoms interacts with the slightly negative charge on oxygen atoms ## Footnote This interaction leads to the unique properties of water.

Question 30

Why can a water strider stand on water?

Answer 30

Because of its light weight and the surface tension of water ## Footnote Surface tension is a result of hydrogen bonding between water molecules.

Question 31

What is a dipole-ion bond?

Answer 31

An interaction where the partial charges on water molecules pull apart ionic compounds like NaCl ## Footnote The weakly positive portion of water interacts with Cl- and the weakly negative portion interacts with Na+.

Question 32

How do dipole charges affect nonpolar covalent bonds?

Answer 32

They repel nonpolar molecules such as fats, lipids, and oils ## Footnote This is due to the lack of partial charges in nonpolar molecules.

Question 33

What type of bond is formed between H+ and Cl- in hydrochloric acid?

Answer 33

Ionic bond ## Footnote Ionic bonds occur when electrons are transferred between atoms, resulting in charged ions.

Question 34

Fill in the blank: The weakly positive portion of water interacts with the _______ anion.

Answer 34

Cl- ## Footnote This interaction is part of the dipole-ion bonding process.

Question 35

Fill in the blank: The weakly negative portion of water interacts with the _______ cation.

Answer 35

Na+ ## Footnote This interaction helps to dissolve ionic compounds in water.

Question 36

True or False: Hydrogen bonds are stronger than covalent bonds.

Answer 36

False ## Footnote Hydrogen bonds are relatively weak compared to covalent bonds.