chapter 2

Question 1

Organisms are chemical machines. What is chemistry the science of?

Answer 1

Chemistry is the science of change.

Question 2

What is any substance in the universe that has mass and occupies space is comprised of ?

Answer 2

Any substance in the universe that has mass and occupies space is comprised of matter. All matter is made up of atoms.

Question 3

All atoms have the same structure. What is it?

Answer 3

At the core is a dense nucleus comprised of two subatomic particles
protons (positively charged) 1 mass unit
neutrons (no associated charge) 1 mass unit
Orbiting the nucleus is another cloud of subatomic particles, electrons, which are negatively charged and have low mass unit.

Question 4

atomic number formula

Answer 4

Atomic number = number of electrons = number of protons

Question 5

atomic mass/mass number formula

Answer 5

Atomic mass/mass number=number of protons and number of neutrons

Question 6

define atomic number

Answer 6

The number of protons in the nucleus.

Atoms with the same atomic number exhibit the same chemical properties and are considered to belong to the same element

Question 7

define atomic mass

Answer 7

The number of protons plus neutrons in the nucleus.

Electrons have negligible mass.

Question 8

Which subatomic particle determines the chemical behavior of atoms?

Answer 8

Electrons determine the chemical behavior of atoms, Electrons have energy of position, called potential energy

Question 9

What are orbitals?

Answer 9

electron shells, of an atom, are actually complex, three-dimensional volumes of space called orbitals.

Question 10

How many electrons can each level of orbital hold?

Answer 10

First shell can only hold 2, Second shell can only hold 8, Third shell can hold 8, and so on. Atoms that have incomplete electron orbitals tend to be more reactive

Question 11

What happens when electrons move to different energy levels?

Answer 11

As electrons move to a lower energy level, closer to the nucleus, energy is released.
Moving electrons to energy levels farther out from the nucleus requires energy.

Question 12

What are ions?

Answer 12

atoms that have gained or lost one or more electrons

Question 13

What are isotopes?

Answer 13

atoms that have the same number of protons but different numbers of neutrons. Most elements in nature exist as mixtures of different isotopes.

Question 14

What is radioactive decay?

Answer 14

Some isotopes are unstable and break up into particles with lower atomic numbers.

Question 15

What are the uses of radioactive isotopes?

Answer 15

Dating fossils and Medical procedures. Short-lived isotopes decay rapidly and do not harm the body and can be used as tracers in medical diagnoses and studies

Question 16

What is a molecule?

Answer 16

a group of atoms held together by energy in the form of a chemical bond.

Question 17

What are the three principal types of chemical bonds?

Answer 17

ionic, covalent, hydrogen

Question 18

What does the “co” in covalent mean?

Answer 18

“Co” means share

Question 19

What are Van der Waals forces?

Answer 19

Van der Waals forces are a kind of weak chemical attraction (not a bond) that come into play when atoms are very close to each other

Question 20

What is an ionic bond?

Answer 20

In an ionic bond, the metal will lose it’s end of the rope to the nonmetal. The “loser” is the metal and the “winner” is the nonmetal. The metal loses electrons to a nonmetal.

Question 21

Is Ice less dense than water?

Answer 21

Yes, ice is less dense than water.

Question 22

What is an example of an ionic bond?

Answer 22

NaCl is an example of an this bond.

Question 23

Molecules formed by an ionic bond are often as stable as?

Answer 23

Molecules comprised of these bonds are often stable as crystals. Crystals are defined as a solid state in which atoms are packed together tightly. The distinguishing feature of crystals is that their solid form is symmetrical on all sides.

Question 24

Does crystal formation occur in covalent bonds?

Answer 24

Yes, electrons jump out of the shell in the ionic bond.

Question 25

When do covalent bonds form?

Answer 25

Covalent bonds is when the electronegativity of two bonding atoms is very similar, neither atom wins the “tug of war” and the electrons are shared equally. Covalent bonds form between two atoms when they share electrons

Question 26

What is the difference between covalent and ionic bonds?

Answer 26

Covalent bonds are stronger than ionic bonds and are directional

Question 27

What is an example of a covalent bond?

Answer 27

H2 (Hydrogen gas)

Question 28

What are the two types of covalent bonds?

Answer 28

Polar (one is bigger) and Nonpolar (same size)

Question 29

How are polar covalent bonds formed?

Answer 29

Some atoms may be better at attracting the shared electrons of a covalent bond. This creates tiny partial negative and positive charges within the molecule, now called a polar molecule (there is a great electronegativity difference). Polar covalent bonds form when the shared electrons of a covalent bond spend more time in the vicinity of a particular atom.

Question 30

What are hydrogen bonds?

Answer 30

weak electrical attractions between the positive end of one polar molecule and the negative end of another. Water molecules can also form hydrogen bonds

Question 31

What is the difference in strength between bonds?

Answer 31

Covalent>Ionic>Hydrogen (CIH)

Question 32

What are the 7 unique properties of water?

Answer 32

Water is essential for life, a polar molecule, heat storage (water temperature changes slowly and holds temperature well), ice formation (water becomes less dense as it freezes because hydrogen bonds hold water molecules farther apart), High Heat of Vaporization (water requires tremendous energy to vaporize because hydrogen bonds must be broken), Water molecules are attracted to other polar molecules, and High polarity (In solution, water molecules tend to form the maximum number of hydrogen bonds.)

Question 33

What is adhesion?

Answer 33

when polar molecules other than water stick to a water molecule

Question 34

What is cohesion?

Answer 34

when one water molecule is attracted to another water molecule

Question 35

What does hydrophilic mean?

Answer 35

molecules are attracted to water and dissolve easily in it. These molecules are also polar and can form hydrogen bonds.

Question 36

What does hydrophobic mean?

Answer 36

molecules are repelled by water and do not dissolve. These molecules are nonpolar and do not form hydrogen bonds.

Question 37

What is pH?

Answer 37

The amount of ionized hydrogen from water in a solution can be measured as pH.

Question 38

The pH scale is logarithmic. What does this mean?

Answer 38

a pH scale difference of 1 unit actually represents a 10-fold change in hydrogen ion concentration. 1 pH unit=10 fold change in H concentration number

Question 39

What is the range of acidic and basic pH?

Answer 39

Basic>7
Neutral=7
Acidic<7