Chemistry Outline Notes

Question 1

What is a chemical reaction? (Definition and examples)

Answer 1

A molecular change of matter that is not always reversible and in which something new is being produced. Ex: Burning gas in a car, taking a tums, a nail rusting.

Question 2

What is a physical change? (Definition and examples)

Answer 2

A change in the state of matter, usually reversible. Ex: painting a fence, making a milkshake, making a popsicle.

Question 3

Definition of matter and the two types of changes.

Answer 3

Anything that takes up space. The two types of changes are physical and chemical.

Question 4

What is all matter composed of? What are the three parts to this?

Answer 4

Atoms. The three parts: protons, neutrons, and electrons.`

Question 5

What is the nucleus? What are the charges and weight of the particles that make up the nucleus?

Answer 5

The nucleus is the center of an atom, containing positively charged protons and neutrally charged neutrons, each weighing about 1 amu (atomic mass unit).

Question 6

Electrons: weight, charge, etc.

Answer 6

Electrons are negatively charged and weigh almost nothing- about 1/1000 of an amu. Electrons take up the most space of any atomic particle.

Question 7

What do electrons orbit in?

Answer 7

Energy levels, aka electron clouds or orbitals.

Question 8

How many electrons can the first energy level hold? The second? The third?

Answer 8

1st: 2. 2nd: 8. 3rd: 18, but it is electrically stable with 8.

Question 9

Atomic number

Answer 9

The number of protons. This can also be used to determine the number of electrons, because a regular atom with a neutral charge has an equal number of protons and electrons. The atomic number is unique for every element.

Question 10

Atomic mass number

Answer 10

Number of protons+number of neutrons. It indicates how much mass the atom has.

Question 11

CHNOPS

Answer 11

Carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur. These naturally occurring elements are essential for life.

Question 12

If H (hydrogen) weighs 1 amu and has 1 proton, how many neutrons does it have?

Answer 12

0.

Question 13

All naturally occurring elements are____ in charge.

Answer 13

Neutral. This is why the number of protons would equal the number of electrons.

Question 14

What are isotopes and what can they be used for?

Answer 14

They are atoms that differ in their number of neutrons. They are unstable and can release small amounts of energy in the form of radiation. We can use them to date fossils and in medicine as tracers.

Question 15

Valence electrons

Answer 15

Electrons on the outermost energy level. When drawing a molecule, it is only necessary to include the outermost energy level. Atoms chemically react to fill their outermost shell and therefore become stable.

Question 16

Is hydrogen stable? Why or why not?

Answer 16

It is not stable because its outermost ring can hold 2 electrons but only has one. It wants to gain one more electron.

Question 17

Atoms join to become stable. What is it called when 2 or more atoms join together?

Answer 17

Molecules.

Question 18

What forms when atoms join to keep them together?

Answer 18

Chemical bonds.

Question 19

How does hydrogen gas form?

Answer 19

2 hydrogen molecules want their outermost ring to be full, so they both want to gain one more valence electron. They share electrons.

Question 20

The bond in which electrons are shared?

Answer 20

Covalent bond.

Question 21

The bond in which electrons are moved or taken?

Answer 21

Ionic bond. The connection is formed because the atom that gives away its electron now has a positive charge, and the atom that gains an electron has a negative charge. The opposite charges attract.

Question 22

What does the law of conservation of mass and energy state?

Answer 22

Mass and energy are neither created or destroyed, they just change form.

Question 23

How many molecules are there in 3 NaCl? How many Na atoms and Cl atoms are there?

Answer 23

3 molecules of NaCl (sodium chloride: table salt), 3 atoms of Na and 3 atoms of Cl.

Question 24

2 H2 +O—> 2H2O. Explain this and whether it follows the law of conservation.

Answer 24

Two molecules of hydrogen gas (four atoms total of hydrogen) plus one oxygen atom equals two molecules of water-four hydrogen atoms and TWO oxygen atoms. The law is not followed because the total amount of atoms changes- you would need another oxygen atom in the reactant (totaling 2) to get the two oxygen atoms in the product.

Question 25

How should you write a chemical equation?

Answer 25

Reactants—>products.

Question 26

How many naturally-occurring elements are there?

Answer 26

92.

Question 27

2 H2 +O—> 2H2O. How would this be rewritten so that it does follow the law of conservation?

Answer 27

2H2 + O2 = 2H2O.

Question 28

A cell’s mass is mostly…

Answer 28

Water

Question 29

Some properties of water

Answer 29

It is a polar molecule, it forms hydrogen bonds, cohesion, adhesion, surface tension, it is a good solvent, it has a high heat capacity, and it expands when frozen.

Question 30

In a solution of saltwater, which is the solvent and which is the solute?

Answer 30

Water=solvent, salt=solute.

Question 31

A solute usually has the (greater/lesser) quantity in a solution than the solvent.

Answer 31

Lesser.

Question 32

How do you know when a molecule’s bond is ionic or covalent?

Answer 32

If the elements making up the molecule are both yellow, it is covalent. Green and green or green and yellow are ionic.

Question 33

What does it mean when a solution is saturated?

Answer 33

There are no more molecules of solvent available to surround any more molecules of solute.

Question 34

What is a hydrogen bond?

Answer 34

A bond formed between molecules of water because of hydrogen atoms’ positive charge and oxygen atom’s negative charge. Opposite charges attract.

Question 35

What does a hydrogen bond allow water to do?

Answer 35

It allows for capillary action in which water sticks to the sides of its container and to itself; in this way it can allow trees to get water all the way from their roots to the tops of their trunks.

Question 36

What does it mean that water has a high heat capacity?

Answer 36

It takes a lot of energy to heat up or cool down water, unlike metal and diamond.

Question 37

What does water do when frozen? Why is this unusual?

Answer 37

It expands. Most substances become denser when frozen.

This is why ice floats.

Question 38

Why does water conduct electricity?

Answer 38

The ions in H2O make it conductive.

Question 39

Acids tend to be…in taste. Bases are usually…

Answer 39

Sour for acids, bitter for bases.

Question 40

What does pH stand for?

Answer 40

power of Hydrogen.

Question 41

Positive hydrogen ions make something more…

Answer 41

Acidic. 1-6 on pH scale.

Question 42

Negative hydroxide ions make something more…

Answer 42

Basic. 7-14 on pH scale.

Question 43

Deionization

Answer 43

Water can be forced through a resin to get rid of ions, in a lot of cases, like molecules of salt (NaCl). Deionized water is not as conductive as regular water, because the ions determine conductivity.

Question 44

Number of H and OH molecules in pure water?

Answer 44

Pure water has an equal number of hydrogen (+) and hydroxide (-) ions, meaning its charge is neutral. For a pH of 7 (neutral) hydrogen=110^(-7) and
hydroxide (OH)=110^(-7).

Question 45

Dissociation

Answer 45

The reaction in which water breaks into hydrogen and hydroxide ions is a dissociation reaction. When a molecular compound undergoes dissociation into ions, the reaction can also be called ionization.
H2O → H+ + OH-