Exam #1

Question 1

Features of solids

Answer 1

has a fixed shape that does not conform to the container shape. solids are not defined by rigidity or hardness –> solids can be hard or rigid, but they can also be flexible.

Question 2

Features of liquids

Answer 2

has a varying shape that conforms to the container shape, but only to the extent of the liquid’s volume –> has an upper surface

Question 3

Features of gas

Answer 3

has a varying shape that conforms to the container shape, but fills the entire container and does not have surface area.

Question 4

Physical change

Answer 4

characteristics a substance shows by itself, without changing into or interacting with another substance

Question 5

Chemical change

Answer 5

characteristics a substance shows as it changes into or interacts with another substance(s)

Question 6

Combustion of a hydrocarbon

Answer 6

The combustion reaction formula can be written with the hydrocarbon and oxygen on the left side; carbon dioxide and water on the right side. The energy released is also shown on the product side. For the combustion of methane.

Methane (Ex. Compound) + oxygen = Carbon dioxide + water + energy.

Question 7

Significant Figures

Answer 7

• All nonzero digits in a measurement are significant
  - 512 has three significant figures
• All zeros between nonzero digits are significant
  - 502 has three sig figs
• Leading zeros that occur before the first nonzero are not significant
  - 0.0055 has two sig figs
• Trailing zeros are significant if the measurement has a decimal point
  - 1.1300 had five sig figs
• Trailing zeros in a measurement without a decimal point are not
  significant, unless exponential notation clarifies the quantity
  - 5300 has two sig figs, 5.300 x 10^3 has four, 5.3 x 10^3 has two
• A terminal decimal point can also be used to indicate that trailing
  zeros are significant
  - 5300 has two, 5300. Has four

Question 8

Sig Figs for arithmetic opperations

Answer 8

• For multiplication and division
  - Your answer should have the same number of sig figs as the
  number with the fewest sig figs.
  - If I told you you have 3.4 mL and 340.87 g → your answer
  should include two sig figs.
• For addition and subtraction
  - The answer has the same number of decimal places as there are in
  the measurement with the fewest decimal places.
  - 83.5 mL → answer could look like 106.8 mL

Question 9

Precision

Answer 9

(reproducibility) refers to how close the measurements in a series are to each other.

Precise measurements have low random error, that is, small deviations from the average.

Question 10

Accuracy

Answer 10

how close each measurement is to the actual value.

Accurate measurements have low systematic error and, generally, low random error.

Question 11

Types of error

Answer 11

Systematic Error → produces values that are either all higher or all lower than the actual value. This type of error is part of the experimental system, often caused by a faulty device or by a consistent mistake in taking a recording.

Random Error → in the absence of systematic error, produces values that are higher and lower than the actual value. Random error always occurs, but its size depends on the measurer’s skill and the instrument’s precision.

Question 12

Elements

Answer 12

• the simplest type of matter with unique physical and chemical
  properties. It has features that include:
  - Only consists of one kind of atom, thus an element cannot be
  broken down into a simpler form of matter by physical or
  chemical methods.
  - Each element is unique because the properties of its atoms are
  unique.
  - In nature, most elements exist as populations of atoms, either
  separated or in contact with each other, depending on the physical
  state.
  - Several elements occur in molecular form, a molecule is an
  independent structure of two or more atoms bound together.
  - Ex. oxygen occurs in air as diatomic (two-atom-ed) → O2

Question 13

Compounds

Answer 13

• consist of two or more different elements that are bonded chemically
  (elements are not just mixed together, but their atoms have joined in
  a chemical reaction). They have major features which include:
  - Elements are present in compounds in fixed parts by mass (they
  have a fixed mass ratio). This is because each unit of the
  compound consists of a fixed number of atoms of each element.
  - Ex. Ammonia is 14 parts nitrogen by mass and 3 parts
  hydrogen by mass because 1 nitrogen atom has 14 times the
  mass of 1 hydrogen atom; and each ammonia molecule
  consists of 1 nitrogen atom and 3 hydrogen atoms.
  - A compound’s properties are different from the properties of its
  element.
  - A compound can be broken down into simpler substances – its
  component elements – via a chemical change.

Question 14

Mixtures

Answer 14

• consists of two or more substances that are physically intermingled,
  not chemically combined. Mixtures have defining features, such as:
  - Components of a mixture can vary in their parts by mass.
  - A mixture retains many of the properties of its components.
  - They can be separated into their components by physical
  changes, meaning chemical changes are not needed.

Question 15

Pure Substance

Answer 15

substances that are made up of only one kind of particle and have a fixed or constant structure. Pure substances are further classified as elements and compounds.

Question 16

Mass Conservation Law

Answer 16

• Stated by Lavoiseier
• States, the total mass of substances does not change during a
  chemical reaction
  - The number of substances may change, thus their properties
  must, as well, but the total amount of matter remains the same.
• Overall: mass conservation means that based on all chemical
  experience, matter cannot be created nor destroyed.
• Note: the mass before and the mass after sometimes may not be
  exactly the same because some mass can be converted into energy or
  vice versa (for example).

Question 17

Law of Definite Conservation

Answer 17

States, no matter what its source, a particular compound is composed of the same elements in the same parts (fractions) by mass.

Question 18

Law of Multiple Proportions

Answer 18

The law of multiple proportions says that when two elements combine with each other to form compounds, the masses of one of the elements which combine with fixed mass of other, bear a simple whole number ratio to one another. For e.g. consider CO and CO2. Both are compounds of carbon and oxygen.

Question 19

Dalton’s Atomic Theory

Answer 19

• All matter consists of atoms – tiny, indivisible units of an element that
  cannot be created nor destroyed (this is derived from the “eternal,
  indestructible atoms” proposed by Democritus and reflects the mass
  conservation law stated by Lavoiser).
• Atoms of one element cannot be converted to atoms of another
  element.
• Atoms of an element are identical in mass and other properties and
  are different from atoms of any other element (unique mass and
  properties for the atoms of a given element).
• Compounds result from the chemical combination of a specific ratio
  of atoms of different elements (this follows the law of definite
  composition).

Question 20

Cathode Rays

Answer 20

• To discover the nature of an electric current, investigators tried
  passing it through nearly evacuated glass tubes fitted with metal
  electrodes.
• When the electric power source was turned on, a ray could be seen
  striking the phosphor-coated end of the tube, which emitted a glowing
  sport of light. The rays were called cathode rays because they
  originated at the negative electrode (cathode) and moved to the
  positive electrode (anode).
• Cathode ray particles were later named electrons.
  - In a neon light sign, electrons collide with the gas particles in the
  tube, causing them to give off light.
  - The aurora borealis occurs when the Earth’s magnetic field bends
  streams of charged particles coming from the Sun, which then
  collide with gas particles in the atmosphere to give off light.

Question 21

Plum Pudding Model

Answer 21

• Thomson proposed the “plum-pudding model” (blueberry muffin
  model) → a spherical atom composed of diffuse, positively charged
  matter with electrons embedded in it like “raisins in a plum-pudding”
  (blueberries in a muffin).
• Ernest Rutherford tested this model and obtained a very unexpected
  result.

Question 22

Periodic Table Patterns

Answer 22

• The boxes are arranged into a grid of periods (horizontal rows) and groups
  (vertical columns) → each period is numbered 1-7 and each group is
  numbered 1-8 plus either the letter A or B.
• The eight A groups (two on the left and six on the right) contain the main-
  group elements. The ten B groups, located between Groups 2 A and 3 A
  contain
  the transition metals. The two horizontal series of inner transition metals
  contain the lanthanides and the actinides.

Question 23

Classifying Elements

Answer 23

• Metals (three shades of blue) → generally shiny solids at room temperature
• Nonmetals (yellow) → generally gasses or dull, brittle solids at room
  temperature.
• Metalloids (green) → also called semimetals, have properties between those of
  the metals and nonmetals.

Question 24

Ionic Bonding

Answer 24

• Ionic compounds are composed of ions, charged particles that form when an
  atom (or small group of atoms) gains or loses one or more electrons.
  - The simplest ionic compound is a binary ionic compound → one
  composed of ions of two elements It typically forms when a metal reacts
  with a nonmetal
  - Each metal atom loses one or more electrons and becomes a cation,
  a positively charged ion.
  - Each nonmetal atom gains one or more of the electrons lost by the
  metal atom and becomes an anion, a negatively charged ion.
• In effect, the metal atoms transfer electrons to the nonmetal atoms. The
  resulting large numbers of oppositely charged cations and anions attract each
  other by electrostatic forces and form the ionic compound.
  - A cation or an anion derived from a single atom is called a monatomic ion
  ** for a charge of 1+ or 1-, we just write the + or - in the superscript

Question 25

Coulomb’s Law

Answer 25

• The strength of the ionic bond depends to a great extent on the net
  strength of these attractions and repulsions and is described by this law.
  - Ions with higher charges attract (or repel) each other more strongly
  than do ions with lower charges.
  - Smaller ions attract (or repel) each other more strongly than do larger
  ions, because the chargers are closer to each other.

Question 26

Binary Compounds

Answer 26

a compound that is made exclusively of two different elements.

• For all ionic compounds, names and formulas give the positive ion (cation)
  first and the negative ion (anion) second
• For all binary ionic compounds the name of the cation is the name of the
  metal and the name of the anion has the suffix -ide.

Question 27

Polyatomic Ions

Answer 27

• The polyatomic ion stays together as a charged unit.
• Named like binary ionic compounds, with the exception that the name of
  the polyatomic ion is used without adding the suffix -ide; unless it already
  contains it (ex. hydroxide).
• Families of oxyanions
  - Most polyatomic ions are oxyanions → usually a nonmetal is bonded to
  one or more oxygen atoms.
  - Naming:
  - The ion with more O atoms takes the nonmetal root and the suffix
  -ate
  - The ion with fewer O atoms takes the nonmetal root and the suffix
  -ite.
  - **with four oxyanions in the family the very lowest ion has hypo in
  front and the very most has per in front.
• Hydrated ionic compounds
  - Ionic compounds called hydrates have a specific number of water
  molecules in each formula unit.

Question 28

Acid Names from Anions

Answer 28

When naming and writing their formulas we consider acids as anions that have one or more hydrogen ions (H+) added to give a neutral compound. The two common types of acids are binary acids and oxyacids: