Exam #1 Flashcards
Features of solids
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.
Features of liquids
has a varying shape that conforms to the container shape, but only to the extent of the liquid’s volume –> has an upper surface
Features of gas
has a varying shape that conforms to the container shape, but fills the entire container and does not have surface area.
Physical change
characteristics a substance shows by itself, without changing into or interacting with another substance
Chemical change
characteristics a substance shows as it changes into or interacts with another substance(s)
Combustion of a hydrocarbon
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.
Significant Figures
- 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
Sig Figs for arithmetic opperations
- 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
Precision
(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.
Accuracy
how close each measurement is to the actual value.
Accurate measurements have low systematic error and, generally, low random error.
Types of error
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.
Elements
- 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
Compounds
- 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.
Mixtures
- 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.
Pure Substance
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.
Mass Conservation Law
- 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).
Law of Definite Conservation
States, no matter what its source, a particular compound is composed of the same elements in the same parts (fractions) by mass.
Law of Multiple Proportions
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.
Dalton’s Atomic Theory
- 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).
Cathode Rays
- 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.
Plum Pudding Model
- 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.
Periodic Table Patterns
- 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.
Classifying Elements
- 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.
Ionic Bonding
- 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
Coulomb’s Law
- 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.
Binary Compounds
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.
Polyatomic Ions
- 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.
Acid Names from Anions
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:
