chemistry midterm Flashcards
element
the simplest form of matter that has a unique set of properties and cannot be broken down further
compound
a substance that contains two or more elements chemically combined in a fixed proportion
mixture
a physical blend of two or more components (i.e. 2+ elements, 2+ compounds, or element(s) + compound(s))
homogeneous mixtures
-uniform throughout
-must be in a single phase
-may seem like one thing
-can’t see the different substances
-can’t see the particles
-can be separated by physical means
heterogeneous mixtures
-not uniform throughout
-can be in more than one phase
-can see the different parts
-can be separated by physical means
why can mixtures be separated by physical means?
differences in physical properties can be used to separate components in a mixture
what are the ways that mixtures can be separated by physical means?
magnetism, evaporation/boiling, separation by hand, decanting or separation funnel, filtration, and distillation
magnetism
difference in magnetic properties (ex. iron + aluminum nails)
-IRON IS MAGNENTIC
evaporation/boiling
difference in boiling points (ex. salt water)
separation by hand
difference in color/physical appearance (ex. m&ms)
decanting or separation funnel
distinct layers due to different densities/polarities (ex. oil + water)
filtration
difference in particle size (ex. pepper + water)
distillation
differences in boiling points (ex. top water or window wiping fluid)
explain that compounds can only be separated into elements by chemical means
the elements within a compound are held together by chemical bonds, which can only be broken through a chemical reaction
give example of compounds being separated into elements by chemical means
water (H2O) which can be broken down into hydrogen and oxygen through electrolysis, mercuric oxide (HgO) which decomposes into mercury and oxygen when heated, and calcium carbonate (CaCO3) which can be separated into calcium oxide and carbon dioxide through thermal decomposition
intensive properties
properties that do not depend on the amount of matter
does not depend on amount but on TYPE
types of intensive properties
color, melting + boiling points, and density (mass/volume)
extensive properties
properties that depend on the AMOUNT of matter
types of extensive properties
mass, volume, and energy
physical properties
properties that can be observed or measured without changing the composition/identity of a substance (i.e. without performing a chemical reaction)
physical properties examples
color, mass, volume, melting/boiling point
chemical properties
properties that can only be observed by changing the composition/identity of
a substance (such as in a chemical reaction when atoms are rearranged, and new substances are
formed)
chemical properties examples
flammability, reactivity, toxicity, and acidity
physical change
a change that alters some property of the substance, such as form or appearance. the identity/composition of the substance remains the same. no new substance is formed.
two types of physical changes
irreversible and reversible
irreversible physical changes
breaking, tearing, cutting, grinding, etc
reversible physical changes
all phase changes
phase changes
drawing on notes
chemical changes
during a chemical reaction, a chemical change occurs, which changes the identify
of a substance
A NEW SUBSTANCE IS FORMED
indicators of a chemical change
change in color, transfer of energy (change in temp- hotter or colder; heat/fire, etc.), production of a gas (bubbling, fizzing, odor, sound), and formation of a precipitate (ppt)
state the law of conservation of matter during chemical reactions
mass cannot be created nor destroyed
-mass is always conserved during a chemical reaction
-total mass of the reactants must equal the total mass of the products
how do physical/chemical properties differ from physical/chemical changes?
properties: measured or observed characteristics (adjectives)
changes: alter physical properties or chemical identities (verbs)
BIG DIFFERENCE: DOES THE COMPOSITION CHANGE OR NOT?
3 types of subatomic particles
proton, electron, neutron
electric charge, symbol, location in atom, mass in grams, and mass number for proton
electric charge: 1+
symbol: p+
location: nucleus
mass in grams: 1.67 × 10^-24 g
mass number: 1
electric charge, symbol, location in atom, mass in grams, and mass number for electron
electric charge: 1-
symbol: e-
location: outside the nucleus/in the electron cloud
mass in grams: 9.12x 10^-28g
mass number: 0
electric charge, symbol, location in atom, mass in grams, and mass number for neutron
electric charge: 0
symbol: n^0
location in atom: nucleus
mass in grams 1.67x10^-24g
mass number: 1
how do you determine the number of each type of subatomic particle using the chemical symbol, isotope symbol, ion charge, and/or periodic table
use the element’s atomic number (found on the periodic table) to find the number of protons, which is then equal to the number of electrons in a neutral atom; the mass number (part of the isotope symbol) is used to calculate the number of neutrons by subtracting the atomic number from the mass number; and the ion charge indicates how many electrons have been gained or lost compared to a neutral atom
isotope
-isotopes of the same element have different mass numbers because they have different numbers of neutrons
-they show the same chemical properties because a difference in the number of neutrons makes no difference to how atoms react
how does an isotope occur
spontaneously through radioactive decay of a nucleus or artificially by bombarding a stable nucleus with charged particles via accelerators or neutrons in a nuclear reactor
two types of isotopes
stable isotopes and radioisotopes
stable isotopes
stability depends on the balance between the number of protons and neutrons
radioisotopes
isotopes that have unstable nuclei and become more stable through nuclear reactions
explain how the weighted average atomic mass of an element is determined
multiplying the relative abundance of each naturally occurring isotope of that element by its atomic mass, then adding up all those products; essentially, this means the more abundant an isotope is, the greater its contribution to the overall average atomic mass of the element
average atomic mass formula
(mass x %abundance)↓1 + (mass x %abundance)↓2 +…/100%
unit: amu or g
round to: the hundredths place
