121 - Final Exam Flashcards
Define pure substance
A form of matter that always has a definite and constant composition
Define element
The simplest type of a substance with unique physical and chemical properties
Define molecule
A structure that consists of two or more atoms that are chemically (covalently) bonded together
Define compound
A substance composed of two or more elements which are chemically combined
How are an atom and molecule different?
Atoms are single units of substance, and molecules are the smallest stable unit.
Define chemical formula
Comprised of element symbols and numerical subscripts the type and number of each atom present
Define molecular formula
The true or actual number of atoms in the molecule
Define empirical formula
The simplest whole number ratio of the atoms
Define and give examples of physical properties
Properties that can be observed without changing the substance into another substance (color, density, conductivity, etc.)
Define and give examples of chemical properties
Properties that can only be observed by changing the substance into another substance (corrosiveness, flammability, etc)
Define intensive properties
Properties that are independent of the amount of substance
Define extensive properties
Properties that depend on the amount of substance being observed
What is the first law of thermodynamics?
Energy is neither created nor destroyed.
Who is the father of modern medicine?
German Paracelsus Theophrastus Bombastus von Hohenheim
What is the scientific method?
The process scientists use to explain observations in nature
What are the steps of the scientific method?
- Observation
- Generalizations / laws
- Hypotheses / theories
- Predictions based on theories
- Experimentation
Can theories be proven true?
No, only supported / rejected (contradicted)
What is temperature by definition?
A measure of the average kinetic energy of the particles in a sample
What is the conversion factor of F to C?
F = 9/5C + 32
What is heat?
A measure of the quantity of energy due to molecular motion
What is accuracy?
The proximity of a measurement to the “true” value of a quantity
What is precision?
The proximity of several measurements to each other
What is the law of conservation of mass?
The total mass of substances do not change in chemical reactions.
Who is the father of modern chemistry?
Antoine Lavoisier
What is the law of definite (or constant) composition?
The elemental composition of a pure substance is always the same. (First proposed by Joseph Proust)
What is the law of multiple proportions?
If elements A and B react to form more than one compound, the different masses of A that combined with a fixed mass of element B can be expressed as a ratio of small whole numbers.
Who discovered the electron?
J.J. Thompson w/ cathode rays
Who discovered the charge of electrons?
Robert Milikan w/ the oil drop experiment
What model of the atom did J.J. Thompson propose?
“Plum pudding model”
All electrons are embedded in the jelly-like sphere of positively charged electricity.
Who discovered radioactivity?
Henri Becquerel
Who named radioactivity?
Marie Curie
What is radioactivity?
The spontaneous emission of radiation by an atom.
Who discovered the nature of radioactive emissions?
Ernest Rutherford
Who discovered the nucleus?
Ernest Rutherford w/ the gold foil experiment
Who discovered protons?
Rutherford (he also predicted neutrons)
Who confirmed the presence of neutral particles in the nucleus?
James Chadwick
Which weighs more, protons or neutrons?
They have about the same mass.
Do electrons have mass?
Yes, but it’s so small we ignore it.
Who arranged the first periodic table?
Henry Moseley
What is an element’s atomic number?
The number of protons in the nucleus or the number of electrons in a neutral atom
What is an element’s mass number?
The total number of protons and neutrons in an atom’s nucleus
Which varies - the amount of protons or neutrons?
Neutrons (elements always have the same number of protons)
What are isotopes?
Atoms of the same element that have different number of neutrons and therefore different mass numbers
What are hydrates?
Molecules with a specific number of water molecules associated with each formula unit
Who is the father of the periodic table?
Mendeleev
What is the periodic law of the elements?
When elements are arranged in a particular order (increasing atomic number), elements of similar properties occur at periodic intervals
What are columns in a periodic table?
Groups
What are rows in a periodic table?
Periods
How do ionic bonds form?
Bonds formed by charge structure
How do covalent bonds form?
Bonds formed by shared electrons
What is the oxidation number for an element?
0
What is the oxidation number for a simple monatomic ion?
Equals its charge
What should the sum of all neutral molecules be?
0
What is H’s oxidation number?
1
What is O’x oxidation number?
-2 (except in peroxides where it is -1)
What is F’s oxidation number?
-1
What are the main points of Dalton’s atomic theory?
- Each element is composed of extremely small particles called atoms.
- All atoms of a given element are identical, but the atoms of one element are different from the atoms of all other elements.
- Atoms of one element cannot be changed into atoms of a different element by chemical reactions, and they are neither created nor destroyed in chemical reactions.
- Compounds are formed when atoms of more than one element combine, a given compound always has the same relative number and kind of atoms.
What is the charge of an electron?
1.602 x 10^-19
What are diatomic molecules?
Molecules made up of two atoms
What happens in combination reactions?
Two or more substances react to form one product
What happens in decomposition reaction?
A single reactant breaks apart to form two or more substances
What are combustion reactions?
Rapid reactions that produce a flame, typically involving oxygen
What is the formula weight of a compound?
The sum of the atomic weights (AW) of the atoms in the chemical formula of the substance
Also called the molecular weight
