CHEM Test 1
Popular Compound Names
B2H6 Diborane SiH4 Silane NH3 Ammonia PH3 Phosphine H20 Water H2S Hydrogen sulfide
Metalloids
Boron (B), Silicon (Si), Germanium (Ge), Arsenic (As), Antimony (Sb), Tellurium (Te), Polonium (Po), Astatine (At)
Homonuclear diatomic molecules
Both atoms in each molecule are of the same element. Ex: H2, N2, and O2
Some Compounds Named Using Greek Prefixes
CO Carbon Monoxide CO2 Carbon Dioxide SO2 Sulfur Dioxide SO3 Sulfur Trioxide NO2 Nitrogen Dioxide N2O5 Dinitrogen Pentoxide
Group 6A
Chalcogens
Burning wood in a fireplace is a __________ change.
Chemical
Identify this process as a physical or chemical change: Bacteria converts milk to yogurt
Chemical
Nucleus
Quantity center/core of an atom contains protons and neutrons
Physical Change
One in which the state of matter changes, but the identity of the matter does not change. Ex: Melting point, boiling point, freezing point
Chemical Property
One that can be observed and measured by changing the identity of a substance.
Physical property
One that can be observed and measured without changing the identity of a substance.
Melting is a __________ change
Physical
Experiment
Procedure to test hypothesis; measures one variable at a time
Rules for naming acids:
Remove ending of element, Change -ide to end of second element to -ic, Combine two words, Add acid
Nonmetals
Right side
Model (Theory)
Set of conceptual assumptions that explains data from accumulated experiments; predicts related phenomena
Extensive property
The measured value depends on the amount of matter Ex: Mass, length, volume
Intensive property
The measured value does not depends on the amount of matter Ex: Density, temperature
Chemical formula
denotes the composition of the substance.
Heterogeneous mixture
does not have a uniform composition (distinct) Ex: sand and water, water and gasoline
Core electrons
electrons close to nucleus
Groups/Families
vertical columns in the periodic table Elements in the same group tend to have similar physical and chemical properties
Heteronuclear diatomic molecules
A diatomic molecule can also contain atoms of different elements Ex: HCl, H20
Conversion Factor
A fraction in which the same quantity is expressed one way in the numerator and another way in the denominator Conversion factor are equal to 1
Explain the difference between a hypothesis and a theory.
A hypothesis is a tentative explanation for observations made and a theory is a unifying principle that explains a body of experimental observations and the laws that are based on them.
Briefly explain the relationship between hypothesis and experiment in the scientific method.
A hypothesis should be capable of leading to a prediction which is testable by experiment. If the experimental result differs from the prediction, the hypothesis should be modified.
Hypothesis
A tentative explanation that explains observations
Group 8A
Noble/Inert gases
Qualitative
Not requiring explicit measurement a physical property
Inexact numbers
Numbers measured by any method other than counting
Chemical Change
One in which the state of matter changes, and the identity of the matter changes. After a chemical change, the original substance (hydrogen gas in this case) will no longer exist. You get a different substance Ex: combustion
Three physical states
solid, liquid, and gas
Significant Figures in Addition and Subtraction
the answer cannot have more digits to the right of the decimal point than the original number with the smallest number of digits to the right of the decimal point.
Significant Figures in Multiplication and Division
the number of significant figures in the final product or quotient is determined by the original number that has the smallest number of significant figures.
Discuss the difference between the Celsius and Fahrenheit scale for measuring temperatures.
0°C = 32°F and 100°C = 212°F. To convert from °F to °C use the equation °C = (°F -32°F) x 5°C/9°F and to convert from °C to °F use the equation °F = [9°F/5°C](°C) + 32°F
Transition Metals
3B-2B
Group 1A
Alkali Metals (Hydrogen don't count)
Group 2A
Alkaline earth metals
Dimensional Analysis
Also called the factor-label method The use of conversion factors in problem solving
Significant figures Rules
Any digit that is not zero is significant (112.1 has four significant figures). Zeros located between nonzero digits are significant (305 has three significant figures, and 50.08 has four significant figures). Zeros to the left of the first nonzero digit are not significant (0.0023 has two significant figures, and 0.000001 has one significant figure). Zeros to the right of the last nonzero digit are significant if the number contains a decimal point (1.200 has four significant figures Zeros to the right of the last nonzero digit in a number that does not contain a decimal point may or may not be significant (100 may have one, two, or three significant figures—it is impossible to tell without additional information. To avoid ambiguity in such cases, it is best to express such numbers using scientific notation Ex: 1.3 × 10^2 two significant figures 1.30 × 10^2 three significant figures
Significant figures
Are the meaningful digits in a reported number.
Valence electrons
Electrons far away from nucleus and in outermost shell Roman numeral numbers indicates its valence electrons
Dalton's Atomic Theory
Elements are composed of extremely small particles called atoms. All atoms of a given element are identical, having the same size, mass, and chemical properties. The atoms of one element are different from the atoms of all other elements. Compounds are composed of atoms of more than one element. In any given compound, the same types of atoms are always present in the same relative numbers. A chemical reaction rearranges atoms in chemical compounds; it does not create or destroy them.
Group 7A
Halogens
A dip of vanilla ice cream is a pure substance.
False
Boiling point and melting point are extensive properties
False
Rusting of a piece of iron under environmental conditions is a physical change.
False
The ripening of fruit, once picked, is an example of physical change
False
When applying the scientific method, it is important to avoid any form of hypothesis
False
Periods
Horizontal rows in the periodic table
Exact numbers
Include numbers with defined values such as: 2.54 in the definition 1 inch (in) = 2.54 cm 1000 in the definition 1 kg = 1000 g 12 in the definition 1 dozen = 12 objects
Atomic mass
Is the mass of an atom in atomic mass units
Neutrons
Neutral charge particles in the nucleus 0
Temperature equations
K= °C +273.15 Temp in Celsius = (temp in F - 32°F) X (5°C/9°F) Temp in Fahrenheit = (9°F/5°C) X (temp in C) + 32°F
Metals
Left side
Base SI Units
Length= meter = m Mass= Kilogram = kg Time= second = s Electric current= ampere = A Temperature= kelvin = K Amount of substance= mole = mol Luminous intensity= candela = cd
Quantitative
Measured and expressed with a number a physical property
Elements are categorized as
Metals, nonmetals, metalloids
Greek Prefixes
Mono- 1 Di- 2 Tri- 3 Tetra- 4 Penta- 5 Hexa- 6 Hepta- 7 Octa- 8 Nona- 9 Deca- 10
Observation
Natural phenomena and measured events; if universally consistent can be stated as a law
Electrons
Negatively charged particles in the orbits around the nucleus -1
Accuracy
Tells us how close a measurement is to the true value
Precision
Tells us how close multiple measurements of the same thing are to one another
Prefixes Used with SI Units
Tera- T = 1 x 10^12 Giga- G = 1 x 10^9 Mega- M = 1 x 10^6 Kilo- k = 1 x 10^3 Deci- d = 1 x 10^-1 Centi- c = 1 x 10^-2 Milli- m = 1 x 10^-3 Micro- μ = 1 x 10^-6 Nano- n = 1 x 10^-9 Pico- p = 1 x 10^-12
Further Experiment
Tests predictions based on model
Temperature
The Celsius scale was originally defined using the freezing point (0°C) and the boiling point (100°C) of pure water at sea level. The SI base unit of temperature is the kelvin. Kelvin is known as the absolute temperature scale, meaning that the lowest temperature possible is 0 K, a temperature referred to as "absolute zero."
Proust's law of definite proportions :
The law that describes different samples of a given compound that always contain the same elements in the same mass ratio
Protons
The positively charged particles in the nucleus +1
The density of a substance is an intensive property.
True
The juice from an orange is a mixture.
True
The number 6.0448, rounded to 3 decimal places, becomes 6.045.
True
When applying the scientific method, a model or theory should be based on experimental data.
True
Diatomic molecule
When a molecule contains two atoms Ex: H2O, H2, N2, O2, Cl2, F2, I2, Br2
The law of multiple proportions
When two elements (call them A and B) form two different compounds, the masses of element B that combine with 1 g of element A can be expressed as a ratio of small whole numbers.
Isotopes
atoms that have the same atomic number (Z) but different mass numbers (A).
Binary molecular compounds
consist of just two different elements. To name such a compound, we first name the element that appears first in the formula. We then name the second element, changing the ending of its name to -ide. HCl hydrogen chloride SiC silicon carbide
Homogeneous mixture
has a uniform composition throughout (dissolve) Ex: sugar and water, starch and water
Metalloid
has properties that are intermediate between those of metals and nonmetals
Molecule
is a combination of at least two atoms in a specific arrangement held together by electrostatic forces known as covalent chemical bonds
Mixture
is a combination of two or more substances in which the substances retain their distinct identities. mixtures can be solids, liquids, or gases two types: homogeneous and heterogeneous
Substance
is a form of matter that has a definite (constant) composition and distinct properties. Ex: sodium chloride, iron, water, mercury, carbon dioxide, and oxygen. categorized as either an element or a compound.
Metal
is a good conductor of heat and electricity Ex: Sodium
Mass
is a measure of the amount of matter in an object or sample. 1kg= 1000g = 1 x 10^3 g
Compound
is a substance composed of atoms of two or more elements chemically united in fixed proportions. A compound cannot be separated into simpler substances by any physical process.
Element
is a substance that cannot be separated into simpler substances by chemical means.
Acids
is a substance that produces hydrogen ions (H+) when dissolved in water. Several binary molecular compounds produce hydrogen ions when dissolved in water and are, therefore, acids. In these cases, two different names can be assigned to the same chemical formula Ex: . HCl, hydrogen chloride, is a gaseous compound. When it is dissolved in water, however, we call it hydrochloric acid.
Matter
is anything that has mass and occupies space.
One atomic mass unit (amu)
is defined as a mass exactly equal to one-twelfth the mass of one carbon-12 atom.
Allotrope
is one of two or more distinct forms of an element. Two of the allotropic forms of the element carbon—diamond and graphite—have dramatically different properties.
Atomic weight
is sometimes used to mean average atomic mass. The atomic masses in the periodic table are average atomic masses.
Atomic Number (Z)
is the number of protons in the nucleus of each atom of an element.
Chemistry
is the study of matter and the changes that matter undergoes.
Mass Number (A)
is the total number of neutrons and protons present in the nucleus of an atom of an element. mass number (A) = number of protons (Z) + number of neutrons
Nonmetal
is usually a poor conductor of heat and electricity.
The derived SI unit for volume
meter cubed (m^3)
Density
ratio of mass to volume. d = m/v OR m = vd OR v = m/d 1 g/cm^3 = 1 g/mL = 1000 kg/m^3 1 g/L = 0.001 g/mL
Liquids and gases
referred to collectively as fluids.
Solids and liquids
referred to collectively as the condensed phases.
Structural formula
shows not only the elemental composition, but also the general arrangement of atoms within the molecule.
Molecular formula
shows the exact number of atoms of each element in a molecule