Chapter 1-5 exam 1 for concepts of chemistry
A chemical formula - ANS - indicates all the elements present in a compound and
the relative number of atoms of each.
Here are some chemical formulas:
H2O
NH3
O2
H2SO4
\a Danish physicist, Niels Bohr came up with and atomic theory. - ANS - RULE 1:
Electrons can orbit only at certain allowed distances from the nucleus.
RULE 2: Atoms radiate energy when an electron jumps from a higher-energy orbit
to a lower-energy orbit. Also, an atom absorbs energy when an electron gets
boosted from a low-energy orbit to a high-energy orbit.
\A formula unit is the - ANS - smallest electrically neutral collection of ions.
Formula units are different from molecules in that they do not exist as discrete
(stand alone) molecules but instead exist as part of a larger lattice. Consider table
salt for example.
\Acetate - ANS - C2H3O2-
\Acids are - ANS - molecular compounds that produce H+ ions when dissolved in
water. They are composed of a hydrogen which is usually written first in the
formula and one or more nonmetals written second.
\Adding or Subtracting Significant figures - ANS - When quantities are being
added or subtracted, the number of decimal places (not significant digits) in the
answer should be the same as the least number of decimal places in any of the
numbers being added or subtracted.
\Ammonium - ANS - NH4+
\Ammonium is the only positively charged polyatomic ion. When naming
compounds with ammonium, - ANS - ammonium comes first in the name just like
it would for a positively charged ion from a metal e.g. ammonium sulfide
\An atom is the - ANS - smallest identifiable unit of an element that has properties
of that element.
\An element is - ANS - a substance that cannot be broken down into simpler
substances
\Atomic elements are those that - ANS - exist in nature with single atoms as their
basic units.
, Helium is composed of helium atoms, copper is composed of copper atoms,
mercury is composed of mercury atoms.
\Atomic Mass - ANS - is the average mass of the atoms that compose that
element, taking into account the relative abundance of the isotopes.
The unit for atomic mass is amu or atomic mass units.
\Atoms bond together to form___________ - ANS - molecules.
\Carbonate - ANS - CO32-
\Chemical changes include: - ANS - Rusting, oxidation, combustion etc
\Chemical properties- - ANS - flammability, reaction in water, radioactivity. They
are displayed through changing the chemical composition.
\Compounds - ANS - They are pure substances.
they combine in fixed, definite proportions, whereas in mixtures can have any
proportions whatsoever.
The Law of Constant Composition: All samples of a given compound have the
same proportions of their constituent elements.
E.g. 18g of water is made up of 16g of O and 2g of H.
The ratio of oxygen to hydrogen is the same for any sample and any amount of
water.
\Conservation of Matter - ANS - Matter is neither created nor destroyed.
This is the basis for balancing chemical equations.
Butane + Oxygen Carbon Dioxide + Water
58g + 208g=266g 176g+90g=266g
\Dalton's Atomic Theory - ANS - Each element is composed of tiny indestructible
particles called atoms.
All atoms of a given element have the same mass and other properties that
distinguish them from atoms of other elements.
Atoms combine in simple whole number ratios to form compounds.
\Democritus a Greek philosopher is credited with - ANS - coming up with the atom
\Endothermic reactions: - ANS - absorb energy from their surroundings as they
occur. Eg. Cold pack. When the barrier separating the reactants in a chemical
cold pack are broken the substances mix, react, and absorb heat from the
surroundings.
\Ernest Rutherford thought it would prove interesting to bombard atoms with a
positively charged beam of light. The results - ANS - of the experiments came
unexpected. Most of the alpha particles went smoothly through the foil but some
particles bounced back. They must have been repelled by something positively
charged in the center.
A chemical formula - ANS - indicates all the elements present in a compound and
the relative number of atoms of each.
Here are some chemical formulas:
H2O
NH3
O2
H2SO4
\a Danish physicist, Niels Bohr came up with and atomic theory. - ANS - RULE 1:
Electrons can orbit only at certain allowed distances from the nucleus.
RULE 2: Atoms radiate energy when an electron jumps from a higher-energy orbit
to a lower-energy orbit. Also, an atom absorbs energy when an electron gets
boosted from a low-energy orbit to a high-energy orbit.
\A formula unit is the - ANS - smallest electrically neutral collection of ions.
Formula units are different from molecules in that they do not exist as discrete
(stand alone) molecules but instead exist as part of a larger lattice. Consider table
salt for example.
\Acetate - ANS - C2H3O2-
\Acids are - ANS - molecular compounds that produce H+ ions when dissolved in
water. They are composed of a hydrogen which is usually written first in the
formula and one or more nonmetals written second.
\Adding or Subtracting Significant figures - ANS - When quantities are being
added or subtracted, the number of decimal places (not significant digits) in the
answer should be the same as the least number of decimal places in any of the
numbers being added or subtracted.
\Ammonium - ANS - NH4+
\Ammonium is the only positively charged polyatomic ion. When naming
compounds with ammonium, - ANS - ammonium comes first in the name just like
it would for a positively charged ion from a metal e.g. ammonium sulfide
\An atom is the - ANS - smallest identifiable unit of an element that has properties
of that element.
\An element is - ANS - a substance that cannot be broken down into simpler
substances
\Atomic elements are those that - ANS - exist in nature with single atoms as their
basic units.
, Helium is composed of helium atoms, copper is composed of copper atoms,
mercury is composed of mercury atoms.
\Atomic Mass - ANS - is the average mass of the atoms that compose that
element, taking into account the relative abundance of the isotopes.
The unit for atomic mass is amu or atomic mass units.
\Atoms bond together to form___________ - ANS - molecules.
\Carbonate - ANS - CO32-
\Chemical changes include: - ANS - Rusting, oxidation, combustion etc
\Chemical properties- - ANS - flammability, reaction in water, radioactivity. They
are displayed through changing the chemical composition.
\Compounds - ANS - They are pure substances.
they combine in fixed, definite proportions, whereas in mixtures can have any
proportions whatsoever.
The Law of Constant Composition: All samples of a given compound have the
same proportions of their constituent elements.
E.g. 18g of water is made up of 16g of O and 2g of H.
The ratio of oxygen to hydrogen is the same for any sample and any amount of
water.
\Conservation of Matter - ANS - Matter is neither created nor destroyed.
This is the basis for balancing chemical equations.
Butane + Oxygen Carbon Dioxide + Water
58g + 208g=266g 176g+90g=266g
\Dalton's Atomic Theory - ANS - Each element is composed of tiny indestructible
particles called atoms.
All atoms of a given element have the same mass and other properties that
distinguish them from atoms of other elements.
Atoms combine in simple whole number ratios to form compounds.
\Democritus a Greek philosopher is credited with - ANS - coming up with the atom
\Endothermic reactions: - ANS - absorb energy from their surroundings as they
occur. Eg. Cold pack. When the barrier separating the reactants in a chemical
cold pack are broken the substances mix, react, and absorb heat from the
surroundings.
\Ernest Rutherford thought it would prove interesting to bombard atoms with a
positively charged beam of light. The results - ANS - of the experiments came
unexpected. Most of the alpha particles went smoothly through the foil but some
particles bounced back. They must have been repelled by something positively
charged in the center.
