HESI A2 Chemistry Exam Questions And
Accurate Answers (A+)
Acid
a substance which is a hydrogen or proton donor. It has the property of being corrosive
to metals, turning blue litmus paper red, and having its acidity reduced when mixed with
bases
atom
the simplest unit of a molecule containing a nucleus with orbits
atomic mass
the average mass of all that elements isotopes
atomic number
number of protons in nucleus, defines an atom of an element
base
a hydrogen or proton acceptor and usually contains a hydroxide (OH) group in the
structure of the molecule. Bases are also referred to as alkaline compounds and are
chemicals that denature proteins, causing a soapy feeling; they turn red litmus paper
blue and become less basic when combined with acids.
basic unit of measure
standard unit of a system by which an amount is expressed and accounted for (grams,
liters, or meters)
,catalysts
substances that accelerate a reaction by lowering the activation energy or the amount
of energy that is needed for a reaction to occur
Clcelsius
a temperature scale used in most of the world and by scientists; It has these
characteristics:
zero degrees = freezing point of pure water at sea level
100 degrees = boiling point of pure water at sea level.
Most people have a body temperature of 37 degrees Celsius.
chemical equations
combination of elements or compounds called reactants reacting to produce a product
or end result. Equations are written in the following format: reactants ---> products. The
arrow can go the other way or both ways
combustion
a self sustaining exothermic chemical reaction ususually intitiated by HEAT acting on
OXYGEN and a fuel compound such as hydrocarbons
compound
the mixture of two or more elements or atoms
covalent bond
2 atoms share electrons, commonly in pairs, one from each atom
decomposition
a chemical reaction often described as the opposite of synthesis because it is the
breaking of a compound into its constituent parts
, deoxyribose
a sugar that is part of DNA structure
double replacement
a reaction between two ionic compounds; the positive ion from one compound combines
with the negative ion of the other compound. The resulting products are the two new
ionic compounds that have "switched partners"
electron clouds
the collection of electrons orbiting the nucleus of an atom; a cloudlike collection of
electrons
equilibrium
a state in which the reactants are being formed at the same rate as products are being
formed from the reactants.
fahrenheit
a temperature measuring system used only in US, its territories, Belize, and Jamaica. It
is seldom used for whatever scientific measurements except for the body temperature.
It has these characteristics:
0 degree is the freezing point of sea water or heavy brine at sea level;
32 degrees F is the freezing point of pure water at sea level;
212 degrees F is the boiling point pure water at sea level; most peoples' human body
temperature is 98.6 F
groups
elements that are placed together in columns in the periodic table
ionic bond
an electrostatic attraction between two oppositely charged ions or a cation and an an
ion. This type of bond is generally formed between a METAL (cation) and a NON-METAL
(anion)
isotope
the different forms of the same atom that differ in mass; for a given element, number of
PROTONS = SAME and number of
neutrons = DIFFERENT to form the distinct isotopes
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