Transcript CHEMICAL INTERACTIONS

CHEMICAL
INTERACTIONS
Chapter 1 - Chemical Reactions
Outline/Review
1.1 Matter and Its Changes
• CHEMISTRY is the study of the properties
of matter and how matter changes.
• An ELEMENT is a substance that cannot be
broken down into any other substances by
chemical or physical means.
• All the matter around you is composed of
one element or a combination of two or
more elements.
•A COMPOUND is a substance made of two
or more elements chemically combined in a
specific ratio.
•An example of a compound is CO2
•A MIXTURE is made from two or more
elements or compounds in the same place but
not forming new material.
•A SOLUTION is a well-mixed mixture where
substances are not easily seen.
•Chemistry is the study of the kinds of and
changes in matter.
•A PHYSICAL CHANGE is when the form or
appearance of a material changes.
•An example of a physical change is water in
the forms of ice, water, and water vapor.
•A CHEMICAL CHANGE is when a new
substance is produced.
•An example of a chemical change is metal
rusting.
•The change of font type is an example of a
physical change.
•Changing what something says is an example of
a chemical change.
•You can observe a chemical reaction by
observing changes in the properties of matter.
•A PRECIPITATE is a solid formed during a
chemical reaction.
Some of the evidence for chemical reactions is:
•production of a gas
•precipitation of a solid
•a change in temperature (either up or down)
•a color change
•change in physical properties
•The smallest particle of an element is an
ATOM.
•A MOLECULE is the combination of two or
more atoms.
•An example of a molecule is H2O
•An example of an atom is H
•A CHEMICAL BOND is the force that holds
atoms and molecules together.
•Chemical reactions occur when chemical bonds
are either formed or broken apart.
Therefore, to summarize . . .
• Matter may be in the form of elements,
compounds, or mixtures.
• Chemical changes result in the formation of
new substances.
• Color change, production of a gas or a
precipitate, a change in temperature, or a
change in the properties of a substance are
all clues that a chemical reaction has taken
place.
• Chemical reactions occur when chemical
bonds are formed or broken
1.2 Describing Chemical Reactions
• A CHEMICAL EQUATION is a shorter,
easier way to show chemical reactions.
• Most elements are represented by a 1-2
letter symbol.
• An example of a symbol is O for oxygen.
• A compound is represented by a “word”,
called a CHEMICAL FORMULA.
• An example of a chemical formula is H2O.
• A SUBSCRIPT shows the number of atoms
of an element in a molecule.
•The materials you have at the beginning of a
reaction are the REACTANTS.
•The materials you have at the end of a reaction
are called the PRODUCTS.
•A chemical equation uses symbols to show the
reactants and products of a chemical reaction.
•An example of a chemical reaction is:
H2 + O2 -----> H2O2
(H2 and O2 are the reactants while H2O2 is the
product.)
•All the atoms present at the start of a reaction
are present at the end.
•The law of conservation of mass states:
The amount of matter in a chemical reaction does
not change, so the total mass of the reactants
must equal the total mass of the products.
•A balanced chemical equation has the same
amount of atoms for the reactants and the
products.
•A COEFFEICIENT can be added to balance the
number of atoms in an equation.
An example of a balanced equation is:
2 Mg + O2 -----> 2 MgO
•Many reactions can be classified in one of
three categories:
•SYNTHESIS
•DECOMPOSITION
•REPLACEMENT
•A SYNTHESIS reaction occurs when two or
more substances combine to make a more
complex compound.
•An example of a synthesis reaction is:
2 SO2 + O2 + 2 H2O -----> 2 H2SO4
•A DECOMPOSITION reaction breaks down
compounds into simpler products.
•An example of a decomposition reaction is:
2 H2O2 -----> 2 H2O + O2
•A REPLACEMENT reaction is when one
element replaces another in a compound OR
when two elements trade places.
•Examples of two replacement reactions are:
2 CuO + C -----> 2 Cu + CO2
MgCl2 + K2S -----> MgS + 2 KCl
Therefore, to summarize . . .
• A chemical equation uses symbols to show
the reactants and products of a chemical
reaction.
• Matter is neither created nor destroyed
during a chemical reaction.
• Chemical reactions may be classified by the
types of changes in reactants and products.
1.3 Controlling Chemical Reactions
• Every chemical reaction involves a change
of energy. Some reactions release energy
and others absorb energy.
• An EXOTHERMIC reaction releases
energy in the form of heat.
• An ENDOTHERMIC reaction absorbs
energy and feels cold.
• ACTIVATION ENERGY is the amount of
energy needed to get a reaction started.
•The rate of a reaction is affected by such factors
as concentration, surface area, and temperature.
•Increasing the CONCENTRATION is one way
to increase the rate of a reaction.
•Increasing the SURFACE AREA is another way
of speeding up a reaction.
•Increasing the TEMPERATURE is a third way
to speed up a reaction.
•A CATALYST is a material that lowers the
activation energy needed to start the reaction.
•A type of biological catalyst is an ENZYME.
•Enzymes provide a surface for the reactions to
take place.
•An INHIBITOR is a material used to slow down
a reaction - often to make it less dangerous.
Therefore, to summarize . . .
• Every chemical reaction involves a change
in energy. Some reactions absorb energy
and others release it.
• The rate of a chemical reaction can be
controlled by such factors as concentration,
surface area, temperature, and use of a
catalyst or inhibitor.
1.4 Fire and Fire Safety
• The rapid reaction between oxygen and a
fuel is called COMBUSTION.
• A FUEL is a material that releases energy
when it burns.
• Three things are necessary to start and
maintain a fire--fuel, oxygen, and heat.
• Water removes two parts of the fire triangle-heat and oxygen.
•Some of the most common sources of fires are
small heaters, kitchen fires, faulty electrical
wiring, and carelessness with cigarettes (the
most deadly).
•Use baking soda to put out a fire that starts on
the stove.
•Try to extinguish small fires yourself, but leave
a growing fire to the fire department.
•Prevention is the best form of fire safety.
Therefore, to summarize . . .
• The fire triangle shows the three things
necessary to start a fire and keep it burning:
fuel, oxygen, and heat.
• Water stops combustion by keeping the fuel
from coming in contact with oxygen. Also,
evaporation of water uses a great deal of
heat and cools the fire.
This concludes the Chapter 1
review for the Chemical
Interactions book.
STUDY WELL!