2. • To a scientist, a reaction rate
means how quickly or slowly a
reaction takes place.
• Scientific studies have shown
that there are five factors that
affect reaction rates.
• They are temperature,
concentration, surface area,
the presence of a catalyst and
the nature of the reactants.
• Temperature is the measure of the
kinetic energy, or energy of motion,
in the particles of a substance.
• As temperature increases, the
particles move faster and come in
contact more often.
• In order for two substances to react,
the particles of those substances
must collide with each other.
• For example: Foods cook slowly at
low temperatures than at high
5. Surface Area
• For a reaction to occur, substances must
come in contact with each other.
• Contact can only take place at the surfaces
of the substances involved in the reaction.
• As the surface area increases, the rate of a
reaction increases because more particles
can come together.
• The surface area of reactants affects the
rate of reaction. If the size of a particle is
small, the surface area will be more and
this increases the speed of heterogeneous
• Concentration tells us how much solute
there is in a solution. As the
concentration of the chemical
increases, the chance of contact among
particles also increases.
• This causes an increase in the rate of
• According to collision theory, the
greater the number of molecules the
higher is the collision ratio, thus the
rate of reaction is faster.
• A catalyst is a substance that changes
the rate of a chemical reaction by
providing an alternate pathway,
lowering the activation energy.
• Most catalysts speed up reactions but
they are not changed or used up in a
• They are the same at the beginning and
end of the reaction.
• Enzymes are considered as catalysts to
speed up the biochemical reactions in
11. 1. Food and Pharmaceutical
• Temperature is a very
essential factor in preserving
foods and medicines.
• High temperatures cause
higher collision and reactions
produce by microorganisms
that are why most of food
medicinal products are
stored in low temperatures.
12. 2. Preservation or
decomposition of specimens
• Biochemical laboratories make use of liquid
nitrogen as cryogenic freezer in preserving
laboratory sample and specimens.
• This process is called cryopreservation
where cells or whole tissues are preserved
by cooling to low sub-zero temperatures.
• At low temperatures, any biological
activity, including the biochemical
reactions that would lead to cell death, is
13. 3. Medication or poison
affecting the body
• It is essential to know the right
concentration of the drugs that we
• Some drugs are more effective if taken
in higher concentrations. There are also
drugs that may poison our bodies if we
take an amount more than the
14. 4. Dating, restoration,
preservation of artifacts
• To preserve wood and leather
artifacts, these must be soaked in
• Polyethylene glycol is a waxy
substance that is absorbed into
wood and leather and makes
wood stronger and makes leather