Rate of Chemical
Reactions
Unit 1
MYP 4
Unit: Particles on the move
Key Concept: Systems
Related Concept: Consequences and Conditions
Global Context: Scientific and Technical Innovation (methods, products, processes and
solutions)
Statement of Inquiry: Improving existing systems & minimising consequences requires
the manipulation of conditions of existing processes or development of new methods
ATL: Thinking: Critical Thinking
Learner Profile: Thinkers
Content Agenda
Signs of Chemical reaction
Defining reaction rate
The Collision theory
Factors affecting reaction rate
What are the signs of chemical reaction?
●
Change of color.
●
Change of odor.
●
Change of Temperature.
●
Evolution of a gas (formation of bubbles)
●
Change in state of matter
●
Input or release of energy/heat
●
Explosion
●
Sound
●
Precipitate (formation of a solid) not in this ex
How to define the Reaction Rate?
The speed at which a chemical reaction proceeds.
It is often expressed in terms of either:
● the concentration of a product that is formed in a unit of time
Or
● the concentration of a reactant that is consumed in a unit of time.
Engage:
Lab Investigation
Sodium Thiosulfate + Hydrochloric acid
Na2S2O3 (aq) + 2HCl (aq)
Sodium Chloride + Water + Sulphur + Sulfur Dioxide
2NaCl (aq) + H2O(l) + S(s) + SO2(g)
Factors affecting the rate of reaction:
● Concentration
● Temperature
● Surface area
● Presence or absence of Catalyst / Inhibitor
● Reactivity of metals
Phet Collorado
In order for a reaction to take place, what
do you think should happen?
Study: Collision Theory
States that reacting particles must collide in the correct orientation and with
enough kinetic energy that they form products
If reactant particles do not collide with enough energy and with right orientation, they
will not react together. In reality, only a small fraction of the overall collisions, are
effective collisions, that result in a chemical reaction.
Activation
energy
https://www.youtube.com/watch?v=wbGgIfHsx-I
Watch this video to find out what is activation energy?
What must happen for a reaction to happen?
What affects
reaction rate?
Concentration
With an increase in the
concentration of any reacting
substance, the chances for
collisions between molecules are
increased because there are more
molecules per unit of volume.
Temperature
As temperature increases, molecules gain
energy and move faster and faster.
Therefore, the greater the temperature, the
higher the probability that molecules will
be moving with the necessary activation
energy for a reaction to occur upon
collision.
Surface Area
If the surface area of a reactant is
increased: more particles are
exposed to the other reactant. there
is a greater chance of particles
colliding, which leads to more
successful collisions per second. the
rate of reaction increases.
Catalysts and inhibitors
A catalyst is a substance that speeds up the
rate of the reaction without being consumed
by the reaction itself. It works by lowering
the activation energy by providing an
alternative pathway that requires less energy
to produce the activated complex. Like
enzymes, a biological catalyst.
Inhibitors
A catalyst inhibitor is a substance
that decreases the rate of, or
prevents, a chemical reaction, i.e.
it opposes the effect of a catalyst.
Activate
HW
On Managebac Worksheet