The heat is on
Monday, 13 April 2015
C2.19 Speeding up reactionsTemperature
LO: Explain reaction rates in terms of
particles and how temperature affects this
Starter: Imagine you have a jelly baby
Your task is to dissolve this in water faster than
anyone else in the room.
How will you do this?
Write your method down in your book
Please put your bags & coats away
Objectives
• Define activation energy.
•
Describe the effect of changing
temperature on the rate of reaction.
• Explain the effect of changing
temperature on the rate of reaction.
A brief background
• Reactions take place when particles
collide with a certain amount of energy.
• The minimum amount of energy needed
for the particles to react is called the
activation energy and is different for
each reaction.
Activation
– the
minimum
amount
• In your energy
own words
write
a definition
of activation
energy
– 3have
minutes
of energy
particles
must
to react
Objectives
• Define activation energy.
•
Describe the effect of changing
temperature on the rate of reaction.
• Explain the effect of changing
temperature on the rate of reaction.
Collision theory
• The energy of collisions and the
frequency (how often) affect the rate
of reaction
• We are going to investigate how
temperature affects this.
2Mg + 2HCl
2MgCl + H2
• Investigating how temperature affects
reaction rate between magnesium ribbon
and hydrochloric acid.
Answer these questions in your book:
1. What is the dependent varible?
2. What is the independent varible?
3. Which varibles must be kept constant?
Wear your goggles
Method
Room temp. Hcl
Cold Hcl
1. Collect equipment listed on sheet
2. Measure out 10 cm3 of cold hydrochloric acid 3 cm Magnesium
ribbon
3. Take temperature and record it in the table below
4. Add a strip of magnesium and start timer
5. Stop clock when all magnesium has reacted
6. Record results in table
7. Repeat steps 2-6 for room temperature acid and warm
acid
8. Tidy away
9. Stick your sheet in your book
Hot Hcl
Method
1. Measure out 10cm3 of chilled HCl into a
boiling tube
2. Take the temperature and record it
3. Add 3cm length of Mg ribbon and start
stop watch,
4. Record how long it takes for the Mg to
be used up and record it in the table
5. Repeat using room temperature and
then warm acid
Copy and complete
Our fastest reaction was __________
Our slowest reaction was __________
Our investigation showed that as
temperature increased the rate of
reaction __________________
Objectives
• Define activation energy.
•
Describe the effect of changing
temperature on the rate of reaction.
• Explain the effect of changing
temperature on the rate of reaction.
Explaining the effect of
temperature
• So how can we explain this in terms of
particles?
Particle temperature animation
• What happens when the temperature is
increased?
WHAT WILL THIS DO TO COLLISIONS?
2 minutes in pairs to explain FULLY
SUMMING UP
• Increasing the temperature increases how
often particles collide (frequency of
collision) AND how much energy they collide
with
This means there are far more successful
collisions every second = faster rate of
reaction
Objectives
• Define activation energy.
•
Describe the effect of changing
temperature on the rate of reaction.
• Explain the effect of changing
temperature on the rate of reaction.
PROVE IT
COMPLETE THE WORKSHEET YOU
HAVE 5 MINUTES
1. What happens if particles collide with less energy than the
activation energy?
E
2.Describe what happens to the rate of reaction when the
temperature is decreased.
C
3. Use the graph to
answer these questions;
a) Explain in terms of
particle why the rate
of reaction doubles
between 60C and 80C.
b) Estimate the rate of
reaction at 30C.
A*
C2.19
1. Nothing / no reaction
2. The colder the slower/ it gets
slower / slows down
3. a) The particles move faster at
80 (deg) that they do at 60 (deg),
there are more frequent collisions
at the higher temperature, the
collisions are more energetic, and
so more likely to be successful.
b) About 36 s
Objectives
• Define activation energy.
•
Describe the effect of changing
temperature on the rate of reaction.
• Explain the effect of changing
temperature on the rate of reaction.
PROVE IT
COMPLETE THE WORKSHEET YOU
HAVE 5 MINUTES