C2.19 Speeding up reactions- Temperature

LO: Explain reaction rates in terms of particles and how temperature affects

this

The heat is on Thursday 20 April 2023

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 bookPlease 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.

• In your own words write a definition of activation energy – 3 minutesActivation energy – the minimum

amount of energy particles must have 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

1. Collect equipment listed on sheet2. Measure out 10 cm3 of cold hydrochloric acid3. Take temperature and record it in the table below4. Add a strip of magnesium and start timer5. Stop clock when all magnesium has reacted6. Record results in table7. Repeat steps 2-6 for room temperature acid and

warm acid8. Tidy away9. Stick your sheet in your book 

Goggles & tidy work space

Cold HclHot Hcl

Room temp. Hcl

3 cm Magnesium ribbon

Method1. Measure out 10cm3 of chilled HCl into

a boiling tube2. Take the temperature and record it3. 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 table5. 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 ITCOMPLETE THE WORKSHEET YOU HAVE 5

MINUTES

1. What happens if particles collide with less energy than

the activation energy?

2.Describe what happens to the rate of reaction when the

temperature is decreased.

E

C3. 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 reaction2. 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 ITCOMPLETE THE WORKSHEET YOU HAVE 5

MINUTES