Exothermic, endothermic and the reactivity series
Some reactions warm your hands and others chill them. Behind both is the same idea: energy is needed to break bonds and released when new ones form.
Lesson overview
What you'll learn in this lesson
Understand exothermic and endothermic chemical reactions and the reactivity series of metals
Key learning points
- • Exothermic reactions
- • Endothermic reactions
- • Ordering metals
- • Displacement and extraction
This lesson at a glance
- 30 minutes
- 25 parts to scroll through
- 4 quick checks
- Marked quiz at the end
- Gentle pace: short sittings with pauses
Words to know
Scroll down — the lesson carries on below
Watch & discover
Part 1 of 25
Visual introductionPicture this
Exothermic, endothermic and the reactivity series
Some reactions warm your hands and others chill them. Behind both is the same idea: energy is needed to break bonds and released when new ones form.
In a nutshell
Understand exothermic and endothermic chemical reactions and the reactivity series of metals
What you already know
Part 2 of 25
Before we start
What you already know
You should already be able to write a word equation and know that metals react with acids.
Key words
Part 3 of 25
Key words
Words you'll need today
- Exothermic
- A reaction that transfers energy out, warming the surroundings.
- Endothermic
- A reaction that takes energy in, cooling the surroundings.
- Reactivity series
- Metals listed in order of how readily they react.
- Displacement
- A more reactive metal taking the place of a less reactive one.
Reset break
Part 4 of 25
Pause
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Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Learning cycle
Part 5 of 25
Learning cycle 1 of 2
Energy in and energy out
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 6 of 25
Learn
Exothermic reactions
In an exothermic reaction the energy released as new bonds form is greater than the energy needed to break the old ones, so the surplus warms the surroundings and the temperature rises. Combustion, neutralisation and most oxidation reactions are exothermic. Hand warmers use a controlled exothermic reaction; a temperature rise measured in a polystyrene cup is the classroom evidence.
Explore the idea
Part 7 of 25
Learn
Endothermic reactions
In an endothermic reaction more energy is taken in to break bonds than is released when new ones form, so energy is drawn from the surroundings and the temperature falls. Thermal decomposition and the reaction between citric acid and sodium hydrogencarbonate are examples. Sports cold packs use this deliberately. Energy is not created or destroyed in either case; it is transferred.
Reset break
Part 8 of 25
Pause
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Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Quick check
Part 9 of 25
Quick check
Part 10 of 25
Learning cycle
Part 11 of 25
Learning cycle 2 of 2
Ordering metals by reactivity
A short piece of teaching, then a check to make sure it has landed.
Reset break
Part 12 of 25
Pause
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Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Explore the idea
Part 13 of 25
Learn
Ordering metals
The reactivity series lists metals from most to least reactive: potassium, sodium, calcium, magnesium, aluminium, zinc, iron, copper, silver, gold. Reactions with water and with dilute acid provide the evidence. Potassium fizzes violently with cold water, magnesium reacts steadily with acid, and copper does not react with dilute acid at all. Position predicts behaviour.
Explore the idea
Part 14 of 25
Learn
Displacement and extraction
A more reactive metal displaces a less reactive one from its compound: iron added to copper sulfate solution gives iron sulfate and copper, and the blue colour fades. The same order explains extraction. Metals below carbon can be extracted by reduction with carbon, while very reactive metals such as aluminium need electrolysis, which is why aluminium became widely usable only relatively recently.
Quick check
Part 15 of 25
Reset break
Part 16 of 25
Pause
That's sitting 4 of 6 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Quick check
Part 17 of 25
Common mix-ups
Part 18 of 25
Common mix-ups
Things people often get wrong
- People often think endothermic means cold. It means energy is taken in, which is why the surroundings cool.
- People often think displacement works either way. Only the more reactive metal displaces the less reactive one.
Challenge round
Part 19 of 25
Game · Sort it
Which of these are true?
Drag each card into the right column. Tap a card first if dragging is fiddly.
True
Not true
Reset break
Part 20 of 25
Pause
That's sitting 5 of 6 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Challenge round
Part 21 of 25
Game · Fill the gaps
Finish the sentences
Choose the word that belongs in each gap.
In an ____ reaction the energy released as new bonds form is greater than the energy needed to break the old ones, so the surplus warms the surroundings and the temperature rises.
Combustion, neutralisation and most oxidation ____ are exothermic.
In an ____ reaction more energy is taken in to break bonds than is released when new ones form, so energy is drawn from the surroundings and the temperature falls.
Challenge round
Part 22 of 25
Game · Recall cards
A reaction that raises the temperature of its surroundings is...
Card 1 of 4
Exit quiz
Part 23 of 25
Exit quiz
Show what you've learned
6 questions, marked together at the end. Nothing is timed.
1. Bond breaking is...
2. Combustion is an example of...
3. Which metal does not react with dilute acid?
4. Iron is added to copper sulfate solution. The blue colour...
5. Aluminium is extracted by electrolysis because it is...
6. In an endothermic reaction the thermometer reading...
Mastery quiz
Part 24 of 25
Marked quiz
End of lesson quiz: Exothermic, endothermic and the reactivity series
4 questions, marked with the reasoning shown. No timer.
1. A reaction that raises the temperature of its surroundings is...
2. Thermal decomposition is usually...
3. Which metal is most reactive?
4. Zinc is added to copper sulfate. What happens?
Lesson round-up
Part 25 of 25
Lesson round-up
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