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ScienceYear 9 Science: inheritance, energetics, climate, magnetism and space30 min★★★ difficulty

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
  • 19 parts to scroll through
  • 4 quick checks
  • Marked quiz at the end
  • Gentle pace: short sittings with pauses

Words to know

exothermicendothermicchemicalreactionsreactivity

Scroll down — the lesson carries on below

Part 1 of 19 · Discover5%
1

Watch & discover

Part 1 of 19

Watch first

Exothermic, endothermic and the reactivity series

An English teaching video on this topic from LearnScienceWithB. Watch it, then scroll down for the lesson.

In a nutshell

Understand exothermic and endothermic chemical reactions and the reactivity series of metals

2

What you already know

Part 2 of 19

Before we start

What you already know

You should already be able to write a word equation and know that metals react with acids.

Recap: science-y8-acids
3

Key words

Part 3 of 19

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.
4

Learning cycle

Part 4 of 19

Learning cycle 1 of 2

Energy in and energy out

A short piece of teaching, then a check to make sure it has landed.

5

Explore the idea

Part 5 of 19

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.

6

Explore the idea

Part 6 of 19

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.

7

Quick check

Part 7 of 19

Quick check

A reaction that raises the temperature of its surroundings is...

8

Quick check

Part 8 of 19

Quick check

Thermal decomposition is usually...

9

Reset break

Part 9 of 19

Pause

That's sitting 1 of 2 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.

Stop here for now
10

Learning cycle

Part 10 of 19

Learning cycle 2 of 2

Ordering metals by reactivity

A short piece of teaching, then a check to make sure it has landed.

11

Explore the idea

Part 11 of 19

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.

12

Explore the idea

Part 12 of 19

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.

13

Quick check

Part 13 of 19

Quick check

Which metal is most reactive?

14

Quick check

Part 14 of 19

Quick check

Zinc is added to copper sulfate. What happens?

15

Common mix-ups

Part 15 of 19

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.
16

Challenge round

Part 16 of 19

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

17

Challenge round

Part 17 of 19

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.

18

Mastery quiz

Part 18 of 19

Marked quiz

End of lesson quiz: Exothermic, endothermic and the reactivity series

6 questions, marked with the reasoning shown. No timer.

  1. 1. Bond breaking is...

  2. 2. Combustion is an example of...

  3. 3. Which metal does not react with dilute acid?

  4. 4. Iron is added to copper sulfate solution. The blue colour...

  5. 5. Aluminium is extracted by electrolysis because it is...

  6. 6. In an endothermic reaction the thermometer reading...

19

Lesson round-up

Part 19 of 19

Lesson round-up

Ready when you are

Quiz score

Not sat

Games

Not played

Points this lesson

0

Best run

0 in a row

Luna: 0 out of 4 on the practice checks. Only if you feel up to it — one more?

Ask Luna

Do the work

Your written work for this lesson

This is the part you'd do in your book at school. Pick the pieces below, write here or on paper, and photograph anything you draw or work out.

Case study

Why the school greenhouse failed

A science club grew tomato plants in the school greenhouse. In June the plants grew well: leaves were dark green and the fruit set quickly. In July the club went away for two weeks and left the greenhouse door shut. When they came back, the leaves were curled and pale and most of the fruit had dropped.

The club had a data logger inside. It showed the temperature reached 46 °C on several afternoons and the soil moisture fell close to zero. The club knew photosynthesis needs light, water and carbon dioxide, and that enzymes in a plant work best in a narrow range of temperature. Above that range the enzymes stop working properly.

The club repeated the summer with the door propped open and a water bottle drip on each pot. Temperature peaked at 31 °C and the plants survived.

Written for Good Learning Co.

Reading questions

  1. Name the variable the club changed the second time, and one variable they kept the same.
  2. Explain, using the words photosynthesis and enzymes, why the plants were damaged in July.
  3. Write a conclusion for the club's report, saying how far the evidence supports it.

  • Method and results

    Writing

    Write the aim, what you changed, what you measured and what you kept the same, then record your results in a table.

    1 page + results table

  • Conclusion

    Writing

    Explain what your results show and why, using the scientific words from the lesson. Say how you know you can trust them.

    6–8 sentences

  • Labelled diagram

    Diagram

    Draw the apparatus or the process in pencil, label it fully, and photograph it.

    1 labelled diagram

  • Reading and notes

    Reading

    Read the lesson text again and write the key ideas in your own words.

    Half a page of notes

Saved as you type.

Part 1 of 19 · Watch & discover

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