Investigating the chemistry of how fireworks work | 14-16 years

In these two practical activities, students use party poppers and sparklers to investigate the principles behind fireworks and explore, through flame tests, what creates different colours when fireworks are set off. They work in groups to make and share their observations. The activities offer the alternative of a group experiment or demonstration for the flame test activity.

Learning objectives

Students will be able to describe:

• What is in a firework.
• What makes the different colours we see when fireworks are let off.

Sequence of activities

Introduction

Use pictures of fireworks to introduce the learning objectives. Invite students to suggest what they think might be in fireworks. Explain that they are going to do experiments to find out what is in fireworks.

Activity 1: What is a firework?

Organise students into groups of four. Give each student a copy of ’What is a firework? student sheet’.

If you prefer not to give party poppers and sparklers to every group, select students to let these off in front of the whole class, then work in groups.

Explain the task and then supervise the groups as they:

1. Let off the party poppers and burn the sparklers.
2. Complete the observation table, recording in each case what they saw and what they smelt and heard.
3. Answer questions 1‑4 on the worksheet, agreeing answers within the group.
4. Agree on a one sentence definition for a firework, for question 5.
5. Select a spokesperson to feedback their one sentence definition to the class.

Plenary 1

In a plenary, encourage students to listen to each group’s definition. Work towards a whole class definition. Ensure this includes key words such as: chemical reaction, explosive, colour agent(s), fuel, chemicals.

Activity 2: What makes the colours in fireworks?

1. Decide if you wish to carry out a demonstration or run the next activity as a practical, in groups.
2. Explain the task, to investigate what creates the colour effects in fireworks.
3. Give each student a copy of the ‘What makes the colours in fireworks? student sheet’.

Sequence for group practicals

Prepare samples, beforehand, of eight different solids in labelled Petri dishes, each with one or more flame test wires. Note that flame tests on barium and zinc salts should be demonstrated due to their toxicity.

Demonstrate barium chloride (green) and zinc chloride (white-green) to show the technique. Supervise and support as the groups:

1. Carry out flame tests on the range of solids.
2. Complete the results table provided.
3. Answer questions 1 and 2 on the sheet.
4. Select a spokesperson to give their answers to the class.

Allow about 40 minutes for the practical work. If time is short, give each group a different solid, to ensure the full range is tested, and then arrange for the results to be shared.

The alternative sequence

If using only teacher demonstrations:

1. Carry out flame tests on each substance.
2. Give time for the students to write down the colours in the table.
3. Support the groups as they answer questions 1 and 2 on the sheet.
4. Ask groups to select a spokesperson to give their answers to the class.

Allow about 25 minutes for the demonstration.

Plenary 2

Bring the students together for a plenary and:

1. Share the results from the flame tests, if a class experiment was done.
2. Give each student a copy of the periodic table, or ensure one is available.
3. Lead the discussion as the groups give their answers to the two questions:
   • For question 1: The metallic elements in the compounds create different colours. Their ions have different structures. The structural differences between the ions cause the different colours.
   • For question 2: Heat is needed to see the colours. Heat is used to excite electrons in the metallic elements. The excited electrons give out light energy of different wavelengths (colours) as they move within the ions.
4. Draw out key points in the discussion.
5. Use the periodic table to link the results to atomic structures and positions of elements in the table.
6. Pose further questions to take the key points further, depending on the level of the students:
   • What do they notice about where the elements used in fireworks are located?
   • Why are not all metallic elements used in fireworks?

Feedback

Collect students’ worksheets from both experiments and give written feedback reinforcing the good qualities of the points raised by the students.

Commentary

The fireworks context provides a vehicle for students to share thinking and to help them make the connection between properties and the periodic table, as well as to learn about a familiar item.

The collaboration needed in group discussions and experimental work – as they listen and give feedback – necessarily involves students in evaluating each other’s work.

Questions and feedback, during the plenary, lead the students to make the appropriate connections between experimental results and chemical theory. Written feedback supports students as they develop their thinking in this area.

Practical notes

Equipment

For each student:

• Eye protection
• A copy of, or access to, the periodic table

NOTE: See the teacher sheets for each experiment to full details of the apparatus and chemicals required.

Health, safety and technical notes

1. Read our standard health and safety guidance.
2. Wear eye protection.
3. It is the responsibility of the teacher to carry out appropriate risk assessments.

NOTE: See the teacher sheets for each experiment for full ’Health, safety and technical notes’, including preparation notes.

Answers

What is a firework?

1. The explosive lifts the streamers out of the container. The explosive is ignited when the cord is pulled.
2. The solid substance reacted with oxygen in the air. Gases were made which went into the air. Iron was in the sparkler. The iron filings were heated up and also went into the air.
3. The heat from the chemical reaction produced the sparks. The iron filings heated up and gave off light.
4. Colour, light, lifting charge, heat and smoke.
5. A firework is …an explosive mixture comprising a mixture of substances where the mixture includes fuel, a supply of oxygen and other chemicals to create effects.

What makes the colours in fireworks?

1. The metallic elements have different numbers of electrons. These are affected by the heat energy in different ways, giving out light of different colours.
2. Heat is used to excite the electrons.