Atoms: size, scale and nanoscience | 14-16 years

In this activity, students are invited to imagine the unimaginable – how small an atom is – and are introduced to the concept of nanoscience. They begin with a thought experiment about size, leading to the idea that atoms are extraordinarily small, but they do exist.

Learning objectives

Students will be able to explain that:

• Atoms exist, but are very small, and there are different types.
• A substance made of only one type of atom is called an element.
• An atom is the smallest part of an element that remains recognisable as the element.

Sequence of activities

Introduction

Display samples of elements in bottles labelled with both their name and mass. Tell the students that each sample contains the same number of atoms. Ask them to start thinking about the idea of atoms and how small they are.

Definitions of atoms and elements

Arrange students in pairs. Give each student a copy of ‘Definitions of atoms and elements’. Ask them to:

1. Answer the two questions.
2. Swap answer sheets.
3. Explain to their partner whether they agree or disagree (giving reasons) with what each has written.

Stimulus

Reveal the learning objective. Explain they will be trying to get a feel for how small atoms are. As a stimulus to begin this investigation of size, show students some suitable images and describe the different magnifications.

It’s a small world: stage 1

Hand out copies of ’It’s a small world’. Ask students to work in their pairs to:

1. Answer the questions on the sheet.
2. Write on a mini whiteboard an answer to question 1.
3. Reveal their answers simultaneously.

Tell students the actual number ‑ an opportunity to introduce or reinforce the concept of powers of 10. Emphasise that the number is almost too small to visualise (even a large sports stadium only holds around 100 000 or 105).

It’s a small world: stage 2

Arrange for the pairs to split up and join a new group of three or four students. Ask the new groups to:

1. Look at each other’s answers to question 2 and see if they agree.
2. Write the name of the smallest item on their lists on a whiteboard.

Plenary 1

In a mid‑session plenary:

1. Choose a volunteer from each group to hold up the name of the item.
2. Invite the class to put the items in order by getting the volunteers to stand in the correct order.
3. Ensure each student makes a note of the final list.

Atoms and elements: stage 1

Move the students back to their original pairs. Hand out bags of dried beans, lentils, rice, sugar and salt. Ask the pairs to:

1. Estimate how many individual things there are in 1 kg of each.
2. Write their estimate on a group grid (a large piece of paper on notice board, or a grid drawn on a whiteboard).

Plenary 2

In a mid-session plenary

1. Select students to describe what pattern they notice in the class results.
2. Invite others to comment or ask questions.

Atoms and elements: stage 2

Give each pair an iron filing in a small stoppered sample tube. Ask them to:

1. Estimate how many iron atoms are in the filing.
2. Think about the bags of beans etc, and how this might help them picture the atoms of different elements.
3. Write down the names of elements they saw at the beginning, in order of increasing mass.
4. Write an explanation.

Plenary 3

In a plenary, invite students to describe the sizes of atoms found in different elements.

Commentary

As well as the questions on the worksheets, students are prompted by questions throughout the activities and are invited to raise their own questions. By the nature of the discussions there is some informal peer assessment. Teacher assessment and feedback is light-touch, so that students are encouraged to visualise the comparisons for themselves.

Equipment

For each pair of students:

• Mini whiteboard
• Bags of dried beans, lentils, rice, sugar and salt, with the mass shown on the bag
• A single iron filing in a sample tub

For the stimulus, you can either use images showing different magnifications of an object (eg human hair) or refer to a resource such as Secret worlds: the universe within from Molecular Expressions by The Florida State University.

Answers

1. About 1.35 x 10⁶ hydrogen atoms would be alongside each other in 1 cm.