In this activity, models are used to describe chemicals
and chemical reactions. Students work in groups to investigate iron and
This provides an opportunity for students to:
- reinforce and build upon ideas of elements, mixtures and compounds
- investigate the reaction between two elements to make a compound
- describe a chemical change using the particle model.
The session combines well-established practical work with the use of
the particle model to explain what is happening. Students begin by looking
at the properties of iron, sulfur and a mixture of the two. They draw
particle diagrams to represent the elements. Three-dimensional models
might be shown as well.
The reaction between iron and sulfur is demonstrated and the product is
examined. Students are told the product iron sulfide consists of equal
numbers of iron and sulfur atoms chemically joined (combined). They are
asked to model the change in a role play.
Students will be able to:
- distinguish between elements, compounds and
- relate formulae to the numbers and types of atom in a compounds
Sequence of activities
||Display samples of iron, sulfur and a mixture of iron
and sulfur. Describe iron and sulfur as elements, and the other sample
as a mixture.
Give each student a copy of the Elements,
compounds or mixtures? sheet.
Ask students to:
- work in pairs
- explain what they think the words element, compound and mixture
Share the learning objectives with students.
||Tell the students that, working in pairs, they
are going to examine the samples of iron, sulfur and the mixture using
a magnifying glass, a magnet, warming and dilute sulfuric acid.
(If available, show the difference in brittleness of iron and sulfur.)
Hand out copies of the Comparing iron, sulfur and a mixture of the
Ask pairs of students to:
- record their observations using the table
- sketch diagrams of the arrangement of particles
in the three samples, on a mini whiteboard.
Invite or choose pairs to show and explain their drawings. Ask
other students to comment. Spend time discussing the merits of the
drawings and allow pairs time to modify their sketches on the
Finally, ask students to copy their final drawings onto the table
||Lead a class discussion on the nature of the
particles, aiming to draw out the ideas:
- all stuff is made of atoms
- pure substances made from just one type of atom are called
- each element is represented by a symbol, eg Fe for iron and
S for sulfur.
||Either demonstrate the effect of strongly heating
iron and sulfur together or supervise pairs of students as they carry
out the demonstration in A compound from two elements.
students to examine the product and compare its properties with those
of the elements and the mixture.
||Rearrange students into groups of 3‑4. Ask them to:
- devise a role play activity that would involve the whole class
acting out the reaction between iron and sulfur
- describe what they would do.
Invite the class to vote on the one they think is the best – and
then act it out.
||Draw the session(s) to an end by leading a class
discussion about the nature of the particles. Reinforce that:
- pure substances made up of different kinds of atoms
chemically joined together are called compounds
- particles in a compound are identical, each made up of the
same set of atoms
- the formulae of a compound shows the type and numbers of
atoms in its particles, eg FeS.
Write up a word equation and a symbol equation to conclude the
||Ask students to look at what they wrote on
Elements, compounds or mixtures? and to make any changes in light
of the session. Take in the sheets and give written feedback that will
support the individual student.
Assessment for learning commentary
An interesting opening to the session, with a brief self diagnosis,
will encourage attentiveness at the outset.
Collaboration between students, comments about particle arrangement and
the simple vote on the role-play means that they are evaluating each
other’s work throughout the session.
The importance of this topic demands that the student sheets are
scrutinised carefully. Written guidance to help each individual is
- Samples of iron, sulfur (Flammable) and a mixture
of iron and sulfur.
||Elements, compounds or mixtures? for each
||Linking phrases sheet 1 for each student
||A compound from two elements.
||Mini whiteboard for each pair of students
It is the responsibility of the teacher to carry out an appropriate
- Bunsen flame
- Sulfur (Flammable)
- Iron powder (potential Irritant)
- Dilute sulfuric acid (Irritant)
K. Hutchings, Classic chemistry experiments. London: Royal
Society of Chemistry, 2000.