24 Iron and sulfur 11-14 Working in groupsSelf assessmentPeer assessmentSharing objectives and criteriaQuestioningUsing feedbackUsing tests

In this activity, models are used to describe chemicals and chemical reactions. Students work in groups to investigate iron and sulfur.

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.

Learning objectives

Students will be able to:

  1. distinguish between elements, compounds  and mixtures
  2. 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 mean.

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 two sheet.

Ask pairs of students to:

  1. record their observations using the table provided
  2. 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 white-boards.

Finally, ask students to copy their final drawings onto the table provided.

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 elements
  • 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.

Ask 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 discussion.

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 essential.

Resources

Stimuli

  • Samples of iron, sulfur (Flammable) and a mixture of iron and sulfur.

Props

Download Word Download PDF Elements, compounds or mixtures? for each student
Download Word Download PDF Linking phrases sheet 1 for each student
Download Word Download PDF A compound from two elements.
    Mini whiteboard for each pair of students

Safety notes

It is the responsibility of the teacher to carry out an appropriate risk assessment.

Principal hazards

  • Bunsen flame
  • Sulfur (Flammable)
  • Iron powder (potential Irritant)
  • Dilute sulfuric acid (Irritant)
  • Powders

Acknowledgement

K. Hutchings, Classic chemistry experiments. London: Royal Society of Chemistry, 2000.