Magnetic Marbles

Demonstration Kit

Introduction

Collision theory, like many chemistry topics, is abstract. Teaching, as well as learning abstract topics, is difficult. An activity or model makes an abstract topic seem less abstract and learning (as well as teaching) much easier. This magnetic marbles activity is a fun way of learning about the collision theory

Concepts

  • Collision theory
  • Chemical reactions
  • Energy

Materials

Marbles, 32 (one per student)*
Pencils (one per student)
String, 60 cm (one for every six students)
*Materials included in kit.

Safety Precautions

This activity is considered to be relatively nonhazardous. Follow all standard laboratory safety guidelines.

Prelab Preparation

  1. The day before the activity, tell students that the following day they will be sitting on the floor and therefore should wear appropriate (old) clothes.
  2. Before class, push all desks aside and sweep the floor if it needs to be swept. This demonstration requires a hard, flat survace, such as a tile floor. 

Procedure

  1. As students walk in the door, hand each of them one marble and tell them to sit on the floor with five of their classmates. The students should be sitting in groups of six.
  2. When all students are sitting in groups, hand each group a 60-cm string. Instruct them to draw a circle with a 60-cm radius on the floor using a pencil. They should use the string to measure the radius. The string can be used like a drawing compass—one end is held down and a pencil is tied to the other end.
  3. Explain to students that their circle represents a reaction vessel and each marble represents an atom. Their goal is to create as many molecules as they can by rolling their atom towards another atom. They should keep their hands and body outside the circle at all times. A molecule is formed when two atoms (marbles) stick together or react.
  4. If a student’s marble does not react, it can be picked up by another student and used again. Each group should keep track of the number of pairs they make and when a pair is made, the marbles should be pulled apart and used again.
  5. Student will learn that the aim, initial speed and angle of collision are important factors affecting the success of the reacting pairs.

Teacher Tips

  • Don’t worry about the pencil marks on the floor—they will be light and will wear off by the next day.
  • As an extra incentive, tell students their grade is based on the number of pairs they form or maybe give the best group extra credit points.
  • Upon completion of this activity discuss as a class the following questions. How would decreasing the volume of the reaction vessel affect the reaction rate? How would increasing the concentration of atoms affect the reaction rate? What could be done to simulate a catalyst? (Optional) Allow students time to test their hypothesis to these questions before discussion.

Correlation to Next Generation Science Standards (NGSS)†

Science & Engineering Practices

Constructing explanations and designing solutions

Disciplinary Core Ideas

MS-PS2.A: Forces and Motion
HS-PS2.A: Forces and Motion

Crosscutting Concepts

Systems and system models

Performance Expectations

MS-PS2-1. Apply Newton’s Third Law to design a solution to a problem involving the motion of two colliding objects.

Discussion

A successful collision between reactants in a reaction system is a collision where molecules not only collide, but also form an activated complex that then goes on to form products. Concentration, pressure and the number of particles colliding affect the number of collisions that occur per unit time. These factors, plus the collision geometry, then determine if a collision will be successful. The frequency at which successful collisions occur determines the rate of the chemical reaction.

Increasing the concentration or pressure of reactant molecules increases the number of molecules in a given area. As molecules move, they are more likely to collide with other molecules simply because the molecules are more densely packed. The same fraction of collisions will produce products, but because more collisions are occuring overall, a higher number of successful collisions will occur.

For three particles to collide, three reactants must be in exactly the same place at the same time. The probability of this occurring is less than for just two particles to be in exactly the same place at the same time. Therefore, if an overall reaction contains three reactants, the reactants most likely combine in steps—a reaction mechanism—that consist of smaller reactions between only two particles.

In a reaction system, the spatial orientation of reactants must be such that it allows the formation of new bonds in the activated complex to begin. Many collisions may occur, but only those that collide with the correct orientation will produce a successful collision.

References

Special thanks to Ms. Anne Mundy, chemistry teacher, Half Hollow Hills High School West, Dix Hills, NY, who provided us with the ideas for this activity.

†Next Generation Science Standards and NGSS are registered trademarks of Achieve. Neither Achieve nor the lead states and partners that developed the Next Generation Science Standards were involved in the production of this product, and do not endorse it.