l

Usually, when matter and antimatter meet they are destroyed!

matter antimatterBANG!

l

Protons are positive and electrons are

negative. When they meet, they destroy

each other!

+-BANG!

+-BANG!

+-BANG!

-

+

-

-

-

+

+

+

+

+BANG!

BANG!BANG!

BANG!

What will be left when the dividing wall is removed?

I want there to be three positives left when I remove

the wall. I can add more positives, take some positives out, add some negatives in or

take some negatives out

-

+ +

++

-

-

What will be left when the dividing wall is removed?

What should I do?

Inside this box is my own, miniature Large Hadron Collider. It has some positives and

some negatives in it. The overall total is negative two.

+

+++

++

-2

I put in six positives.What does this make the

total charge in my mini Large Hadron Collider?

How could you write this down?

---5

This time I have a charge of -5 and I take out a couple of

negatives.What’s the total charge in my mini

Large Hadron Collider?How could you write this down?

It’s in the News!Antimatter

Teacher Notes

Antimatter

Introduction: The Large Hadron Collider, at Cern, is rarely out of the news! Recently, in a story that could be taken from Star Trek, it was announced that scientists there

hadtrapped antimatter!

When matter and antimatter meet they destroy each other and, in this It’s in the News!, this context is used to offer an image for students to develop theirunderstanding of addition and subtraction with negative numbers.

This week’s activity is more focussed and less open-ended than many It’s in the News! resources but is intended as the catalyst for student discussion, not just

for answering the questions posed in the slides.

Content objectives:This context provides the opportunity for teachers and students to explore a number of objectives. Some that may be addressed are:• understand negative numbers as positions on a number line; order, add and subtract integers in context• use logical argument to interpret the mathematics in a given context or to establish the truth of a statement.

Process objectives: These will depend on the amount of freedom you allow your class with the activity. It might be worth considering how you’re going to deliver the activity andhighlighting the processes that this will allow on the diagram below:

Activity:This activity uses matter and antimatter as a context to help students develop an image of the additive relationship with positive and negative numbers. Students are introduced to the idea of matter and antimatter and that, when they meet, they destroy each other. Students are then offered some situations towork with, involving unequal amounts of matter and antimatter. In themselves, these situations are unlikely to be enough to develop a full understanding ofaddition and subtraction of negative numbers, and this is not the intention of the PowerPoint. However, these slides, with discussion and input from the

teacher,can facilitate another image of these operations which may allow students to move on from the ‘two negatives make a positive’ rules without reason.

Differentiation:To make the task easier you could consider:• providing the students with counters • asking the students to draw each situation on mini-whiteboards. This allows them to wipe out one positive/negative pair at a time.

To make the task more complex you could consider:• asking for a short piece of writing explaining what happens when positive and negative numbers are added or subtracted..

Working in groups:This activity lends itself to paired discussion work and small group work and, by encouraging students to work collaboratively, it is likely that you will allow

themaccess to more of the key processes than if they were to work individually.

Assessment:You may wish to consider how you will assess the task and how you will record your assessment. This could include developing the assessment criteria withyour class. You might choose to focus on the content objectives or on the process objectives. You might decide that this activity lends itself to comment-onlymarking or to student self-assessment.

If you use the APP model of assessment then you might use this activity to help you in building a picture of your students’ understandingAssessment criteria to focus on might be: • search for a solution by trying out ideas of their own (using and applying mathematics level 4)• solve simple problems involving ordering, adding, subtracting negative numbers in context (calculating level 5).

Probing questions:These might include:• can you draw a picture to show what’s happening in the box?• will [adding positives, taking positives, adding negatives, taking negatives] make the total more positive or more negative? By how much?• if I needed to make the total charge two more negative, how could I do it? What if I don’t have any more negative particles to add?• what other operation gives the same effect as taking out three negatives?• if the charge in the box is -5, how many of each particle could there be?• the scientist has a box with a charge of -4 and adds six negative particles to it. How would you record this? What would be the resulting charge?• explain in words what’s happening if the scientist writes down 4 + -7. What is the resulting charge?

You will need:The PowerPoint presentation. There are six slides:

The first two slides set the scene, introducing the idea that matter and antimatter destroy each other.

The third slide gives students a situation and asks them to predict the total charge when matter and antimatter meet.

The fourth slide gives a catalyst for students to discuss different ways of achieving the same result (e.g. that subtracting

negative two is the same as adding positive two).

The final two slides pose two situations and ask students to reason the result of adding or taking particles out of the box and to construct their own way of recording what happens.