STUDENTS WILL BE ABLE TO:

1. DEFINE THE TERM, HALF-LIFE.

2. DISTINGUISH BETWEEN PARENT AND DAUGHTER ELEMENTS.

3. USE THIS MODEL TO DEMONSTRATE HALF-LIFE TO OTHERS.

MATERIALS NEEDED: CLOCK OR WATCH WITH SECOND HAND, SHEET OF RULED NOTEBOOK PAPER, SCISSORS.

ANTICIPATORY SET: DISCUSS THE RADIOACTIVE DECAY OF URANIUM-238 AS A PARENT ELEMENT AND HOW IT BECOMES THE DAUGHTER ELEMENT, LEAD-206. DISCUSS THE TERM, HALF-LIFE AND WHAT IT MEANS IN TERMS OF THE RADIOACTIVE DECAY OF U-238. THIS INTRODUCTION LEADS TO A SIMPLE EXERCISE WHICH DEMONSTRATES THE CONCEPT OF HALF-LIFE.

PROCEDURE:

1. RECORD THE TIME.

2. WAIT ONE MINUTE, THEN CUT THE PAPER IN HALF. SELECT ONE PIECE, AND SET THE OTHER PIECE ASIDE.

3. WAIT ONE MINUTE, THEN CUT THE SELECTED PIECE IN HALF. SELECT ONE PIECE, THEN SET THE OTHER PIECE ASIDE.

4. REPEAT STEP 3 UNTIL 9 ONE-MINUTE INTERVALS HAVE ELAPSED.

QUESTIONS TO CONSIDER:

1. IN TERMS OF RADIOACTIVE DECAY, WHAT DOES THE WHOLE PIECE OF PAPER USED IN THIS INVESTIGATION REPRESENT?

2. WHAT DO THE PIECES OF PAPER THAT YOU SET ASIDE IN EACH STEP REPRESENT?

3. WHAT IS THE HALF-LIFE OF YOUR ELEMENT?

4. WHAT FRACTION OF YOUR PAPER WAS LEFT AFTER THE FIRST THREE INTERVALS? SIX INTERVALS?

5. WHAT TWO FACTORS IN YOUR MODEL MUST REMAIN CONSTANT FOR YOUR MODEL TO BE ACCURATE?

CLOSURE: HOW DOES THIS MODEL REPRESENT RADIOACTIVE DECAY?

EXTENSION:

1. WHAT IS CARBON DATING AND HOW IS THE IDEA OF RADIOACTIVE DECAY USED IN THAT PROCESS?

2. WHAT ARE THE HALF-LIVES OF SOME RADIOACTIVE ELEMENTS?

ASSESSMENT:

1. CAN STUDENTS ANSWER THE FIVE QUESTIONS TO CONSIDER?

2. CAN STUDENTS DEMONSTRATE THIS ACTIVITY AS A MODEL OF RADIOACTIVE DECAY?

E-Mail

ROGER WISE

!