• push-button, screw-apart ballpoint pens, one per student; see note below
• Click Pen Investigation Worksheet
• Click Pen Diagram Worksheet (a cross-sectional diagram)
• Rubric for Performance Assessment
• assorted other pens and pencils, for comparison

Note about pens: It is best to get retractable "click" pens that twist or unscrew apart into separate barrels so the inner pieces can easily fall out, so students do not have to break the casing. One source: BIC Clear Click^TM pens for 73 cents each from Specialty Promotions Unlimited, 1-800-539-3751 or http://www.bicspecials.com. The Econo-Pen is cheaper (SM-103 ECONO-PEN).