4A30.XX Cool Plastic Rulers. Difficulty Moderate: Setup Time Short: Visibility Moderate: Appeal ★★★ Education ★★ Concepts. Thermal expansion and contraction. Overview. One ruler is cooled to liquid ...

BE QUICK. The cooled ruler heats up quickly. Occasionally the cooled ruler will curl or bend. If this happens, hold the ruler flat on the overhead. Cautions: Liquid nitrogen can cause severe burns and ...