Setting up…

Thermometer needle: watch where it stopsSet pointer: your guessHotplate, beaker, standA 1000 W hotplate under 500 mL of water at 20 °C. About 55% of the plate's power reaches the water, so on high it takes about 6 minutes to reach the boil; this figure runs 30 times faster. At 100 °C every joule goes into turning water to steam (2.26 MJ for each kilogram), so the needle stops climbing, and turning the plate up only boils the water away faster: 6 g a minute on medium, 12 g on high.