The speaker claimed that if you boiled water in a microwave then cooled it and used it to water a plant then the plant would die. The girls decided to design an experiment to see if this was true, which provided a great opportunity to discuss the scientific method - they boiled water in a microwave, boiled water in a kettle and kept some as normal tap water to see what the different results would be. All the plants were the same age, from the same batch and kept in the same location (same temperature and light), all were watered at the same time with the same amount of water so their only variable was the type of water used.
The plant on the left is tap water (our control), the one in the middle is boiled kettle water (just to make sure it wasn't the boiling of the water that caused the problems) and the one on the right is boiled microwave water.
I will be honest and say this is the second time we had to run this experiment as the first time we ran it all the plants were getting smaller and we couldn't understand the results - it turned out Tulip was eating our experiment, we were using basil plants which she loves to eat with tomatoes : )
Linked on Science Sunday