One reason for following directions carefully and for keeping records of one's work is to provide information on what might have caused the differences. Scientists' explanations about what happens in the world come partly from what they observe, partly from what they think. Sometimes scientists have different explanations for the same set of observations. That usually leads to their making more observations to resolve the differences. Scientists do not pay much attention to claims about how something they know about works unless the claims are backed up with evidence that can be confirmed and with a logical argument.
Students investigate four water samples.
They use direct observation and hardness indicators to understand its unique properties. They also observe and study the process of evaporation. They collect water from local sources and examine its properties. During the activity, students develop the concept of water quality. Clear communication is an essential part of doing science.