Your experiment will produce data that you will analyze to see if your hypothesis was accurate. Your observations are data. Data needs to measured carefully and described specifically.
Be ready to record and measure the changes you observe using the methods described in your procedure. Have your materials for data collection organized before you start your experiment. For example, you might create tables in a notebook that will help you neatly record details such as the date, starting time, ending time, and duration of each step in your experiment. Familiarize yourself with the International System of Units (SI units) needed for measuring. Having your materials for data collection ready before you start will help you remember to record the same information for each observation. It will also make it easier to compile your data.