Use any word processing document (Pages, Word, etc.) to collect your data. You may be doing any one or more of the following during the experimentation part of this project:

Collecting temperature vs. time
Recording observations (things you see, hear, etc.)
Recording observations during specific time intervals
Making lists
Keeping tallies

Use a method that works the best for your experiment. See the scientific method review in the first Moodle block for more ideas.