Ian Cisternas - Photosynthesis Analysis.pdf - Name: Date:...

Name: _____________________________ Date: _____________ Class: ____________
Lab Biology
Unit 5 - Matter & Energy for Life
Intro to Photosynthesis - Analysis of Evidence
Where does a plant's mass come from?
In this activity, you will analyze evidence to learn more about each of these student
hypotheses.
For each hypothesis in the cartoon below: First, identify what each student is claiming to be the
source of the mass. To do this, circle the word in each hypothesis.
Next, write a T if you think the hypothesis is true or an F if you think the hypothesis is false.
Student A Student B Student C Student D
_T____ __T___ _F____ T_____
Background: Through chemical composition analysis, the molecules and even elements can
be determined of any substance/matter. With this technology scientists now know that plants are
made up of two types of molecules: water and organic molecules (molecules in living things
made with mostly C-H-O-N).
Based on information learned in previous units, what does C-H-O-N stand for? _carbon,
hydrogen, oxygen, and
nitrogen______________________________________________________________________
_____

EVIDENCE #1 - Plant Mass vs. Total Mass: Our first question is how much of a plant’s mass
is water and how much is organic molecules. To find out, you can weigh a plant, then dry the
plant in an oven to remove all the water, and then weigh the dried plant. This table shows
representative results for a small plant. Complete the second and third columns of the table.
Weight % of plant’s
mass
Total mass of plant 5.6
grams
100%
Mass of dried plant = mass of organic molecules in plant =
biomass
1.4
grams
Mass of water in plant before it was dried
A. Do the results you calculated for Evidence #1 support any of the student hypotheses
above? Why or why not?