SciGen Teacher Dashboard
Unit M1
Small, Smaller, Smallest
Reading: Making Trees from Thin Air (Photosynthesis)
Duration: Approximately 45 minutes
Most students have heard of photosynthesis, but what they’ve learned about photosynthesis can now help them to understand chemical reactions. They will now use their new vocabulary to explain in a more precise way something they learned when they were younger.
In chemical equations, the big numbers written before the formula for a chemical show how many molecules of that chemical are used or produced in the reaction compared to the other compounds. The small numbers below and to the right of element symbols are called “subscript” numbers. The subscript numbers refer to the elements in front of them, and show how many atoms of each element go into a compound. For example, an H2O molecule has two hydrogen atoms and one oxygen atom.
No atoms are destroyed or created in a chemical reaction. Atoms are just rearranged. This sameness of mass in reactants and products in chemical reactions is called the Law of Conservation of Matter, because mass is conserved (kept the same) in chemical reactions.
One of the most important chemical reactions for life on earth takes place in plants and is called photosynthesis. Plants take in carbon dioxide (CO2) and water (H2O), and, with a little help from the sunshine, produce oxygen molecules (O2) and sugar molecules. The sugar molecules provide food to animals, but are also used by plants as basic building blocks for their own woody and leafy bodies.
This activity connects the concepts of photosynthesis and conservation of matter.
LEARNING OBJECTIVE
Students will connect the concepts of photosynthesis and conservation of matter.
Teacher Tune-ups
Teaching Notes
ACTIVITY OVERVIEW
- Discussion: Law of Conservation of Matter (10 minutes)
- Reading: photosynthesis (25 minutes)
- Critique: model of photosynthesis (10 minutes)
Discussion: Law of Conservation of Matter (10 minutes)
Ask students to think about a burning birthday candle. Have them turn and talk about whether part of the candle is "gone" once it has burned awhile.
Entertain various responses, but guide students to an understanding that matter is neither created nor destroyed, but it can change.
With the candle example the wax that has burned is now in the form of leftover wax that is liquid, soot, and gases that have drifted into the air.
The Law of Conservation of Matter is also known as the law of conservation of mass. It states that matter cannot be created or destroyed; it can only change its form.
:
Considering that trees can be huge and grow from tiny seeds, how can it be true that matter cannot be created? Where does all that matter in a big tree (or any plant) come from?
:
- Hardly any of the matter in the tree comes from the seed, but it has to come from somewhere. A lot of people think it comes from soil, but really most of the matter that makes the tree comes from molecules in the air.
Reading: photosynthesis (25 minutes)
Acknowledge that students have probably heard of photosynthesis before in elementary school, but tell them that they will be thinking about it a more advanced way now.
Assign reading and worksheet in partners or individually.
Critique: model of photosynthesis (10 minutes)
Students examine this model that shows the process of photosynthesis.
:
- Are you able to explain the model?
- If you were going to design a model of photosynthesis, how would you go about it?
- (It might be helpful to compare this animation with others, such as this one: https://www.youtube.com /watch?v=prFaSe3s9e0.)
Allow brainstorming or model development (if feasible).
BETA Version - Please send comments and corrections to info@serpinstitute.org
This project was supported by Science Sandbox, a Simons Foundation initiative dedicated to engaging everyone with the process of science.
Strategic Education Research Partnership
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info@serpinstitute.org