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Uploaded:2015-04-09
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Have you ever seen a magic trick where one thing changes to another thing? Well, that's nothing compared to what plants can do through a process called photosynthesis. In this episode, Sabrina talks about how photosynthesis works!

This first series is based on 5th grade science. We're super excited and hope you enjoy Crash Course Kids!

///Standards Used in This Video///
5-PS3-1. Use models to describe that energy in animals’ food (used for body repair, growth, motion, and to maintain body warmth) was once energy from the sun.

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Credits...

Executive Producers: John & Hank Green
Producer & Editor: Nicholas Jenkins
Cinematographer & Director: Michael Aranda
Host: Sabrina Cruz
Script Supervisor: Mickie Halpern
Writer: Jen Szymanski
Consultant: Shelby Alinsky
Script Editor: Blake de Pastino

Thought Cafe Team:
Stephanie Bailis
Cody Brown
Suzanna Brusikiewicz
Jonathan Corbiere
Nick Counter
Kelsey Heinrichs
Jack Kenedy
Corey MacDonald
Tyler Sammy
Nikkie Stinchcombe
James Tuer
Adam Winnik
(Intro)

(0:10)
Have you ever seen someone do a presto change-o trick? Some of the living things that you see everyday also do a pretty impressive changing act, no props required.

You probably already know that all living things need energy to grow and to survive and that plants are one of the few kinds of living things that can change light energy into chemical energy in the form of sugar.

But if it's not magic, then how do they do it? How do plants change light energy into chemical energy?

The answer - a word that kind of sounds like a magic spell, Photosynthesis.

Let's take a closer look at a plant to track down exactly what photosynthesis is all about. While we're exploring, we'll use a diagram to show what's going on inside.

Ever wonder why plants are green? Their cells contain a green colored chemical called chlorophyll. The chlorophyll is found in special mini containers called chloroplast.

When the sun shines on a plant's leaf, the green chlorophyll inside the cell grabs that light energy and uses it to change water and a gas called carbon dioxide into sugar.

Another gas, oxygen, is released back into the air, so stop, take a deep breath and thank a plant.

Why? Because most of the oxygen in the air around you right now is there because of photosynthesis. And this is really convenient because you, me and all other animals on Earth count on that oxygen to breath. Plus, bonus, since animals can't do photosynthesis, they can get energy by eating the plants and all of the delicious sugar they made during photosynthesis. It's a two for one. 

So how do we know that light is what's so important for photosynthesis.

Well, we can tell by doing an experiment using two plants as a model.

These are both the same type of plant with the same amount of soil. We'll put one plant in the dark for a few days and one in the light, making sure that both plants get the same amount of water and are kept at the same temperature, just to keep things fair. Now, what do you think will happen?

Right! the one that's been in the dark sure doesn't look too healthy. That's because there wasn't any sunlight to drive photosynthesis. Without photosynthesis, the plant can't make any sugar. No sugar means no energy and no energy means a droopy tired looking plant. 

So, photosynthesis is how plants use a chemical called chlorophyll to capture the Sun's energy. They use this energy to change carbon dioxide and water to chemical energy in the form of sugar. This sugar along with the oxygen that's released is used by animals to survive and that's a change we can all live with.