1. Trapping Energy
Interest Grabber
Section 8-2
Have you ever used a solar-powered calculator? No matter where you go, as long as you have a light source, the calculator works. You never have to put batteries in it.

2. Interest Grabber continued
1. A solar-powered calculator uses solar cells that are found in rows along the top of the calculator. Into what kind of energy is the light energy converted so that the calculator works?
2. Recall that plants use light energy from the sun to make food. Into what kind of energy is the light energy converted by plants?
3. Most plants, no matter what size or shape they are, have some parts that are green. Which parts of a plant are usually green?
4. What does the green color have to do with the plant’s ability to convert light energy into the energy found in the food it makes?

3. Photosynthesis: An Overview
Chapter 8.2
Photosynthesis: An Overview

4. Photosynthesis
Plants use energy of sunlight to convert water and carbon dioxide into high-energy carbohydrates – sugars and starches – and oxygen
Oxygen is considered a waste product of photosynthesis

5. Photosynthesis: Reactants and Products
Section 8-2
Light Energy
Chloroplast
CO2 + H2O
Sugars + O2

6. Jan van Helmont
Experiment  find out if plants grew by taking material out of the soil
Determined mass of dry soil and seedling
Watered seed regularly
After 5 years – mass of tree changed, while mass of soil remained unchanged
Concluded that increase in mass was due to the water
Accounts for “hydrate” in carbohydrate
Carbon from carbon dioxide accounts for “carbo” in carbohydrate

7. Van Helmont’s Experiment

8. Joseph Priestly Experimented with fire in a jar with a sprig of mint
Fire needed oxygen to keep burning
Putting a jar over the flame put the fire out
If mint was placed in jar, fire would keep burning
Concluded that plants gave off oxygen

9. Summary:
burning candle + bell jar →  candle goes out + add a mint plant  →  candle can be relit
mouse + bell jar →  dead mouse + add a mint plant →  mouse lives
Questions:
1. Why did the candle burn out when placed under bell jar?
2. Why could the candle be relit after allowing it growth with a mint plant?
3. Why does a mouse die when it is placed under a bell jar?
4. Why was the mouse able to survive when placed in the jar with a mint plant?

10. Jan Ingenhousz
Showed that the experiment done by Priestly only occurred if the plant was in light
Light is needed to produce oxygen
Put all three scientists together:
In the presence of light, plants transform carbon dioxide and water into carbohydrates, and they also release oxygen

11. Photosynthesis Equation
6CO H2O LIGHT C6H12O O2

12. Light Light is a form of energy that travels in waves
White light is a mixture of light of different wavelengths
When broken down, white light produces the visible spectrum (400nm – 750 nm)
ROY G. BIV
Red, orange, yellow, green, blue, indigo, violet
Red has a longer wavelength than violet

13. Pigments of Plants Pigments – light absorbing pigments
Because light is energy – energy is absorbed by the pigments
Their electrons get excited to a higher energy level
Chlorophyll – main light absorbing pigment of plants
Two types: chlorophyll a and chlorophyll b
Absorbs light in the blue-violet and red regions; reflects green light

15. Chlorophyll a and Chlorophyll b
Absorption of Light by
Chlorophyll a and Chlorophyll b
1. How does the color spectrum at the bottom relate to the graph?
2. In what region of the spectrum does chlorophyll a absorb light best?
3. In what region of the spectrum does chlorophyll b absorb light best?
4. In what region of the spectrum do neither types of chlorophyll absorb light well at?
Chlorophyll b
Chlorophyll a V B G Y O R

16. Pigments of Plants
Carotenoids – red, orange, and yellow pigments in plants
Absorb light in the other regions of the spectrum
Leaves change color because the chlorophyll molecules fade away and the carotenoids are left over

17. Photosynthesis Video
Photosynthesis