Photosynthesis
Science
Unit: Plant nutrition and photosynthesis
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Outcome
I can identify the reactants and products of photosynthesis and write a
word summary of the process.
Keywords
producer
chemical reaction
photosynthesis
carbon dioxide
glucose
Keywords
A producer is an organism that makes its own food.
In a chemical reaction, substances are broken down and react to form new
substances.
Photosynthesis is a series of chemical reactions by which producers make their
own food.
Carbon dioxide is a compound made of carbon and oxygen that is a gas at room
temperature and a reactant in photosynthesis.
Glucose is a sugar (carbohydrate) produced by photosynthesis.
Lesson outline
Photosynthesis
How producers make their own food
The reactants and products of photosynthesis
How producers make their own food
Explanation
Plants and other producers make
their own food.
The food is made by a process called
photosynthesis.
This process happens in the leaves
and other parts of the plant that are
above the ground.
leaf of a maple tree
How producers make their own food
Photosynthesis can only happen when there is
light.
photosynthesis
light
to make
What other words do you know that contain ‘photo’?
Explanation
How producers make their own food
Check
True or false?
Photosynthesis happens in plant roots.
T
True
F
False
Justify your answer
A
Photosynthesis happens in plant leaves when there is light.
B
Photosynthesis happens in all parts of a plant.
How producers make their own food
Explanation
Leaves are made up of cells.
Photosynthesis takes place inside the cells.
leaf of a maple tree
leaf cells seen through a microscope
How producers make their own food
Check
Match the one correct start of the sentence… …to the one correct end
of the sentence to make one single sentence.
Plant food is made
between plant cells…
…by the process of cellular
respiration.
Plant food is made from
plant cells…
…by the process of
photosynthesis.
Plant food is made inside
plant cells…
…by the process of
digestion.
How producers make their own food
Explanation
Photosynthesis needs light.
light
Light transfers energy from the
light source to the leaf cells.
light is absorbed
by leaves
This provides the energy needed for
photosynthesis to take place.
How producers make their own food
Which statement about light and photosynthesis is true?
A
Light creates cells for photosynthesis.
B
Light is made by photosynthesis.
C
Light provides the energy for photosynthesis.
Check
Task 1
How producers make their own food
Practice
Izzy has had a houseplant for a long time.
● It is still very small.
● She keeps it in a dim corner of the room, far
away from the window.
Izzy’s houseplant
Izzy decides to move the plant so that it is next to the window.
Explain why this will help the plant to grow bigger.
Task 1
How producers make their own food
Putting the houseplant next to the window will help the
plant to grow bigger because:
● It will get more light from the Sun.
● Light transfers energy from the Sun to the plant’s
leaf cells.
● This provides energy for photosynthesis.
● Photosynthesis makes the plant’s food.
● This food is used as:
– a source of materials for growth
– a source of energy for other life processes.
Feedback
Lesson outline
Photosynthesis
How producers make their own food
The reactants and products of photosynthesis
The reactants and products of photosynthesis
Photosynthesis is a series of chemical reactions that happen inside leaf cells.
leaf cells seen through a microscope
During chemical reactions:
● one or more substances are broken down - these are the reactants
● one or more new substances are made - these are the products.
Explanation
The reactants and products of photosynthesis
Explanation
Like any chemical process, photosynthesis has reactants and products.
light
glucose
carbon
dioxide gas
reactants
water
oxygen
gas
products
The reactants and products of photosynthesis
Explanation
Photosynthesis is not just one chemical reaction.
It’s a series of chemical reactions that happen inside plant cells.
But it is useful to remember a word summary of the reactants and products:
water + carbon dioxide
reactants
glucose + oxygen
products
The reactants and products of photosynthesis
Check
Complete the word summary for photosynthesis.
carbon dioxide
+
water
glucose
+
oxygen
The reactants and products of photosynthesis
water + carbon dioxide
Explanation
glucose + oxygen
One of the reactants of photosynthesis is
water.
Plants take in water for
photosynthesis through
their roots.
The water is transported to the
leaves for photosynthesis.
water
The reactants and products of photosynthesis
water + carbon dioxide
Explanation
glucose + oxygen
One of the reactants of photosynthesis is
carbon dioxide.
Plants take in carbon dioxide gas for
photosynthesis from the air, through their
leaves.
carbon
dioxide
gas
The reactants and products of photosynthesis
water + carbon dioxide
Explanation
glucose + oxygen
One of the products of photosynthesis is
glucose.
Glucose is a type of sugar, which is a
carbohydrate. It is the plant’s food.
The glucose is transported to all parts of the
plant where it is used:
● as a source of energy
● as a source of materials to make new cells
and tissues for growth.
glucose is
made inside
leaf cells
glucose is
transported to
all parts of the
plant
The reactants and products of photosynthesis
water + carbon dioxide
Explanation
glucose + oxygen
One of the products of photosynthesis is
oxygen.
Plants release this oxygen into the air from their
leaves.
oxygen
gas
The reactants and products of photosynthesis
Check
Match each substance to its role in photosynthesis.
substance
carbon dioxide
glucose
oxygen
water
role
made by
photosynthesis
used for
photosynthesis
made by
photosynthesis
used for
photosynthesis
The reactants and products of photosynthesis
Check
Match each substance to the correct description.
substance
description
carbon
dioxide
glucose
oxygen
water
reactant
product
reactant
product
The reactants and products of photosynthesis
water + carbon dioxide
Explanation
glucose + oxygen
Photosynthesis needs light.
light
However:
● Light is not a substance.
● Light is not a chemical reactant in
photosynthesis.
light is absorbed
by leaves
● Light is not turned into a product during
photosynthesis.
Light provides the energy needed for the chemical reactions of
photosynthesis to take place.
The reactants and products of photosynthesis
water + carbon dioxide
Explanation
glucose + oxygen
Glucose is a type of sugar.
A bag of sugar from the shop has a
mass of 1 kilogram (1 kg).
How many bags (kilograms) of sugar do you
think a large tree can make in one sunny
day?
The reactants and products of photosynthesis
water + carbon dioxide
glucose + oxygen
A large tree can produce around 90 kg of glucose
from photosynthesis in one day.
Most of the mass of that glucose is made up of
carbon atoms.
All of those carbon atoms came from carbon
dioxide gas from the air!
Explanation
The reactants and products of photosynthesis
Complete the sentences about photosynthesis.
carbon from
dioxide
The reactants of photosynthesis are ________________
the air
and __________ from the water
soil.
Photosynthesis makes a type of carbohydrate called __________ that
glucose
the plant
uses to grow bigger.
Most of the mass of this carbohydrate is made up of __________ atoms,
carbon
which
were taken in from the air.
Check
Task 2
The reactants and products of photosynthesis
Practice
Lucas buys a small plant in a pot.
● He keeps the plant in a sunny spot.
● He waters the plant whenever the soil is dry.
After 4 months the plant is much bigger.
4 months
later
To do:
1. Write down what the plant has taken in to enable it to grow.
2. After 4 months the mass of the plant had increased, but the mass of the soil was
the same as it was at the start. Explain why.
Task 2
The reactants and products of photosynthesis
1. Write down what the plant has taken in to enable it to grow.
The plant took in water (from the soil) and carbon dioxide (from the air) for
photosynthesis. The plant also took in light to provide energy for photosynthesis.
2.
After 4 months the mass of the plant had increased, but the mass of the soil was
the same as it was at the start. Explain why.
The mass of the plant increased because it used carbohydrate from photosynthesis
to make new cells and tissues. Most of the mass of this carbohydrate came from
carbon dioxide from the air. The plant took in water from the soil, but this water
was replaced so the mass of soil didn’t decrease.
Feedback
Summary
Photosynthesis
● Producers make their own food using a process called photosynthesis.
● Photosynthesis can only happen when there is light.
● Photosynthesis is a series of chemical reactions that take place inside
plant cells.
● The reactants of photosynthesis are water and carbon dioxide.
● The products are oxygen and glucose (a carbohydrate).
● A word summary of the reactants and products of photosynthesis is:
water + carbon dioxide
glucose + oxygen
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