Kettle – I will boil the kettle to an appropriate temperature which will kill any productions in the leaf.
3 Beakers – The beakers act as container and the beaker also helps me to measure the amount of water.
9 Test tubes – This will measure the amount of different substances on an accurate scale.
Ethanol – This will remove chlorophyll from the leaf and destroy the waxy layer (cuticle) on the leaf’s surface.
Petri dish – This will provide the surface area for the reaction to take place. I t also acts as a store to keep the leaf on.
Cold water
Iodine –This will react with starch to indicate the colour change in the leaf. The iodine will indicate whether there is starch present in the leaf.
Water – The water will be provided from the tap, this water will be boiled in the kettle. This hot water will also be used to sterilise all the apparatus after.
Stands -
3 Lights – to ensure that the lamps don’t become over used because this could lead to heat.
Clamp – The clamp will hold the lamp, this will make sure that the light is shone evenly on the leaf.
Forceps – This instrument will be used to pick up and move the leaf from A to B.
Safety Glasses – This protect my eye from any corrosive substances I may come across while doing my experiment.
Plan:
Before I started my experiment all leafs were left untouched.
Step 1: Set up all apparatus needed. Previously the plant was left in a normal room temperature for 24 hours.
Step 2: Boil the water for the appropriate time. Pour 20 cm of water in a beaker, after this remove four leafs at random from a plant (preferably the greenest) then use forceps to hold the leaf and transfer it into the beaker containing 20 cm of hot water..
Step 3: Add approximately 5 cm of ethanol in each test tube and place each of the leaves in it. The ethanol will destroy the chlorophyll on the surface area of the leaf.
Step 4: Place each of the test tubes in a beaker filled with boiled water for 2 minutes
Step 5: After the 2 minutes remove each of the plants from the ethanol and thoroughly cleanse the leaf with cold water and forceps. This will prevent the leaf reacting with iodine that is going to be added.
Step 6: Spread each on a Petri dish and add the required amount of iodine needed to change the colour of the leaf.
My range of readings will be ranged from 10-30cm.
Background Theory
We can write the overall reaction of this process as:
6H2O + 6CO2 ----------> C6H12O6+ 6O2
Photosynthesis:
Photosynthesis is the process which produces food for plants. This food is stored in the plant as glucose; this food is then converted into starch. Before this process happens plants need certain criteria for them to produce starch. The most important criteria are light energy from the sun. Chlorophyll is a green found in .The chlorophyll absorbs the light energy from the sunlight combining with carbon dioxide and water to produce glucose.The glucose can them be used for various activies to help sustain the plant.The main prurpose is to use the glucose and convert it into starch which can then be used for food purposes.
The things that affect the rate of:
1.The amount of sunlight
2.The amount of carbon dioxide
3.The temperature
4.Texture and condtionof soil
5.The amount if water
Light is with a if the intensity increases then the light will relasease more photons.
Leaves and Leaf Structure
Plants are the only photosynthetic organisms to have (and not all plants have leaves). A leaf may be viewed as a solar collector crammed full of photosynthetic cells.
The raw materials of photosynthesis, water and carbon dioxide, enter the cells of the leaf, and the products of photosynthesis, sugar and oxygen, leave the leaf.
Water enters the root and is transported up to the leaves through specialized plant cells known as . Land plants must guard against drying out and so have evolved specialized structures known as stomata to allow gas to enter and leave the leaf. Carbon dioxide cannot pass through the protective waxy layer covering the leaf (cuticle), but it can enter the leaf through an opening (the stoma; flanked by two guard cells. Likewise, oxygen produced during photosynthesis can only pass out of the leaf through the opened stomata. Unfortunately for the plant, while these gases are moving between the inside and outside of the leaf, a great deal water is also lost. Cottonwood trees, for example, will lose 100 gallons of water per hour during hot desert days.
The loss of water from the stomata will cause the prduction of starch to reducethis is because the water needed for photosynthesis to occur is being lost.
Light Reactions
There are 2 light reactions:
In the Light Dependent Processes (Light Reactions) light strikes chlorophyll a in such a way as to excite electrons to a higher energy state. In a series of reactions the energy is converted (along an process) into and . Water is split in the process, releasing oxygen as a by-product of the reaction. The ATP and NADPH are used to make C-C bonds in the Light Independent Process (Dark Reactions).
In the Light Independent Process, carbon dioxide from the atmosphere (or water for aquatic/marine organisms) is captured and modified by the addition of Hydrogen to form carbohydrates (general formula of carbohydrates is [CH2O] n). The incorporation of carbon dioxide into organic compounds is known as carbon fixation. The energy for this comes from the first phase of the photosynthetic process.
What is starch?
Starch is a which is in ; it is used by as a way to store excess .
Test for starch:
Starch solution is used to test for elemental . A blue/black color indicates the presence of in starch solution. The details of this reaction are not yet fully known, but it is thought that the fits inside the coils of . A 0.3% w/w solution is the standard concentration for a dilute starch indicator solution. It is made by adding 4 grams of soluble starch to 1 litre of heated water; the solution is cooled before use (starch-iodine complex becomes unstable at temperatures above 35°C). This complex is often used in titrations: in presence of an the solution turns blue, in presence of blue color disappears because I5− ions break up into iodine and iodide.
Under the , starch grains show a distinctive effect (also known as 'extinction cross' and birefringence) under .
How do the factors affect starch?
The concentration of C02 affects the amount of starch produced in the leaf because only 0.03% of the atmosphere contains C02, if there’s not enough C02 then the plant can’t photosynthesize therefore cannot make starch.
The temperature affects the enzymes that control the chemical reactions of photosynthesis, if the temperature is too high it will kill the enzymes vice versa. The temperature of the room was 22 c.
The light affects the amount of starch produced because the chlorophyll uses light energy to perform photosynthesis. Nutrients in the leaf such as potassium are important because it helps enzymes in photosynthesis. Magnesium affects the amount of starched produced because Magnesium makes chlorophyll because without chlorophyll photosynthesis wouldn’t happen, minerals such as phosphates and Nitrates also affect the amount of starch produced.
Using a reasonable amount of iodine to react with the starch will cause the leaf to indicate the colour change and show how much starch is present. If I use less than needed than the colour might not change when it’s supposed to, this would lead me to obtaining inaccurate results. The amount of ethanol used will play a major impact, if ethanol removes chlorophyll from a leaf, a smaller amount of ethanol might not be
able to eliminate any chlorophyll present in the leaf. This will make my results anomalous and would make my whole investigation wrong. The amount o time the leaf is killed by boiling water. The boiling water is intended to stop any chemical reactions taking place.
Obtaining Evidence:
1 2
3 Average
Analysis
At the measurement of 10 cm the colour of the ph was black for all of my 3 reading. I believe it was black because no starch was produced. The light caused the energy to change into heat which killed the enzymes. The light is so close to the leaf that 100% of the lights energy will travel directly to the leaf. When the light is absorbed the chlorophyll will not be able to synthesise water and carbon dioxide because the cells will not be able to coup with the heat causing them to be damaged.
At the measurement of 20 cm the colour of the ph was black/green for readings 2and 3 because the height of the lamp had been increased causing some of the light energy to slow down because the distance the light had to travel is longer causing particles in the air to collide with the light making the light slow down in speed. For readings 1 the measurement was 20 seconds this result varied from all the other readings under the same measurement. I believe this happened because the lamp was used for the first time meaning it was not over used which could of lead to heat causing it go black/green instead of it going light purple. I also believe this because in my preliminary I had the same problem occurring.
At the measurement of 30 cm, readings 1 and 2 produced a ph that made the iodine change to green. I believe this happened because the lamp was cooled for a longer interval between 1 and 2 .This made the lamp more refreshed and more reliable
Evaluation:
My results are reliable simply because I have had experience from my preliminary experiment therefore any mistakes that I had made in my preliminary could be corrected therefore would of given me accurate results. There were some anomalous because of mistakes made. I used didn’t let my lamp cool down which made my lamp hot when used for a long duration.
Before pouring the water onto leaf I believe that I left the water to long before pouring it onto the leaf. My timing skills were poor due to me forgetting to start the timer.
There are many things I could of done to improve my reliability of results I could of timed how long the plant was kept under the light because my plants were not kept under light for exactly 24hrs I came into the room about 22hrs10mins therefore my plant did not get the maximum amount of time therefore my results could of improved
There was less C02 because there were only plants in the room and they were taking in all the C02 so as time went on less C02 was in the atmosphere this would slow down the rate of photosynthesis produced. I could of took more leafs from various plants in different whether climates such as rain, heat to see whether the light or climate affected the amount of starch produced.
I could have used cold water and warm water to help me identify whether the light affected the starch production to see whether this method would kill the leaf as the hot water did. . I never weighed my leafs before and after the experiment, I should of done this because if a small fragment of starch was gained or lost I wouldn’t not be able to tell whether it contains starch because the ph would of not been as accurate. I could of used different types of light such as sun, torch. The lamp could have of been over used, this could of caused a dimmer light to be emitted.
I could have tested for the oxygen produced by relighting a glowing splint. I would have been able to do this if I done my experiment in a more controlled area. could of heated the flame for a very quick duration than cool it down to ensure that all starch produced was broken down
I was not accessed to some of the equipment I needed due to a lack of resources that were provided to me. I believe that if my mistakes were corrected I would have met my hypothesis more accurately.
Conclusion:
Overall I believe that my results were unprofessional because I didn’t have enough time to prepare. I was also not provided with accurate instruments which would help me to record more professional results. One thing I am happy with is that my results reflect my hypothesis
Bibliography:
Miss Chahal (Class teacher)
Gcp Book
Partner (Anwar)
