3/17/14 The Movement Ques4on Plants Lesson 2, Ac4vity 2: Modeling Photosynthesis Answering the Three Ques4ons for plants in the light. Which atoms and molecules move so that plants can do photosynthesis? water carbon dioxide Where are atoms moving from? Where are atoms moving to? How do glucose water, carbon dioxide and oxygen move for a plant leaf to photosynthesize? water oxygen glucose Plants make glucose from carbon dioxide and water in their leaves. carbon dioxide oxygen glucose What happens inside the leaf cell as it photosynthesizes? Chemical change 1 3/17/14 What is Photosynthesis? •  Photosynthesis is the secret of plant growth. •  Plants do photosynthesis so they can grow (gain biomass). Photosynthesis happens when light energy from the sun, carbon dioxide, and water are used to make sugar and oxygen. (the sugar is then used to build the plant’s mass; the O2 is released as waste) Rules of Molecular Bonding Reminder: •  Atoms in stable molecules always have a certain number of bonds to other atoms: –  Carbon: 4 bonds –  Oxygen: 2 bonds –  Hydrogen: 1 bond •  This means that if you have a carbon atom, for example, all 4 of its “prongs” should be aTached to other atoms. There should not be empty prongs. •  Oxygen atoms do NOT bond to other oxygen atoms if they can bond to carbon or hydrogen instead. The Carbon Ques6on: What is happening to carbon atoms? What molecules are carbon atoms in before photosynthesis? How are the atoms rearranged into new molecules during photosynthesis? The Energy Ques6on: What is happening to energy? What forms of energy are involved in photosynthesis? How is energy changing from one form to another during photosynthesis? Using your poster and modeling kits, make a model of how maTer and energy are transformed during photosynthesis. Making the Reactant Molecules: Carbon Dioxide and Water Photosynthesis occurs when plants combine carbon dioxide (CO2) and water (H2O) to produce glucose (C6H12O6) and oxygen (O2). Show how this can happen: 1.  Get the atoms you will need to make your molecules. Can you figure out from the formula for sugar how many C, H, and O atoms you will need? 2. 
3. 
4. 
a.  You will need 6 carbon atoms to make one sugar molecule. How many CO2 molecules will you need to make for the reactants? b.  You will need 12 hydrogen atoms to make one sugar molecule. How many H2O molecules will you need to make for the reactants? Use the bonds to make models of carbon dioxide (CO2) and water (H2O). Remember that CO2 has double bonds. There are no high-­‐energy bonds (C-­‐C and C-­‐H) in carbon dioxide or water. Add 12 twist 4es to the reactants to represent light energy. Compare your molecules to the pictures on the next slide. Are they the same? 2 3/17/14 Photo of reactant molecules: CO2 (carbon dioxide) and H2O (water) Start by making the molecules of the reactants and energy units of light. Put them on the reactants side, then rearrange the atoms and energy units to show the products. Carbon dioxide Water When you’re done, what will it look like? Arrange your atoms so that the water and carbon dioxide are transformed to glucose and oxygen. Chemical change Heat Energy Work or Mo6on Energy Products Reactants Remember: Atoms last forever (so you can rearrange atoms into new molecules, but can’t add or subtract atoms). Energy lasts forever (so you can change forms of energy, but energy units can’t appear or go away). 13 Making the Product Molecules: Glucose and Oxygen Photo of product molecules: H6C12O6 (sugar) and O2 (oxygen) Start by making the molecules and energy units of the reactants and pubng them on the reactants side, then rearrange the atoms and energy units to show the products. . Photosynthesis occurs when carbon dioxide (CO2) and water (H2O) react to produce glucose (C6H12O6) and oxygen (O2). Show how this can happen: 1.  Break the bonds in the reactant molecules and recombine the atoms into sugar (C6H12O6) and oxygen (O2). How many oxygen molecules can you make? 2.  Iden4fy the high-­‐energy bonds (C-­‐C and C-­‐H) by pubng twist 4es on them. How many high energy bonds does a molecule of sugar have? Where does the energy for those bonds come from? 3.  Compare your molecules to the pictures on the next slide. Are they the same? Glucose with chemical energy Chemical change Oxygen Reactants Products Remember: Atoms last forever (so you can rearrange atoms into new molecules, but can’t add or subtract atoms). Energy lasts forever (so you can change forms of energy, but energy units can’t appear or go away). 16 Wri4ng a Chemical Equa4on Comparing photos of reactant and product molecules Compare the atoms and energy units on the reactant and products sides. . Glucose with chemical energy Carbon dioxide Water Chemical change Heat Energy Work or Mo6on Energy Reactants Oxygen Products Remember: Atoms last forever (so you can rearrange atoms into new molecules, but can’t add or subtract atoms). Energy lasts forever (so you can change forms of energy, but energy units can’t appear or go away). •  Wri4ng in symbols: Chemists use an arrow to show how reactants change into products: [reactant molecule formulas] à [product molecule formulas] •  Saying in words: Chemists read the arrow as “yield” or “yields”: [reactant molecule names] yield(s) [product molecule names] •  Equa4ons must be balanced: Atoms last forever, so reactant and product molecules must have the same number of each kind of atom. •  Try it: can you write a balanced chemical equa4on to show the chemical change for photosynthesis? 17 3 3/17/14 Chemical Equa4on for Photosynthesis What happens
to atoms and energy
in photosynthesis?
Carbon Dioxide 6H2O + 6CO2 à C6H12O6 + 6O2 (in words: water and carbon dioxide yield glucose and oxygen) Glucose Chemical change Reactants Water Products Oxygen Light energy 19 20 What happens
to carbon atoms
in photosynthesis?
What happens to oxygen
and hydrogen atoms in
photosynthesis?
Carbon Dioxide Carbon Dioxide Glucose Chemical change Glucose Reactants Chemical change Water Water Products Light energy Reactants Products Carbon atoms in
carbon dioxide
become part of
glucose molecules.
Oxygen Light energy Oxygen and hydrogen atoms become part of glucose and oxygen gas molecules.
Oxygen 21 22 What happens
to light energy
in photosynthesis?
What happens
to atoms and energy
in photosynthesis?
Carbon Dioxide Carbon Dioxide Glucose Chemical change Glucose Reactants Chemical change Water Water Products Light energy Reactants Products Light energy is
transformed into
chemical energy.
Oxygen Light energy 23 Atoms last forever!
Energy lasts
forever!
Oxygen 24 4 3/17/14 How can we answer the Carbon Ques4on and the Energy Ques4ons now? The Carbon and Energy Ques4ons •  Carbon: carbon atoms move from CO2 molecules in the air (inorganic) to C6H12O6 molecules in the plant (organic). The Carbon Ques6on: What is happening to carbon atoms? What molecules are carbon atoms in before photosynthesis? How are the atoms rearranged into new molecules during photosynthesis? The Energy Ques6on: What is happening to chemical energy? •  Energy: energy is transformed from light energy into chemical energy in the high-­‐
energy (C-­‐C and C-­‐H) bonds of the glucose molecule. What forms of energy are involved in photosynthesis? How is energy changing from one form to another during photosynthesis? The Three Ques6ons for plants in the light Where are atoms moving from? What molecules are carbon atoms in before the change? What other molecules are involved? Where are atoms moving to? Chemical change What molecules are carbon atoms in aker the change? What other molecules are produced? What forms of energy are in the What forms of energy are in the reactants? products? Remember: Atoms last forever and Energy lasts forever 27 5