Thus the reactions of the light-dependent stage of photosynthesis
provide a source of reducing power (NADPH) and the universal
energy-supplying molecule ATP, with oxygen gas given off as a waste
The excited electron may instead be used to provide the reducing power
needed in the second, light-independent stage of the photosynthetic
Students will explore energy changes during chemical reactions, heat of reaction (ΔH), and the connection between energy changes and chemical changes.
Size of particles/surface area The Collision Theory The collision theory explains the rates of reaction, the rate of reaction depends on how often and how hard the reacting particles collide with each other....
After students explore one example of an endothermic change and one example of an exothermic change, they are then asked to explore the connection between energy changes and chemical reactions. To do this, students may need some guidance to arrive at the idea that temperature changes may also accompany dissolving.
For photosynthesis to occur, plants need: · Light energy from the sun · Chlorophyll to absorb light energy · Carbon dioxide from the atmosphere and from respiration in plant cells · Water which is absorbed by the roots and transported to the leaves by the xylem tubes....
Several general types of chemical reactions can occur based on what happens when going from reactants to products. The more common types of chemical reactions are as follows:
This investigation introduces the concepts of enthalpy (heat) of ΔH in the context of exothermic and endothermic reactions. To give students a deeper grounding in the basics and reinforce basic concepts covered previously, you may wish to review the mechanics of chemical changes, how to write balanced chemical equations, and the law of conservation of energy.
In this activity, you will explore the energy changes that accompany chemical reactions. To understand the energy implications of chemical reactions, it’s important to keep in mind two key ideas:
To understand this, consider the chemical reaction between vinegar (also known as acetic acid to chemists) and baking soda (known as sodium bicarbonate). Before the atoms of acetic acid and sodium bicarbonate can be rearranged to form the products, the bonds between the atoms in those molecules must be broken, and because the atoms are attracted to one another, it takes energy to pull them apart.
Photosynthesis is the process by which phototrophs convert carbon
dioxide and water into simple carbohydrates and oxygen in the presence
of chlorophyll, using sunlight.
Photosynthesis is summarised by the
However this equation is somewhat miss leading, as photosynthesis is a
In single displacement reactions, only one chemical species is displaced. In , or , two species (normally ions) are displaced. Most of the time, reactions of this type occur in a solution, and either an insoluble solid (precipitation reactions) or water (neutralization reactions) will be formed.
In this investigation, students classify chemical reactions as exothermic or endothermic. Next, students explore the relationship between an observed change in temperature and the classification of a change as chemical or physical.
The whole process
takes place all the time during the hours of daylight, but only the
light-independent reactions of photosynthesis are sometimes referred
as the dark reactions (however this does not mean they only occur in
the dark, where as in fact they occur continuously).