Review on chemical reactions for Grade :7

A chemical reaction is defined as the process, wherein a set of chemical substances react with each other, which leads to their conversion into other different forms. The initial substances used the reaction are collectively called reactants, while the final substances formed after the reaction are known a products. In general, the chemical properties of the reactants and products are different from each other.

Aerobic Respiration
Do you know indulging in physical movements is associated with a chemical reaction? The process requires energy, which is yielded by aerobic respiration. Over here, respiration helps breaks down glucose (an energy source) into water, carbon dioxide and energy in form of ATP (adenosine triphosphate). The balancedcellular respiration equation is represented as:

C₆H₁₂O₆ + 6O₂ → 6CO₂+ 6H₂O + Energy

Photosynthesis
Photosynthesis is the process by which green plants manufacture their own food. This occurs in presence of sunlight and other raw materials, namely carbon dioxide and water. The chlorophyll pigment harvests the light energy from sunlight, which is then converted into glucose by the phenomenon of photosynthesis. In short, it is the opposite of aerobic respiration. Theequation for photosynthesis is:

6 CO₂+ 6 H₂O + Light energy → C₆H₁₂O₆ + 6 O

<sub>Propane Grill
Have you ever prepared meat in a propane grill? The meat placed over the burner is cooked with the help of heat energy released after burning of propane gas. Thus, propane is the reactant which when burnt with the help of oxygen gives heat energy and other byproducts. Check out the balanced equation for the combustion reaction that take place in a propane grill::

C3H8 + 5O2 → 4H2O + 3CO2 + energy</sub>

Look at the cases below indicate whether there is a chemical reaction taking place .

a-water is freezed ,melted ,then evaporated .

b-dissolve sugar in water.