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Decomposition and energy change
A topic from the subject of Decomposition in Chemistry.
Decomposition and Energy Change in Chemistry
- Decomposition reactions: Chemical reactions in which a single compound breaks down into two or more simpler compounds.
- Energy change: Decomposition reactions can be either endothermic (absorb energy) or exothermic (release energy).
- Endothermic decomposition: Requires energy input to overcome the activation energy barrier and break the bonds of the reactant molecule.
- Exothermic decomposition: Releases energy as the bonds of the reactant molecule are broken and the products are formed.
- Activation energy: Minimum amount of energy that must be supplied to initiate a chemical reaction.
- Factors affecting decomposition reactions: Temperature, pressure, catalysts, and the nature of the reactant.
- Applications of decomposition reactions: Production of fuels, explosives, and ceramics; waste treatment; and food preservation.
Decomposition and Energy Change Experiment
Objective: To investigate the release or absorption of energy during chemical decomposition reactions.
Materials:
- Potassium chlorate (KClO3)
- Test tube
- Bunsen burner
- Splint
- Magnesium ribbon
- Glass beaker
Procedure:
- Place a small amount of potassium chlorate into a test tube.
- Insert a burning splint into the test tube.
- Heat the test tube gently over a Bunsen burner.
- Observe the reaction and record any changes.
- Clean the test tube and repeat the experiment, this time with a piece of magnesium ribbon.
Observations:
- In the potassium chlorate experiment, the reaction is exothermic, releasing a large amount of heat and light. The splint glows brightly, and a popping sound may be heard.
- In the magnesium ribbon experiment, the reaction is endothermic, absorbing energy from the surroundings. The magnesium ribbon burns with a bright white flame, and the test tube feels cool to the touch.
Significance:
This experiment demonstrates the concept of energy change in chemical reactions. Exothermic reactions release energy, while endothermic reactions absorb energy. This energy change can be measured and used to predict the reactivity of different substances. Understanding energy change is crucial in fields such as thermodynamics and chemical engineering.