A topic from the subject of Calibration in Chemistry.
Chemical reactions are fundamental to understanding the molecular world and play a crucial role in various scientific fields and industrial processes. By studying chemical reactions and energy, we can gain insights into the nature of matter and utilize chemical transformations to create new materials, improve existing technologies, and address societal challenges.
Chemical reactions are processes that involve the rearrangement of atoms and molecules. They can be classified as either exothermic or endothermic, depending on whether they release or absorb energy.
Exothermic reactions release energy to the surroundings, often in the form of heat, light, or sound. The products have lower energy than the reactants. Examples of exothermic reactions include combustion (e.g., burning wood, propane gas), the neutralization of an acid and a base, and many oxidation reactions (e.g., rusting).
Endothermic reactions absorb energy from their surroundings. The products have higher energy than the reactants. The energy is often supplied as heat, but it could also be supplied as light or electricity. Examples of endothermic reactions include photosynthesis, the decomposition of calcium carbonate, and the melting of ice.
The energy change in a chemical reaction is called the enthalpy change (ΔH). A negative ΔH indicates an exothermic reaction (energy released), while a positive ΔH indicates an endothermic reaction (energy absorbed). Enthalpy change is a measure of the difference in heat content between the products and the reactants of a reaction.
Activation Energy: All chemical reactions, whether exothermic or endothermic, require an initial input of energy known as activation energy (Ea). This energy is needed to break the bonds in the reactants and initiate the reaction. Once the reaction starts, an exothermic reaction releases more energy than it requires, while an endothermic reaction absorbs more energy than it releases.
Key points:
Chemical reactions involve the breaking and forming of chemical bonds, resulting in a change in the arrangement of atoms. These changes are often accompanied by energy transfer in the form of heat, light, or other forms of energy. Reactions that release energy are called exothermic reactions, while those that absorb energy are called endothermic reactions.
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Observations: The temperature increase indicates that energy is released during the dissolution of NaOH in water. This is an exothermic reaction.
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Observations: The temperature decrease indicates that energy is absorbed during the dissolution of NH₄NO₃ in water. This is an endothermic reaction.
Safety Precautions: Always wear appropriate safety goggles when performing these experiments. Sodium hydroxide is corrosive; handle it with care and avoid skin contact. Dispose of the chemical waste properly according to your school's or institution's guidelines.