Scalars, Vectors, Endothermic & Exothermic Reactions Explained

Scalars and Vectors

What is a scalar? A scalar is a quantity that is fully described by a magnitude only. It is described by just a single number. Some examples of scalar quantities include speed, volume, mass, temperature, power, energy, and time.

What is a vector? A vector is a quantity that has both a magnitude and a direction. Vector quantities are important in the study of motion. Some examples of vector quantities include force, velocity, acceleration, displacement, and momentum.

Endothermic and Exothermic Reactions

An endothermic reaction takes place when energy is absorbed from the surroundings in the form of heat. An exothermic reaction is when energy is released from the system into the surroundings.

Endothermic reactions must be supplied with heat and are basically the opposite of exothermic reactions. An everyday example is the cooking of an egg. Heat must be added or absorbed from the environment to cook the egg or any other food item. The two reactions differ because the amount of energy of the reactants is less than that of the products, as opposed to an exothermic reaction.

How Endothermic Reactions Affect Temperature

Endothermic reactions will cool their surroundings because the reactions draw heat energy into themselves. As heat leaves an area, the temperature will drop. If a person's hand is cold to the touch, it may be related to their skin having a lower temperature; however, heat is actually leaving the warmer body and being absorbed into the cooler hand.

Energy Storage in Chemical Reactions

Endothermic reactions also contain more energy by drawing in and storing energy in the form of chemical bonds. A product contains more net energy than the reactants did in an endothermic reaction at the beginning of the process. This is because of the stored energy. The warm hand in the previous example had energy stored in it. Exothermic reactions, on the other hand, make the surrounding environment hotter since heat energy is released, radiating energy while it progresses. A campfire is an excellent example of this reaction. The energy from the chemical bonds of paper and wood is released in the form of light and, of course, heat. Those sitting around the campfire become warm as a result of the released heat. Exothermic reactions will contain less energy because it is removed from the chemical bonds in the reactants. Activation energy, like the match for the campfire, is needed to get the process started. Following the process, the product will have lower heat and is more compact.

Examples of Endothermic and Exothermic Reactions

• Endothermic:
  • Photosynthesis (plants absorb energy from the environment)
  • Evaporation (sweating cools a person down)
• Exothermic:
  • Rain (condensation of water vapor into rain expels heat)
  • Concrete formation (water added to concrete releases heat)

In summary, endothermic reactions consist of energy or heat being absorbed from their surroundings, and exothermic reactions involve energy or heat being released into the environment. There are many examples of endothermic and exothermic reactions taking place every day.

Law of Conservation of Energy

Energy cannot be created or destroyed.