Topic 7: Causes of Change
How does energy affect change?
The heat generated in the chemical reaction transmits for it and diffuses air. The heat causes physical phenomena, such as movement of air, and expansion of an adjoining substance.
Melting point is the temperature where water melts. Boiling point is when water boils. Freezing point is when water freezes. Heat causes the three, and melting, boiling, and freezing are reversible changes, since the temperature ca be adjusted so that water can melt/boil/freeze/etc. The difference of heat and temperature is that temperature is a measure of the average kinetic energy of random motions of particles in a substance, and the heat is the measure of the total amount of energy transfered from a high temperature object to a low temperature one.
How do enthalpy and entropy drive and affect changes?
When a substance dissolves or it evaporates, volume expands, density becomes small and becomes light relatively. The substance which became light will obtain impelling force, go up, and have free energy. However, since it is gradually spreading due to the law of entropy, the energy is also becoming small and will stood still. Examples of high entropy is melted ice, a broken pitcher, etc. Entropy is a disorder of a system so the higher the entropy, the higher the randomness or disorder of system. Enthalpy is the total energy content of a system, and enthalpy change is the heat energy released or absorbed when a physical or chemical change occurs at constant pressure.
What are your energy needs?
In order for man to make a living, the energy of life activities is needed. Therefore, this which takes in a calorie, is assimilated and takes out energy by decomposing it in a body, known as consumption of energy.
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