Changes are a natural aspect of life and are constantly present. Sometimes just one substance is involved. Whereas other times two or more than two substances are involved. Everything is an illustration of change, from dissolving salt in the water to churning of milk.
A change in the condition or state of the material occurs during some of the changes. While in others, the substance's current bonds break, leading to the formation of new bonds. It leads to the formation of new substances. There are two types of changes:
PHYSICAL CHANGE CHEMICAL CHANGE Physical changes are temporary and reversible. Chemical changes are permanent and irreversible. In a physical change, only the physical properties of a substance are affected. The composition, physical and chemical properties change during a chemical change. No new substance is formed. One or more new substances are formed. In a physical change, the composition remains the same, but the molecules of the matter undergo rearrangement. In a chemical change, the molecular composition changes. A little or no energy is absorbed or released. Production and absorption of energy take place. In a chemical reaction, the primary form of energy involved is thermal energy.
A chemical change leaves behind indicators to suggest that a chemical reaction might be underway. These indicators can be
A chemical reaction in which the energy is absorbed is known as an endothermic process. A chemical reaction where the energy is released is known as an exothermic process.
Chemical changes are greatly studied using thermodynamic systems, whereas physical changes can be studied by mere observation.
Put some ice cubes in a jar and set them aside. Place the container in a warm area. After a few minutes, the ice melts and gets converted to water. Place this container of water in the freezer once more. The ice is formed after one hour. This change that involves only a change in the state of matter is called a physical change.
Use magnesium in the form of a thin strip or ribbon. Using sandpaper, clean the tip of the strip or ribbon. Place the strip or the ribbon on the flame of a burning candle. It emits a bright white light when lit. When entirely burned, it leaves fine ash behind. This change that caused the emission of bright light and residues, is because of the formation of a new product, hence the change is called a chemical change.
The change that occurred is: Magnesium (Mg) + Oxygen (O2 ) → Magnesium oxide (MgO)