Five examples of Physical and Chemical changes (chemistry project)

 Introduction 

Everything around us undergoes certain changes. Changes can be either physical or chemical. 

Physical change is a type of change where the physical properties of matter change. A change of state of matter, change in colour, odour, solubility, etc. all are examples of physical change.

A chemical change is a type of change where the chemical properties of matter change. It is commonly called a chemical reaction.

1) Physical Change:

i) Crushing a Can: 

When you crush an aluminum can, it undergoes a physical change as its shape is altered without any change in its chemical composition. The aluminum remains aluminum, but its form is now flattened.

ii) Stretching a Rubber Band:

 Stretching a rubber band causes a physical change as its length and shape are altered. However, the chemical composition of the rubber remains the same. When released, the rubber band returns to its original shape due to its elastic properties.

iii)Crumpling Paper: 

Crumpling a piece of paper involves a physical change because it alters the shape and texture of the paper without changing its chemical composition. The paper remains paper, but its appearance is modified.

iv)Tearing Paper

When you tear a paper, it is also a physical change. The shape and size of paper changes but its chemical composition remains same. It is reversible process as we can make the paper again from these pieces.

v)Freezing of Water

When we freeze water in the refrigerator, it turns into ice. Ice is not a new material, but water. When we take ice out of the refrigerator, it melts by absorbing heat from the environment and again converting into liquid form.

2) Chemical Change:

i) Digestion

Thousands of chemical reactions take place during digestion. Enzyme amylase present in saliva breaks down sugars and carbohydrates present in food to form simpler forms which the body can absorb. Hydrochloric acid in the stomach reacts with food to further break it down. So during digestion, proteins break into amino acids, fats break into fatty acids and glycerol and carbohydrates break into simple sugars.

ii) Detergent and Soap Reactions

A chemical reaction happens when we use soap and water to clean our hands. Water by itself does not clean our hands, and it reacts with any detergent or soap. Emulsification is the chemical reaction that is used to eliminate dirt from our hands. During the process, surface tension is reduced. Because detergents include enzymes, dishwashing requires several reactions. These enzymes assist us by eliminating dirt from garments.

iii) Ripe and rotten bananas

Various bananas are on the kitchen counter, sometimes they are green when purchased but eventually start to turn yellow and eventually ripen to the point of rotting, the chemical composition of bananas has changed over time resulting in new molecules.

iv) Burning of Wood: 

When wood burns, it undergoes a chemical change known as combustion. The heat breaks down the complex organic molecules in wood into simpler compounds such as carbon dioxide, water vapor, and ash, releasing energy in the form of heat and light.

v) Souring of Milk: 

When milk sours, it undergoes a chemical change due to the action of bacteria on the lactose sugar present in the milk. The bacteria ferment the lactose, producing lactic acid, which causes the milk to curdle and develop a sour taste.

Conclusion

This project on changes in chemistry has deepened our understanding of how substances transform, both physically and chemically. By exploring factors like temperature and concentration, we've uncovered insights with practical applications in various fields. This research underscores the importance of continued exploration in chemistry and its relevance to real-world challenges.