CBSE Class 6 Science Revision Notes Chapter 6

CBSE Class 6 Science Chapter 6 Revision Notes – Changes Around Us

The various changes that take place in our environment are explained in Class 6 Science Chapter 6 “Changes Around Us.” It explains transformational processes, such as evaporation, boiling, freezing, and condensation.

Extramarks Revision Notes for Class 6 Science Chapter 6 contain all of the necessary information in a concise and well-structured format. These notes are written in simple language so that students can understand the concepts easily and quickly. It is a great tool for revising key points before examinations to score better marks. 

Revision Notes for CBSE Class 6 Science Chapter 6

Access Class 6 Science Chapter 6 Notes – Changes Around Us

What is Change?

A change is any modification to a substance’s original shape, size, or state.

Changes can be reversible and irreversible.

• Reversible Change: A change that is reversible and can be undone.

For example, melting ice and inflating a balloon.

• Irreversible Change: When something cannot be changed back to its original state, it has undergone an irreversible change.

For example, cooked  food and burnt  paper.

Two Types of Changes

• Physical Change: A change in a substance’s physical characteristics, such as its form, size, volume, colour, appearance, or state (solid, liquid, or gas), is referred to as physical change. Most physical changes are reversible changes.

For example, melting an ice cube, freezing water, mixing sand and water, and boiling water.

• Chemical Change: A chemical change is defined as the transformation of one chemical substance into one or more distinct substances. Chemical changes mostly include irreversible changes.

For example, burning of wood, soured milk, mixing acid and base, and rusting of iron. 

 Some Factors Leading to Change

• Evaporation: Evaporation is the physical process by which a liquid transforms into a gaseous state. It typically occurs on the surface of liquids.
• Melting: Melting is the physical transformation of a solid into a liquid. A solid melts when heat is applied to it.
• Freezing: When a liquid’s temperature is lowered, it undergoes a transformation into a solid. Heat is transferred from the body to its surroundings.

• Boiling: Boiling is the rapid vaporisation of a liquid. It usually happens when a liquid is heated to a temperature where its vapour pressure is higher than that of the environment, such as the air pressure.

• Condensation: Condensation is a physical change where the gas changes to a liquid. Any gas can condense at high pressure and low temperature.
• Expansion: When the temperature rises, a substance’s particle expands or loosens. When this occurs, the substance expands.
• Contraction: When the temperature drops, the particles of the substance contract or tighten. When this occurs, the material is said to contract or decrease in size.
• Applying Pressure: Applying pressure to an object can alter its size. It also compresses and liquefies air.

Some Examples of Changes Around Us

• The weather changes every season, and seasons change every year.

• Crops and trees grow with time to bear fruits and grains. It is an irreversible change.

•  Blooming of flowers is an irreversible change. Flowers cannot be transformed back into buds.
• Paper burning is an irreversible change. After burning paper, a new substance called ash is formed. The appearance and properties of this new substance differ from those of paper.

• The moon waxes and wanes every month.

• Fruit ripening is an irreversible process because it is impossible to separate raw fruits from ripened or mature ones.

• Our bodies  are changing, including the rate at which our hair, nails, and height increase over time. These changes are irreversible. 

• Corrosion/rusting of iron is an example of chemical change. Rust develops on iron when it is exposed to air and moisture. Rust is simply Iron Oxide, a byproduct of the process. The iron’s surface colour also varies over time.