Learn from School Connect Online in this chapter we will learn the things,like turning day into night, night into a day, rising and setting of sun and moon, changing of climate, melting of ice, and lot more. Some changes are quick and some takes time lets study more in this chapter

CBSE Class 6 Science Notes Chapter 6 Changes Around Us

The different topics covered in CBSE Class 6 Science Chapter 6 are tabulated below:

Ex. 6.1 – Can All Changes Always Be Reversed?

Changes caused by heating: When an object is heated, it gets affected in one or many possible ways.

• Some objects get hot but do not change in any other way.
• Some objects get hot and also expand in size.
• Some objects get hot and begin to bum.
• Some objects get hot and change their state.

Changes by applying pressure: When we apply force to an object:

• We can change its shape and size.
• Air can be compressed.
• Metals can be hammered into thin sheets.
• Elastic can be stretched.
• Cotton can be spun into thin threads.

Chemical changes: These are the changes in which chemical properties of a substance change, and a new substance is formed. For example, cooking food.

Characteristics of chemical changes:

• Properties of products are different from the properties of reactants.
• Most of the chemical changes are irreversible.
• These changes always result in energy changes.

Physical changes: These are the changes in which only physical property of a substance changes and no new substance is formed.Characteristics of physical changes:

• No new substances are formed.
• Products are identical to the reactants.
• These changes are reversible.

Reversible changes: These are the changes that can be reversed.

For example : stretching of rubber

Irreversible changes: These are the changes which cannot be brought back to its original state.

For example : burning paper

Ex. 6.2 – Could There Be Other Ways To Bring A Change?

Melting: A process in which a solid melts to become a liquid on heating is called melting.

Melting point: A constant temperature at which a solid starts melting. This temperature is called the melting point of that solid.

Freezing: A process in which liquid changes into solid form is called freezing.

Changes: Many changes are taking place around us on their own, e.g., flowers bloom and then wither away. We can also bring a change, e.g., change in the size of a balloon by blowing air in it.

Natural changes: The changes which occur in nature on their own are called natural changes. For example, change of day and night, change of season.

Slow changes: The changes which take longer time to occur are called slow changes. For example, rusting of iron, tooth decay.

Contraction: A process in which an object becomes smaller or shrinks is called contraction.

Evaporation: A process in which liquid changes into vapour is called evaporation.

Expansion: A process in which an object becomes bigger in size, e.g. metals expand on heating.

Separation : The separation of the components of a mixture or an impure substance are carried out with the following purposes :

a. To remove the unuseful or harmful component.

b. To obtain the useful component.

c. To remove impurities for getting a pure sample.

Conclusion :

• Changes happen around us and also within us.
• Some changes are reversible, while some others are irreversible.
• Some changes are physical changes; some are chemical changes.
• Heating causes expansion in a material.
• Cooling causes contraction in a material.
• Gases expand the most and solids expand the least.
• Gases contract the most and solids contract the least.

CBSE Notes for Class 6 Science Free Download for All Chapters

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