Class 7 Science - KERALA
Changes Around Us: Physical and Chemical
The Class 7 Kerala SCERT Science chapter 'Changes Around Us: Physical and Chemical' explores the different types of changes we observe in our daily lives, such as melting ice, rusting iron, and burning paper. Students will learn to distinguish between reversible and irreversible changes, as well as temporary physical changes and permanent chemical changes where new substances are formed. This chapter is fundamental for building a strong foundation in chemistry, helping students understand the behavior of matter. It holds high weightage in school examinations, frequently featuring in direct definition-based questions, identification of change types, and practical reasoning tasks.
Start Learning FreeKey Concepts
Physical Change
A temporary change in which no new substance is formed and the chemical composition of the matter remains the same.
Chemical Change
A permanent change in which one or more new substances with entirely different properties are formed.
Reversible Change
A change that can be undone to get back the original substance, such as melting of ice or freezing of water.
Irreversible Change
A change that cannot be reversed to get back the original substance, such as burning paper or cooking food.
Rusting of Iron
A chemical change where iron reacts with oxygen and moisture in the air to form a reddish-brown coating called rust.
Important Formulas
Board Exam Info
This chapter typically carries around 6 to 8 marks in the Kerala SCERT Class 7 Science examinations. Common question types include classifying given daily life changes into physical or chemical changes, explaining the conditions required for rusting, and differentiating between reversible and irreversible changes with examples.
Frequently Asked Questions
Is melting of wax a physical or chemical change?
Melting of wax is generally considered a physical change because solid wax melts into liquid wax and can solidify back on cooling, though burning of the wick is a chemical change.
Why is ripening of fruit considered a chemical change?
Ripening of fruit is a chemical change because new substances are formed, changing the color, taste, and chemical composition permanently, and the ripe fruit cannot be turned back into a raw fruit.
How can we prevent iron from rusting?
Iron can be prevented from rusting by applying a layer of paint, grease, or by applying a coating of a more reactive metal like zinc, a process known as galvanization.
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