Class 7 Science - WEST-BENGAL
Changes Around Us: Physical and Chemical
In the West Bengal Board (WBBSE) Class 7 Science chapter 'Changes Around Us: Physical and Chemical', students explore the two primary types of transformations occurring in daily life. A physical change alters the physical properties like shape, size, or state without creating a new substance, such as melting ice or dissolving sugar in water. Conversely, a chemical change results in the formation of entirely new substances with different chemical properties, like rusting of iron or burning paper. Understanding these changes is crucial for WBBSE board exams as it forms the foundational building block for advanced chemistry in higher classes.
Start Learning FreeKey Concepts
Physical Change
A temporary change in which no new substance is formed and the chemical composition remains the same.
Chemical Change
A permanent change where one or more new substances with different properties are formed.
Rusting of Iron
A chemical reaction where iron reacts with oxygen and moisture in the air to form a brown flaky layer called rust.
Crystallization
A physical process used to obtain pure crystals of a substance from its solution, such as getting salt from seawater.
Galvanization
A method of protecting iron from rusting by coating it with a thin layer of zinc.
Important Formulas
Board Exam Info
In the West Bengal Board (WBBSE) Class 7 final examinations, this chapter typically carries around 5 to 8 marks. Common question types include short answer questions, differentiation between physical and chemical changes, reasoning questions (e.g., 'Why is burning of paper a chemical change?'), and diagram-based or practical application questions like rusting prevention.
Frequently Asked Questions
Is melting of ice a physical or chemical change?
Melting of ice is a physical change because water only changes its state from solid to liquid, and no new substance is formed.
Why does ripening of fruit considered a chemical change?
Ripening of fruit is a chemical change because the fruit changes its color, taste, and texture permanently, and new chemical substances are formed.
Can a chemical change be reversed?
Most chemical changes are permanent and cannot be easily reversed, unlike physical changes which are mostly reversible.
Learn Changes Around Us: Physical and Chemical with Your AI Tutor
10 different ways to study this chapter. Free for 3 chapters per day.
Lecture
Key Points
Interactive
Quiz
Flashcards