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Practice each question, then open the answer or worked solution.
The gas we use in the kitchen is called liquified petroleum gas (LPG). In the cylinder, it exists as a liquid. When it comes out from the cylinder, it becomes a gas (Change – A) then it burns (Change – B). The following statements pertain to these changes. Choose the correct one.
The answer is (ii) Process – B is a chemical change.
Anaerobic bacteria digest animal waste and produce biogas (Change – A). The biogas is then burnt as fuel (Change – B). The following statements pertain to these changes. Choose the correct one.
The answer is (iii) Both processes A and B are chemical changes.
Class 7 Science NCERT Solutions for Chapter 6 – Physical and Chemical ChangesWe all see different types of changes in our daily life activities, among which a few are reversible, and a few are irreversible. Some examples of these changes include the melting of ice, a bud changing to a flower, the melting of candle wax and a lot more. Based on their changes, they are classified into physical change and chemical change.
Physical change: A change that changes only the physical traits of the substance without making any change in its internal structure. Examples of physical change include boiling water, chopping wood, dissolving sugar in water, crumpling of paper, melting an ice cube, etc.
Chemical change: A change that changes by affecting the internal structure of the substance to form a new substance. Examples of chemical change include digesting food, burning wood, baking a cake, curdling milk, mixing acid, boiling an egg, rusting of iron, etc.
Students can learn more in detail about these topics by referring to the