For rusting, the presence of both oxygen and moisture (water vapour) is required. In coastal areas the quantity of moisture content in air is high (highly humid) as compared to desert regions (low humid), so the rusting becomes faster in coastal areas. https://www.tiwariacademy.com/ncert-solutions/cRead more
For rusting, the presence of both oxygen and moisture (water vapour) is required. In coastal areas the quantity of moisture content in air is high (highly humid) as compared to desert regions (low humid), so the rusting becomes faster in coastal areas.
For rusting, the presence of both oxygen and water (or water vapour) is required. The coat of the paint prevents direct contact of iron with air and oxygen and thus prevents it from rusting. https://www.tiwariacademy.com/ncert-solutions/class-7/science/chapter-6/
For rusting, the presence of both oxygen and water (or water vapour) is required. The coat of the paint prevents direct contact of iron with air and oxygen and thus prevents it from rusting.
Crystals of copper sulphate are prepared as follows: • Take a water in a beaker and add a few drops of dilute sulphuric acid. • Heat the water. When it starts boiling add copper sulphate powder slowly with continuous stirring. • Continue adding copper sulphate powder till saturation level. • FilterRead more
Crystals of copper sulphate are prepared as follows:
• Take a water in a beaker and add a few drops of dilute sulphuric acid.
• Heat the water. When it starts boiling add copper sulphate powder slowly with continuous stirring.
• Continue adding copper sulphate powder till saturation level.
• Filter the solution and left for cooling.
• Leave undisturbed the solution when it is cooling.
• We can observe the crystals of copper sulphate after few hours.
Burning of wood is a chemical change because wood on burning converted to new substances like ash (carbon), carbon dioxide gas, water vapour, heat and light. The change is irreversible. While cutting of wood in smaller pieces is a physical change because the original composition of wood does not chaRead more
Burning of wood is a chemical change because wood on burning converted to new substances like ash (carbon), carbon dioxide gas, water vapour, heat and light. The change is irreversible.
While cutting of wood in smaller pieces is a physical change because the original composition of wood does not change. No new substances are formed.
Setting of curd is a chemical change since a new substance (lactic acid) is formed which differs in taste from the original substance (fats and proteins) i.e. milk. Also the change is irreversible (curd cannot be converted into milk). https://www.tiwariacademy.com/ncert-solutions/class-7/science/chaRead more
Setting of curd is a chemical change since a new substance (lactic acid) is formed which differs in taste from the original substance (fats and proteins) i.e. milk. Also the change is irreversible (curd cannot be converted into milk).
Physical Changes: On heating, candle wax gets melted is a physical change. Since it again turns into solid wax on cooling. Chemical Changes: The wax near to flame burns and gives new substances like Carbon Dioxide, Carbon soot, water vapour, heat and light. Cooking of food, is another example whereRead more
Physical Changes: On heating, candle wax gets melted is a physical change. Since it again turns into solid wax on cooling.
Chemical Changes: The wax near to flame burns and gives new substances like Carbon Dioxide, Carbon soot, water vapour, heat and light.
Cooking of food, is another example where both physical and chemical changes occurs.
This a chemical change as new products are formed. Baking soda + Lemon juice ------------> Salt + Carbon dioxide + Water When acid react with carbonates, salt is formed releasing carbon dioxide and water. https://www.tiwariacademy.com/ncert-solutions/class-7/science/chapter-6/
This a chemical change as new products are formed.
Baking soda + Lemon juice ————> Salt + Carbon dioxide + Water
When acid react with carbonates, salt is formed releasing carbon dioxide and water.
Changes in which only physical properties of a substance change are called physical changes. https://www.tiwariacademy.com/ncert-solutions/class-7/science/chapter-6/
Changes in which only physical properties of a substance change are called physical changes.
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.
(iii) Both processes A and B are chemical changes. https://www.tiwariacademy.com/ncert-solutions/class-7/science/chapter-6/
(iii) Both processes A and B are chemical changes.
https://www.tiwariacademy.com/ncert-solutions/class-7/science/chapter-6/
See lessExplain why rusting of iron objects is faster in coastal areas than in deserts.
For rusting, the presence of both oxygen and moisture (water vapour) is required. In coastal areas the quantity of moisture content in air is high (highly humid) as compared to desert regions (low humid), so the rusting becomes faster in coastal areas. https://www.tiwariacademy.com/ncert-solutions/cRead more
For rusting, the presence of both oxygen and moisture (water vapour) is required. In coastal areas the quantity of moisture content in air is high (highly humid) as compared to desert regions (low humid), so the rusting becomes faster in coastal areas.
https://www.tiwariacademy.com/ncert-solutions/class-7/science/chapter-6/
See lessExplain how painting of an iron gate prevents it from rusting.
For rusting, the presence of both oxygen and water (or water vapour) is required. The coat of the paint prevents direct contact of iron with air and oxygen and thus prevents it from rusting. https://www.tiwariacademy.com/ncert-solutions/class-7/science/chapter-6/
For rusting, the presence of both oxygen and water (or water vapour) is required. The coat of the paint prevents direct contact of iron with air and oxygen and thus prevents it from rusting.
https://www.tiwariacademy.com/ncert-solutions/class-7/science/chapter-6/
See lessDescribe how crystals of copper sulphate are prepared.
Crystals of copper sulphate are prepared as follows: • Take a water in a beaker and add a few drops of dilute sulphuric acid. • Heat the water. When it starts boiling add copper sulphate powder slowly with continuous stirring. • Continue adding copper sulphate powder till saturation level. • FilterRead more
Crystals of copper sulphate are prepared as follows:
• Take a water in a beaker and add a few drops of dilute sulphuric acid.
• Heat the water. When it starts boiling add copper sulphate powder slowly with continuous stirring.
• Continue adding copper sulphate powder till saturation level.
• Filter the solution and left for cooling.
• Leave undisturbed the solution when it is cooling.
• We can observe the crystals of copper sulphate after few hours.
https://www.tiwariacademy.com/ncert-solutions/class-7/science/chapter-6/
See lessExplain why burning of wood and cutting it into small pieces are considered as two different types of changes.
Burning of wood is a chemical change because wood on burning converted to new substances like ash (carbon), carbon dioxide gas, water vapour, heat and light. The change is irreversible. While cutting of wood in smaller pieces is a physical change because the original composition of wood does not chaRead more
Burning of wood is a chemical change because wood on burning converted to new substances like ash (carbon), carbon dioxide gas, water vapour, heat and light. The change is irreversible.
While cutting of wood in smaller pieces is a physical change because the original composition of wood does not change. No new substances are formed.
https://www.tiwariacademy.com/ncert-solutions/class-7/science/chapter-6/
See lessHow would you show that setting of curd is a chemical change?
Setting of curd is a chemical change since a new substance (lactic acid) is formed which differs in taste from the original substance (fats and proteins) i.e. milk. Also the change is irreversible (curd cannot be converted into milk). https://www.tiwariacademy.com/ncert-solutions/class-7/science/chaRead more
Setting of curd is a chemical change since a new substance (lactic acid) is formed which differs in taste from the original substance (fats and proteins) i.e. milk. Also the change is irreversible (curd cannot be converted into milk).
https://www.tiwariacademy.com/ncert-solutions/class-7/science/chapter-6/
See lessWhen a candle burns, both physical and chemical changes take place. Identify these changes. Give another example of a familiar process in which both the chemical and physical changes take place.
Physical Changes: On heating, candle wax gets melted is a physical change. Since it again turns into solid wax on cooling. Chemical Changes: The wax near to flame burns and gives new substances like Carbon Dioxide, Carbon soot, water vapour, heat and light. Cooking of food, is another example whereRead more
Physical Changes: On heating, candle wax gets melted is a physical change. Since it again turns into solid wax on cooling.
Chemical Changes: The wax near to flame burns and gives new substances like Carbon Dioxide, Carbon soot, water vapour, heat and light.
Cooking of food, is another example where both physical and chemical changes occurs.
https://www.tiwariacademy.com/ncert-solutions/class-7/science/chapter-6/
See lessWhen baking soda is mixed with lemon juice, bubbles are formed with the evolution of a gas. What type of change is it? Explain.
This a chemical change as new products are formed. Baking soda + Lemon juice ------------> Salt + Carbon dioxide + Water When acid react with carbonates, salt is formed releasing carbon dioxide and water. https://www.tiwariacademy.com/ncert-solutions/class-7/science/chapter-6/
This a chemical change as new products are formed.
Baking soda + Lemon juice ————> Salt + Carbon dioxide + Water
When acid react with carbonates, salt is formed releasing carbon dioxide and water.
https://www.tiwariacademy.com/ncert-solutions/class-7/science/chapter-6/
See lessFill in the blanks: Changes in which new substances are formed are called _________ changes.
Changes in which new substances are formed are called chemical changes. https://www.tiwariacademy.com/ncert-solutions/class-7/science/chapter-6/
Changes in which new substances are formed are called chemical changes.
https://www.tiwariacademy.com/ncert-solutions/class-7/science/chapter-6/
See lessFill in the blanks: Changes in which only _________ properties of a substance change are called physical changes.
Changes in which only physical properties of a substance change are called physical changes. https://www.tiwariacademy.com/ncert-solutions/class-7/science/chapter-6/
Changes in which only physical properties of a substance change are called physical changes.
https://www.tiwariacademy.com/ncert-solutions/class-7/science/chapter-6/
See less