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.
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 less