B. Very Short Answer Type Questions
1. What conditions are required for change of iron to rust?
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2 Is a physical change reversible or irreversible change?
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3. What do you understand by physical properties of a substance?
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4. Name four characteristics which are included in the physical properties of matter.
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5. What are the two important conditions for rusting?
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6. What happens when magnesium oxide is dissolved in water?
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Class 7
Answers
Answer:
1) oxygen and water vapour
2) physical change are reversible change
3) the physical properties of a substance means the appearance, texture, colour, odor etc of a substance
4) colour, texture, solubility, density
5) the presence of air(Oxygen) and water vapour are two conditions for rusting of iron
6) when magnesium oxide us dissolved in water then it forms magnesium hydroxide
Answer:
ans 1. keep the iron in that place where the air is moist.
ans 2. reversible.
ans3. Physical properties can be observed or measured without changing the composition of matter.
ans4.1. melting point
2. boiling point.
3. electrical conductivity.
4. solubility.
ans5. 1.presence of moisture in air.
2.presence of water vapor in air.
ans6. Magnesium hydroxide forms in the presence of water (MgO + H2O → Mg(OH)2), but it can be reversed by heating it to remove moisture.