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Three
States of Matter
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Scientific
Reasons
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Q8) Mercury does not wet the walls of container. |
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Wetting or non-wetting quality of a liquid depends on surface tension, cohesive and adhesive forces .Mercury has very high surface tension and possess very strong cohesive forces. On the other hand in mercury adhesive forces are very small. That’s why mercury does not wet the walls of container. |
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| Q9) A drop of ink spreads on blotting paper. | |||
| Blotting paper has a large number of pores (tiny holes) on its surface. Each pore acts like a capillary tube. When a drop of ink is placed on a blotting paper, it spreads on the paper due to capillary action. | |||
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Q10) It is easier to pour water than honey. |
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| It is due to the difference in viscosity. Honey is more viscous (thick) than water due to strong inter-molecular forces . On the other hand water is less viscous than honey. Therefore it is easier to pour water as compared to honey | |||
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Q11) Temperature of a liquid remains constant at boiling point on heating. |
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| Temperature of a liquid remains constant at boiling point despite the addition of heat. It is because of the fact that all the heat supplied at boiling point is consumed in converting liquid into vapour phase. | |||
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Q12) Why does the pressure of a gas increases when volume is decreased at constant temperature? |
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At constant temperature if volume of a gas is reduced, gas molecules will come close to each other but there is no change in the velocity of gas molecules. In small volume chances of molecular collision with the walls of container increases thus pressure of gas also increases. i.e. V µ 1/P which is according to Boyle’s law. |
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| Q13) At constant pressure increase in temperature decreases the volume of a gas. | |||
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If at constant pressure, temperature of a gas is reduced, velocity and K.E of gas molecules will also decrease . Due to decrease in K.E, force of attraction between gas molecules will become large, consequently volume of gas decreases i.e. V µ T which is according to Charle’s law. |
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