Melting of wax is a change where a solid changes to liquid state. Give one more such change which you observe in your surroundings.
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Name one metal and one non-metal that exist in liquid state at room temperature. Also name two metals having melting point less than 310K
Metal: Mercury (Hg); Non-metal: Bromine (Br) Two metals with melting points less than 310K are Cesium (Cs) and Gallium (Ga).
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While lighting a candle, Paheli observed the following changes (i) Wax was melting.
(i) Wax was melting. (iv) Melted wax was getting solidified.
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If you happen to go to a desert, what changes do you expect to observe in the urine you excrete? You would
(i) excrete small amount of urine. (iii) excrete concentrated urine.
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Solid A is a very hard electrical insulator in solid as well as in molten state and melts at extremely high temperature. What type of solid is it?
It is a covalent solid such as SiO2, diamond, SiC, AlN, etc. Covalent solids (except graphite) have very high melting point and are insulators.
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A solid floats in a liquid in a partially dipped position. (a) The solid exerts a force equal to its weight on the liquid.
(a) The solid exerts a force equal to its weight on the liquid. (b) The liquid exerts a force of buoyancy on the solid which is equal to the weight of...
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A solid is completely immersed in a liquid. The force exerted by the liquid on the solid will
(c) decrease if it is taken partially out of the liquid (d) be in the vertically upward direction. EXPLANATION: The force exerted by the liquid on the solid is equal to the volume...
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A liquid can easily change its shape but a solid can not because (a) the density of a liquid is smaller than that of a solid
(b) the forces between the molecules is stronger in solid than in liquids EXPLANATION: The shape will change only if the molecules have some freedom of movement. In a solid the forces...
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A solid is completely immersed in a liquid. The force exerted by the liquid on the solid will (a) increase if it is pushed deeper inside the liquid
(c) decrease if it is taken partially out of the liquid (d) be in the vertically upward direction. EXPLANATION: The force exerted by the liquid on the solid is equal to the volume...
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State why heat changes in physical and chemical processes are indicated by enthalpy changes and not by entropy changes?
Most of the processes are carried out in an open system i.e, at constant pressure.
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Predict the entropy change in- (i) A liquid crystallizes into solid (ii) Temperature of a crystalline solid raised from 0K to 115K
(i) Entropy decreases because molecules attain an ordered state. (ii) Entropy increases because from 0K to 115K average kinetic of molecules increases.
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