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Three identically shaped deflated balloons are attached to the mouth of three empty glass tubes, I, II and III. Each test tube is placed inside a glass tumbler containing water. All the three glass tumblers contain the same amount of water that has been heated to attain different temperatures of T1, T2 and T3 respectively. The temperature is the highest in test tube II and the lowest in test tube III. The temperature in test tube I is in between II and III. After some time, changes were observed in the volume of air inside the balloons. It is observed that the volume of air inside the balloon attached to test tube

When the test tubes attached with deflated balloons are placed in different glass tumblers containing water heated to different temperatures, the... View Article

Explain the following. (a) Why is the tungsten used almost exclusively for filament of electric lamps? (b) Why are the conductors of electric heating devices, such as bread-toasters and electric irons, made of an alloy rather than a pure metal? (c) Why is the series arrangement not used for domestic circuits? (d) How does the resistance of a wire vary with its area of cross-section? (e) Why are copper and aluminum wires usually employed for electricity transmission?

(a) Tungsten is used as filament in electric bulbs The melting point and resistivity of Tungsten are very high. At high temperatures, it does... View Article

While teaching the topic of physical and chemical changes, Mahima’s teacher listed the conditions that take place during a change. a) Change in state b)Change in colour c) Evolution of a gas d)Change in temperature He then asked Mahima to identify the conditions based on which it can be said with certainty that a particular change is chemical in nature. Among the changes that are listed by the teacher, which changes should be selected by Mahima?

Any change that is accompanied by evolution of gas is known as a chemical change. Therefore, whenever a gas is evolved in a process, it can be... View Article

Calculate the amount of ice which is required to cool 150 g of water contained in a vessel of mass 100 g at 30°C, such that the final temperature of the mixture is 5°C. Take specific heat capacity of material of vessel as 0.4 J g1°C-1 ; specific latent heat of fusion of ice = 336 J g-1; specific heat capacity of water = 4.2 J g-1°C-1.

Heat lost by the vessel and water= [150 x 4.2 x (30 - 5) J + 100 x 0.4 x (30-5)] J = (150 x 4.2 x 25 + 100 x 0.4 x 25) J = (15,750 + 1000) J=... View Article

Smita studied about the Modern Periodic Table. She placed hydrogen, lithium, sodium, and calcium in the same group in the periodic table. However, her teacher told her that she has placed one element incorrectly in the periodic table.(Atomic numbers of H, Li, Na, and Ca are 1, 3, 11, and 20 respectively) Which element has been placed incorrectly by Smita?

Elements containing same number of valence electrons are present in the same group of the modern periodic table. The number of valence electrons... View Article