Explanation
Thermostate is used in electric apparatus like refrigerator, iron etc for automatic cut off. Therefore for metallic strips to bend on heating their coefficient of linear expansion should be different.
Substances are classified into two categories
(i) Water like substances which expand on solidification,
(ii) CO2 like (Wax, Ghee etc.) substances which contract on solidification.
Their behaviour regarding solidification is opposite. Melting point of ice decreases with rise of pressure but that of wax etc increases with increase in pressure. Similarly ice starts forming from top to downwards whereas wax starts its formation from bottom to upwards.
Initially, on heating temperature rises from —10°C to 0°C . Then, ice melts and temperature does not rise. After the whole ice has melted, temperature begins to rise until it reaches 100°C. Then, it becomes constant, as at the boiling point will not rise.
The volume of matter in portion AB of the curve is almost constant and pressure is decreasing. These are the characteristics of liquid state.
In the given graph, CD represents liquid state.
Density of water is maximum at 4°C and is less on either side of this temperature.
The horizontal parts of the curve, where the system absorbs heat at constant temperature must depict changes of state. Here, the latent heats are proportional to lengths of the horizontal parts. In the sloping parts, specific heat capacity is inversely proportional to the slopes.
Anomalous density of water is given by (a). It has maximum density at 4°C, when ice is formed it floats.
With rise in pressure, melting point of ice decreases. Also, ice contracts on melting.
Celsius scale was the first temperature scale and Fahrenheit is the smallest unit measuring temperature.
Melting is associated with increasing of internal energy without change in temperature. In view of the reason being correct the amount of heat absorbed or given out during change of state is expressed Q = mL , where m is the mass of the substance and L is the latent heat of the substance.
The temperature of land rises rapidly as compared to sea because of specific heat of land is five times less than that of sea water. Thus, the air above the land becomes hot and light so rises up so pressure drops over land. To compensate the drop of pressure, the cooler air from sea starts blowing towards land, setting up sea breeze. During night, land as well as sea radiate heat energy. The temperature of land falls more rapidly as compared to sea water, as sea water consists of higher specific heat capacity. ‘[he air above sea water being warm and light rises up and to take its place the cold air from land starts blowing towards sea and set up breeze
The potential energy of water molecules is more. The heat given to melt the ice at 0°C is used up in increasing the potential energy of water molecules formed at 0°C.
Water evaporates quickly because of lack of atmospheric pressure, also temperature of moon is much higher during day time but it is very low at night.
Specific heat of a body is the amount of heat required to raise the temperature of unit mass of the body through unit degree. When mass of a body is less than unity, then its thermal capacity is less than its specific heat and vice-versa.
Water has maximum density at 4°C. On heating above 4°C or cooling below 4°C, density of water decreases and its volume increases. Therefore, water overflows in both the cases.
Please disable the adBlock and continue. Thank you.
