  Patterns of problems

## Thermal Properties Of Matter

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1
Patterns: Calorimetry
Discription: Principle of calorimetry is "Heat loss = Heat gain". Questions on this pattern is based on Mixing of two or more fluid at different temperature or ice/ water is in contact with steam. A Container in which this process is taking place is called calorimeter. During the process temperature of calorimeter can also changes, so to calculate amount of heat gain or loss by a calorimeter we use water equivalent. A key point for this pattern is, finally all substance along with the calorimeter coexist in thermal equilibrium.
Question may ask: to calculate mixture equilibrium temperature, Amount of ice/water remains in mixture at equilibrium condition, Specific heat capacity of unknown liquid, Water equivalent of calorimeter.
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2
Patterns: Linear expansion in solid
Discription: Temperature changes the atomic distance in substance due to which its size also goes changes. Change in linear dimension of object is written as . Time period of pendulum clock depends on the size of pendulum, if its length changes its time period goes affected (Loss or gain in time ). Similar thing happens with scale measurement, it shows correct measurement at a particular temperature but if you try to measure at a different temperature, error in its measurement can be noticed. In such scenario True reading . Temperature also develops street in the rod if we do not provide enough space to expand. If, in a free situation length of rod could change by but it has only length to expand then thermal stress will develop due to insufficient length for free expansion .
In case of bimetallic strips, due to presence of two different materials having different coefficient of linear expansion, different amount of elongation takes place that makes strip circular arc and radius of arc of strip is . But in case of rods with its ends welded together, does not bend and get same elongation. Ends of one rod pull/push other rod ends and attend equilibrium.
Question may ask: Change in dimension of rod, Loss and gain in time of pendulum clock, Error in scale reading, Thermal street in rigidly fixed rod, Radius of bi-metallic strip, Change in length of composite rods with its ends have no relative movement.
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3
Patterns: Volume expension in solid
Discription: Volume expansion can be seen in Solid, liquid and gas. for solid, coefficient of volume expansion is three times of coefficient of linear expansion. And change in volume is written as . If we try to raise the temperature of fluid, temperature of fluid and container increase simultaneously so the change volume of empty space in the container is equal to . But in some case volume of empty space does not change such case . In case of gas coefficient of volume expansion is very high in compair with solid and liquid so it apply huge pressure on the container wall while heating. Copressed volume of liquid is calculated by So bulk modulus .
Question may ask: Change in volume with temperature, Volume of empty space of container having liquid with rising in temperature, Ratio of coefficient of volume expansion to make empty space constant at all temperature, based on Relation between bulk modulus and coefficient of expansion.
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4
Patterns: Cooling of body
Discription: Temperature difference derives the heat flow. if two or more surfaces have same surface area, same surface temperature and in same surrounding conditions then heat transfer rate will be same ie . this equation gives idea to compare rate of cooling of two or more different matter. Heat that comes out, comes from loss in internal energy so Q can be written as
During heat transfer, we assume that temperature of surface and centre of an object is same at every instant of time hence temperature decrease uniformly from entire volume. A single body in constant surrounding condition cool faster at high temperature and its cooling rate decrease exponential with its temperature fall. To calculate the time required to cool between different condition range we use either Newton's low of cooling or Approximation formula ie . this method is applicable for a small temperature range.
Question may ask: Comparison in cooling rate of two matters in similar conditions, To calculate cooling time between given temperature range using Newton's law of cooling and Approximation method of an object.
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