Calorimetry Flashcards
Internal energy means
Sum of kinetic and potential energy
Heat energy
Form of energy which flows from hot body to cold body
Calorimetry means
measurement of heat
Si unit of heat
Joule
Most commanly used unit of heat , 1 Calorie =
Calorie , Quantity of heat required to raise temp of 1g of water from 14.5 c to 15.5c
Relationship between Cal and joule
1 Cal = 4.186 J
One kilo calorie is
4200J
Unit Kilo calorie is used in
Measuring ENERGY VALUE OF FOOD
what is temp ? si unit of temp
Temperature is a parameter which tells the thermal state of the body . It determines the state of flow of heat .
SI Unit : KELVIN
TK= 273 + t*C
amount of heat energy contained on a body depends on
Mass , Temp , Material of the body
Quantity Of heat absorbed depends on three factors
Amount of heat energy absorbed is directly proportional to the mass of the object
Amount of heat energy absorbed is directly proportional to the rise in temperature
Amount of heat energy absorbed depends on substance of the object
Q -> Charge formula
Q = cm * rise in temp
Heat capacity -> definition , formula , units
The heat capacity of body is amount of heat energy required to raise its temp by 1*C
C’ = Q/ raise in temp
Si unit - JK^-1
Specific heat capacity - definition , unit , formula
Specific heat capacity - The heat capacity of body when expressed in unit mass , Specific heat capacity is amount of heat energy required to raise the temp of unit mass of that substance
c=Q/m*t
Si unit - Joule per kilogram kelvin - JKg^-1 K^-1
1 cal g^-1 C^-1 = __________________
4.2 * 10^3 Jkg^-1 K^-1
How we determine Good and bad conductor’s of heat ?
If it has low specific heat capacity its a good conductor of heat
If it has high specific heat capacity its a bad conductor of heat
Copper - 0.4 J/gK , H2O - 4.2J/gK
Specific heat capacity is maximum in
various types of water and its c
Hydrogen - 14630 J/kgK
Stream - 460 J/kgK
Ice-2100 J/kgK
Water-4200 J/kgK
What is calorimeter ?
Calorimeter is a cylindrical vessel which is used to measure the amount of heat energy lost or gained by the body when it is mixed with another body or substance .
Calorimeter ? how it is made ?
It is made up of thin sheet of copper
Outer and Inner surface of vessels are polished - to reduce the heat loss due to radiation .
It is placed inside a wooden jacket - For insulation
Space between calorimeter and jacket filled with poor conductor such as wool , cotton - To avoid heat loss by conduction
Covered with wooden lid - To avoid heat loss by convection
Has 2 holes - one for stirrer another for thermometer
Why calorimeter is made up of thin sheet of copper ?
Copper good conductor of heat so the vessels soon acquires the temperature of its contents
Copper has low specific heat capacity so the amount of heat energy taken by the calorimeter to acquire its temperature is very small
What is principal of method of mixtures ?
If no energy is lost in surroundings
Heat energy lost by hot body = Heat energy gained by cold body
The equation of principal of calorimeter
m1 c1 [t1-t] = m2 c2 [ t-t2]
Hot water bottles are used for fomentation
reason is that water does not cool quickly due to its high specific heat capacity , so hot water body provide heat energy for fomentation over a long period
Water is used as an effective coolant
due to its high specific heat capacity , water can absorb high heat energy without much rise in temperature . This is why radiators in car and generators use water for cooling.
In cold countries water is used as heat reservoir for wine and juice bottles to avoid freezing
Due to its high specific heat capacity water imparts large amount of heat before reaching freezing point . Hence bottle kept in water remain warm and they donot freeze
Farmer fill their field with water to protect crop from frost
On cold night , the surrounding temperature falls below 0C
Water in the fine capillaries will freeze so the plant will burst due to increase in volume of water on freezing . To avoid this Farmers fill their field with water [High specific heat capacity] which does not allow surrounding temperature to fall below 0C .
All animals and plant have high content of water in their body :
About 80% to 90% , which helps to maintain same temperature in all seasons
why base of electric pan and electric press is made thick and heavy ?
by making it thick we can increase the heat capacity
Change of phase means
The process of change from one state to another at a constant temperature
What is mean by vaporisation ? condensation ? solidification ?
sublimation ?
Vaporisation - Liquid to vapour
Condensation - Vapour to liquid
Solidification - Gas to solid
Sublimation - Solid to gas
Molecules posses kinetic energy by
and
Molecules Posses Potential energy by
Kinetic energy due to their random motion
Potential energy due to their molecular attractive forces
What is melting ?
Change from solid to liquid phase by the absorption of heat at CONSTANT temperature
Melting point means
Constant temperature at which solid changes to liquid
Freezing means
reverse change from liquid to solid phase with liberation of heat at constant temperature
Freezing point
the temperature at which liquid changes to solid
for pure substance how the melting point and freezing point will be
Identical
For given mass of substance the amount of heat energy absorbed during melting is ____________ as that during freezing
Same
Which substances expand on heating ?
Lead and wax
Melting point of substances which contract on
melting decreases by the increase in pressure
Melting point of the substances which expand on melting
Increase in increase in pressure
Effect of impurities on the melting point
Melting point of substances decrease by the presence of impurities in it
Melting point of ice decreases from
0C to -22C
