Calorimetry Flashcards
define thermal energy
the total internal energy of all the molecules of a substance
define heat
heat is that form of energy that flows from a hot body to a cold body when the two are kept in contact
define 1 calorie
the heat energy required to raise the temperature of 1 g of water from 14.5 C to 15.5 C
define temperature
parameter which tells us the degree of hotness or coldness of a body. it determines the direction of flow of heat when two bodies of different temperatures are kept in contact
factors affecting quantity of heat absorbed to increase temperature of a bodY
- mass of body (direct)
- increase in temperature of body (direct)
- material of body
temperature depends on
average kinetic energy of its molecules due to their random motion
define heat capacity
amount of heat energy required by a body to raise its temperature by 1 C
heat capacity C’=
amount of heat energy supplied Q/ rise in temperature t
define specific heat capacity
specific heat capacity of the substance is the amount of heat energy required to raise the temperature of unit mass of that substance by 1 C
specific heat capacity c=
= heat capacity of the body C’/ mass of the body m
= C’/ m * rise in temp
unit of specific heat capacity
J/ kg.K
relation between C’ and c
C’ = m * c
does specific heat capacity depend on mass of the body
no, does not depend on mass as it is a characteristic property of the substance of the body
specific heat capacity of good conductors of heat
low c
calorimeter
cylindrical vessel which is used to measure the amount of heat gained or lost by a body when it is mixed with another body or substance
why is calorimeter made of a thin sheet of copper
- copper is a good conductor of heat so vessel soon acquires temperature of contents
- copper has low specific heat capacity so amount of heat taken by the calorimeter itself is very low
why are outer and inner surfaces of calorimeter polished
reduce heat loss by radiation
why is calorimeter placed inside a wooden jacket
for insulation
why is space between calorimeter and wooden jacket filled with some poor conductor
to reduce heat loss by conduction
why is calorimeter covered by a wooden lid
to reduce heat loss by convection
principal of method of mixtures/ principal of calorimetry
heat energy lost by the hot body= heat energy gained by the cold body (this is based on law of conservation of energy)
m1.c1.(t1-t)= m2.c2.(t-t2)
heat energy gained by calorimeter which mixing A and B
Mass of calorimeterspecific heat capacity of its substance(t-t1)
why is climate near the sea moderate
specific heat capacity of water is very high, and of sand it is very low. Hence, the heat energy required for the same rise in temperature for water is five times of that of sand. Hence, sand gets heated or cooled more rapidly than water. This difference in temperature sets up a convection current.
why are hot water bottles used for fomentation
specific heat capacity of water is high, so it takes more time to cool down. hence, hot water bottle provides more heat energy for fomentation
