Temperature, Heat and Internal Energy

Energy transfer by heating

Temperature, Heat and Internal Energy

Relation between them

Water

Mass m

HeatTransfer E

TemperatureChange T

Temperature, Heat and Internal Energy

Relation??

Mass mBy triple beam balance

Heat Transfer E : As E = P t, time for Heating indicates how much energy is transferred.

Temperature Change TDirectly recorded from a thermometer

Temperature, Heat and Internal Energy

E (proportional to time of heating) / min

0 1 2 3 4 5 6

T / oC 20.0 31.4 42.9 54.3 65.7 77.1 88.6

T / oC 0 11.4 22.9 34.3 45.7 57.1 68.6

E T for fixed same mass m

E

T

Temperature, Heat and Internal Energy

Mass of water / kg

0.25 0.25 0./75 1.0

Energy transfer E /s

53 104 155 211

E

m

E m for fixed same temp increase T

Temperature, Heat and Internal Energy

E T for fixed same mass m

E m for fixed same temp increase T

E m T

E = c m T where c is a proportional constant

Specific heat capacity c = E / m T

c = 1J kg-1 oC-1 or 1 J kg-1 K-1 certain material

means energy needed to increased the temperatureof 1kg the material by 1 oC is 1 J.

Temperature, Heat and Internal Energy

Specific heat capacityDepends on the nature of material

Substance Specific heat capacity / J kg-1 oC-1

water 4200

Alcohol 2500

Aluminium 900

Glass 600

Iron 480

Copper 370

Mercury 140

Temperature, Heat and Internal Energy

heat capacity

1. Unit : J oC-1 or J K-1

2. C = mc

Same specific heat capacity

But different heat capacity

C = E / T

Temperature, Heat and Internal Energy

Specific heat capacity

Pg. 170, Qn (1 – 6)

Temperature, Heat and Internal Energy

Measurement of s.h.c. of water

* Design of experiment and Setup

E = m c T

Temperature, Heat and Internal Energy

Measurement of s.h.c. of water

* Design of experiment and Setup

* Precautions

* Data and Data Analysis

For safety measure:Do not switch on the heater unless it is immersed in water.

Temperature, Heat and Internal Energy

* Precautions1. Avoid energy lost to the surrounding by (a) totally immersing the heater in the water, (b) using polystyrene cup, (c) using thermometer, stirrer, heater and container of small s.h.c.

2. Ensure correct temperature is recorded by (a) taking readings while a maximum attained (b) stirring the water to have uniform temp.

3. The mass is correctly recorded by * using a lid to prevent water from getting out.

Temperature, Heat and Internal Energy

Measurement of s.h.c. of aluminium

* Design of experiment and Setup

E = m c T

Temperature, Heat and Internal Energy

Measurement of s.h.c. of aluminium

* Design of experiment and Setup

* Precautions

* Data and Data Analysis

For safety measure:Do not switch on the heater unless it is immersed in water.

Temperature, Heat and Internal Energy

* Precautions

1. Avoid energy lost to the surrounding by (a) adding a few drop of oil to the holes in the Al block to ensure good contact, (b) placing the block on a polystyrene title,

• Ensure correct temperature is recorded by * taking readings while a maximum attained

Temperature, Heat and Internal Energy

Mesaurement of s.h.c.

Improvements ?

Temperature, Heat and Internal Energy

mixtures

A B

High temp Low temp

Energy lost in A = Energy gain in B

If there is no energy loss

Temperature, Heat and Internal Energy

Example of mixture

T??

Energy lost by hot water= mc T= (0.4)(4200)(80 – T)

Energy lost by cold water= (0.3)(4200)(T - 10)

A B A B0.4 kg80oC

0.3 kg10oC

(0.4)(4200)(80 – T) = (0.3)(4200)(T - 10)

T = 50oC

Temperature, Heat and Internal Energy

High s.h.c. of water

Good Coolant

Temperature, Heat and Internal Energy

High s.h.c. of water

Cooler in summer and milder in winter

Temperature, Heat and Internal Energy

High s.h.c. of water

Watery fluid in human body