To Study the Factors Affecting the Rate of Loss of Heat of the Liquid

Temperature difference: Large the difference in temperature of the liquid to the surrounding more will be the rate of cooling) so increasing the temperature is proportional to the rate of reaction taking place.

In this experiment, we will go through the factors affecting the rate of heat loss of liquid or on which factors the rate of cooling of a liquid depends. The factor affecting the temperature of any body or rate of reaction is

Cooling medium: In the conduction process rate of cooling is very fast, while a very slow rate of cooling occurs in the convection process as in this movement, actual movement of medium particles takes place.

Surface area: Larger the surface area, fast will be the rate of cooling or the rate of loss of liquid and vice versa.

Thermal conductivity: Thermal conductivity of material decides the loss of heat in the surrounding. Good conductors (black painted material), conduct more heat and thus increase the rate of cooling and rate of loss of heat of liquid and vice versa.

Surface Tension Depends on Which Factors?

Lists the factors affecting the surface tension: With the increase of temperature, the surface starts to decrease as the force between liquid starts to decrease from the surface of the liquid container thus the rate of reaction increases and the reaction proceeds in the forward direction. List the factors affecting the surface tension, temperature,  surrounding environment, and nature of the liquid.  

Table of Content

• Aim

• Apparatus Required

• Theory

• Procedure

• Observation

• Graph

• Result

• Precautions

• Lab Manual Questions

• Viva Questions

• Practice-Based Questions

Aim

To study the factor on which the rate of loss of heat of liquid depends.

Apparatus Required 

• Two Calorimeters A and B of Different Areas (Within Double-Spaced Enclose)

• Two Stands for Support Thermometers

• Two Thermometers

• A Burner to Heat Water

• A Stopwatch

• Stirrer

• Wooden Lids to Close the Two Calorimeters

• Liquid (Water)

Theory

According to Newton’s Law of Cooling, the rate of loss increases with an increase in a temperature difference (temperature of liquid – temperature of surrounding) or increasing the temperature is proportional to rate of reaction and vice versa. In other words, we can say that rate of loss of heat (rate of cooling) is directly proportional to temperature differences such as

\[dQ/dt\text{ }\propto (T-T_{\circ})\]

\[dQ/dt\text{ }=\text{ }K(T-T_{\circ})\]

Where dQ/dt is the rate change of heat, K is the proportionality constant, T is the temperature of the liquid and \[T_{\circ} \]is the temperature of the surroundings.

Diagram

Physics experiment– Factor affecting the rate of loss of heat of the liquid Heating rate has a great influence on the curve.

Procedure

1. In the first step to set up the calorimeter fill the enclosure by filling the space between the double wall with water.

2. Now add two third hot (about \[80{}^\circ C\]) water in the two calorimeters (A and B).

3. Put the calorimeter inside the enclosure and stirred hot water constantly so that heat spreads uniformly. And cover the calorimeter with a wooden lid to resist the escape of heat of the calorimeter.

4. Now support the thermometer through the stand. One thermometer is inside the enclosure and another one is inside the two third water of the calorimeter.

5. Note the least count of both the thermometer and stopwatch (graph between time and temperature) and set the stopwatch at 0.

6. Initially notice the temperature of the water inside the calorimeter (with constantly starring) and enclosure.

7. As soon as the temperature of the water reaches about \[70{}^\circ C\], (at starting temperature falls rapidly) note that reading and start the stopwatch.

8. With constantly stirring notes the temperature of the water after every minute and note the enclosure temperature after every five minutes.

9. At the point where the falling temperature of the water becomes slow, start to take readings of temperature after two minutes and then after 5 minutes.

10. As soon as the temperature falls very slow, stop reading and plot the graph for temperature which indicates the heating rate has great influence on the curve.

Activity 1: Follow the process for one small and one large area calorimeter (different surface area of calorimeter) with the same water and the same volume of water.

Activity 2: Follow the same steps for the two same calorimeters which are black-painted outside (different material) for the same water and its volume.

Activity 3: Follow the same step for the same volume of water in similar calorimeters of different materials (conductivity difference).

Observations

The least count of enclosure water thermometer= -------- \[{}^\circ C\]

Least count calorimeter water thermometer = ---------\[{}^\circ C\]

The least count of stopwatches = -------- s

Table for Activities

Graph

Heating rate has a great influence on the curve. Greater the surface area (area factor), dark painted calorimeter (nature of surface) and conduction material or metallic material (material of surface), all cause higher rate of cooling or increase rate of loss of heat.

Result

• Activity 1: The rate of cooling of liquid increases with an increase in the surface area of the calorimeter (so that more heat can transfer) and vice versa. Thus the rate of cooling liquid is directly proportional to the surface area of the calorimeter.

• Activity 2: The rate of cooling also depends on the nature of the colorimeter. The black of printed calorimeters increases the rate of cooling (as black color is a good absorber and good emitter).

• Activity 3: The rate of loss of heat is directly proportional to the conductivity of the material (calorimeter). Large the conductivity of material, more heat will transfer and thus, the rate of cooling increases and vice versa.

Precautions

1. The thermometer in calorimeter water and enclosure water should not touch to the bottom of the material.

2. Don’t forget to start the hot water to cool it uniformly, keep your eyes on the stop clock and start the stop clock around \[70{}^\circ C\].

Lab Manual Questions 

1. What factors affect the rate of loss of liquid?

Ans: Area, nature and material of the calorimeter affects the rate of loss of liquid.

2. What are the types of heat loss?

Ans: Heat loss through conduction, convection and radiation.

3. Can the rate of loss of liquid be the same for two liquids?

Ans: Yes, the rate of reaction can be the same for two liquids if material, nature, and area of calorimeter and all conditions are the same for two liquids.

4. Lists the factors affecting the surface tension.

Ans: Temperature, nature of given liquid and surrounding environment are the factors which mainly affect the surface tension.

5. Very slow rate of cooling occurs in which process?

Ans: In convection process

Viva Questions 

1. What is the unit of heat loss?

Ans: Heat loss is measured as Watts.

2. Is heat loss negative or positive?

Ans: Heat loss is negative while heat evolved is positive.

3. Does thickness affect heat loss?

Ans: Yes,  greater the thickness of material less will be the rate of heat loss and vice versa.

4. Two variables needed to draw the graph for heat loss?

Ans: Graph of heat loss (heating rate has a great influence on the curve) is determined by change in temperature with time or can say temperature and time are the two variables which are needed for a graph for heat loss.

5. Very slow rate of cooling occurs in which process?

Ans: In the conduction process rate of cooling is very fast while very slow rate of cooling occurs in the convection process as in this movement actual movement of medium particles takes place

6. How does a lid prevent heat loss?

Ans: Lid helps to close the path for heat transfer or can say lid acts as an insulation so that rate of heat loss decreases.

7. Which material is best at conducting heat?

Ans: Most metals are very good conductors of heat or can say material with free electrons conduct heat easily as compared to material without or less free electrons.

8. Boiling of water is what type of heat loss?

Ans: Convection in which water molecules move from high pressure region to low pressure region.

9. On which factor does cooling of water depend?

Ans. Temperature difference, thermal conductivity, surface area, medium, and surface tension.

10. Surface tension depends on which factors?

Ans. List the factors affecting the surface tension, 

temperature,  surrounding environment, and nature of liquid.  

Practical Based Questions 

1. Heat transfer takes place according to which of the following laws?

a. Newton’s second law of motion

b. First law of thermodynamics

c. Newton law of cooling

d. Second law of thermodynamics

Ans: Second law of thermodynamics.

2. For conduction heat transfer, the heat energy propagation will be minimal for

a. Copper

b. Air

c. Water

d. Lead

Ans: Air

3. Heat is transmitted from higher to lower temperature by actual movement of molecules in

a. Convection

b. None of these

c. Conduction

d. Radiation

Ans: Convection

4. Good absorber of heat are

a. Poor emitter

b. Good emitter

c. Non emitter

d. None of these

Ans: Good emitter

5. 300 gm of water at \[25{}^\circ C\] is added to 100g of ice at \[0{}^\circ C\] . The final temperature of the liquid is

a. \[0{}^\circ C\]

b. \[5{}^\circ C\]

c. \[15{}^\circ C\]

d. \[25{}^\circ C\]

Ans: \[0{}^\circ C\]

6. The heat of sun come to earth through

a. Convection

b. Conduction

c. Radiation

d. Evaporation

Ans: Radiation

7. Among the following method, gravity does not play any role in 

a. Convection

b. Radiation and conduction

c. Radiation

d. Conduction and convection

Ans: Radiation and conduction

8. Rate of conduction of heat depends on

a. Area of cross section

b. Temperature difference

c. Properties of material 

d. All of these

Ans: All of these

Conclusion/Summary

With the increase in surface area which is in contact with the hot body will increase the rate of loss of heat or rate of cooling by allowing the large number of vibrating and hot molecules or atoms. And also if the material is conducting then the heat transfer and rate of heat loss increases and the body cools down easily. Also, the color of the material affects the rate of cooling. Black color (as black body) has tendency to absorb whole heat radiation and thus cool down the body which is in contact with it (increases the rate of cooling).