Heat and Its Effect Questions & Answers

Hi Everyone!! This article will share Heat and Its Effect Questions & Answers.

In my previous post, I have shared the Objective Type Questions & Answers of Heat and Its Effect so, make sure to check that post as well.

Heat and Its Effect Questions & Answers

Question 1: Define conduction, convection and radiation.

(a) Conduction

Answer: It is the process of heat transfer along a body from one molecule to another, without actual motion of molecules. For example – heating of metal handle of a pan.

(b) Convection

Answer: It is the process by which heat is transmitted through liquid and gases from places of higher temperature to places of lower temperature by actual movement of molecules. For example – heating of water in a pan.

(c) Radiation

Answer: It is the process by which heat is transferred from one body to another along straight lines without affecting the intermediate medium. For example – in microwave the food gets heated without heating the intermediate medium.

Question 2: What is temperature? Name the different temperature scales.

Answer: Temperature is the degree of hotness or coldness of an object. Different temperature scales are Celsius scale, Fahrenheit scale, Kelvin scale.

Question 3: What are insulators? Give two examples.

Answer: Materials that do not allow heat to be transferred through them are called insulators. For examples wood, plastic.

Question 4: Why is heat considered a form of energy?

Answer: As heat has the capacity of doing work it is said to be a form of energy. For example, the working of the pressure cooker – when the water is heated for some time, we hear the whistle. The weight on a nozzle gets lifted and some steam gushes out.

Question 5: What is the difference between heat and temperature?

Answer:

Question 6: Differentiate between conductors and insulators.

Answer: Materials that transfer heat easily are called conductors; example of good thermal conductor is metal. Due to this, metal is used to make utensils for cooking food.

Materials that slow the transfer of heat are called insulators; example of good thermal insulator is wool. Due to this, wool is used to make winter clothing like coats, scarves, gloves, etc.

Question 7: Write two conditions necessary for conduction of heat.

Answer: The two bodies should be in solid state and the two bodies should be in contact or touch each other.

Heat and Its Effect Questions & Answers

Question 8: Write the relation between Celsius and Fahrenheit scales. Convert 40^o C into F and 93^o F into C.

Answer: The relation between Celsius and Fahrenheit can be mathematically expressed as

F = (9/5*C) + 32 or

C = 5/9(F−32)

Where, F is the temperature in Fahrenheit, C is the temperature in Celsius (Centigrade scale).

Converting 40^o C to F

F = (9/5 x C) + 32

F = (9/5*40) + 32

F = (72) + 32

F = 104

Hence, 40^o C is equal to 104^o F.

Converting 93^o F to C

C = 5/9 (F – 32)

C = 5/9 (93 – 32)

C = 5/9 (61)

C = 33.88

Hence, 93^o F is equal to 33.88^o C.

Question 9: What is the advantage of the constriction found in a clinical thermometer?

Answer: The constriction prevents the mercury from contracting and flowing back to the bulb and enables us to read the temperature of the body after the thermometer has been taken out from the mouth.

Question 10: How do woollen clothes keep us warm in winters?

Answer: Woollen clothes are bad conductor of heat. They do not allow heat to escape from body, thus keeping us warm.

Question 11: Discuss the effect of heat on matter.

Answer: Heat has the following effects:

• It results in an increase in temperature – When heat energy is added, its temperature increases, for example, when we heat water, it gets warm and its temperature increases.
• It may result in change of state – When solid changes to a liquid or a liquid change to a gas, the temperature does not change while the change of state is taking place.
• It causes things to expand – Most of the materials expand on heating and contract on cooling. All three states of matter expand on heating.

Question 12: State the reasons why mercury is commonly used in thermometers.

Answer:

• Mercury is used as a thermometric liquid as it has a lower freezing point (-39^o C) and a high boiling point (35^o C). Hence it can be used over a wide range of temperature.
• It is shiny liquid metal, hence can be easily seen through the glass of the thermometer tube.
• It has a fairly large expansion for a small change in temperature.
• It does not stick to the glass tube.

Question 13: Explain the construction of a clinical thermometer.

Answer:

• Clinical thermometer is used to measure the temperature of human body.
• The scale used to measure the temperature is known as Celsius scale denoted by ^oC or Fahrenheit denoted by ^oF.
• It reads temperature from 35^o C to 42^o C or from 94^o F to 108^o F.
• It consists of a long, slender and uniform glass tube with a bulb at one end containing mercury.
• There is a small shining thread of mercury outside the bulb.
• There is a kink near the bulb which prevents mercury level from falling on its own.

Heat and Its Effect Questions & Answers

Question 14: Explain with the help of an example that solids expands on heating.

Answer:

• Thermal expansion in solids can be understood with the ball and ring experiment.
• Take a metal ball and a ring, the diameter of the ball should be such that it just passes through the ring.
• Heat the ball for some time over a burner.
• Try to pass it through the ring.
• It is observed that the ball does not pass through the ring. This is because the volume of the metal ball increases on gaining heat energy. The increase in the volume of matter on gaining heat energy is called expansion or thermal expansion.

Question 15: Give some applications of radiation.

Answer:

• Solar cooker is the best example of radiated heat coming from the sun, the mirrors installed in it reflect radiation.
• Solar water heaters also work on the principle of radiation
• The principle of radiation is used in electric room heater
• In cold and hilly areas, the outer walls and roofs are usually painted dark to keep the house warm.

Question 16: How can you say that liquids transfer heat by the process of convection?

Answer: Take a round bottom flask (if flask is not available a beaker can be used). Fill it two-thirds with water.  Place it on a tripod, or make some arrangement to place the flask in such a way that you can heat it by placing a candle below it.
Wait till the water in the flask is still. Place a crystal of potassium permanganate in the flask gently using a straw. Now, heat the water by placing the candle just below the crystal.
When water is heated, the water near the flame gets hot. Hot water rises up. The cold water from the sides moves down towards the source of heat. This water also gets hot and rises and water from the sides moves down. This process continues till the whole water get heated. This mode of heat transfer is known as convection.

Question 17: Explain the construction and working of a thermos flask.

Answer: A thermos flask maintains the temperature of the substance kept in it, i.e., it keeps a hot substance hot and cold substance cold for long a long time. The outer casing of a thermos flask is made up of plastic or metal. Plastic, being a poor conductor of heat, acts as an insulator preventing the heat loss through conduction. Inside it, is a double-walled container made of glass or stainless steel. Both the walls are polished so they are shiny. The space between the two walls is a vacuum; this prevents heat loss through convection since there are no airparticles to carry out the transfer of heat. The shiny surface of the walls also prevents heat loss due to radiation.

Question 18: What is the difference between sea breeze and land breeze?

Answer:

So, these were Heat and Its Effect Questions & Answers.