Heat Class 7 Extra Questions and Answers

These AP 7th Class Science Important Questions and 3rd Lesson Heat Class 7 Extra Questions will help students prepare well for the exams.

Class 7 Science Heat Extra Questions

Heat Class 7 Important Questions

Question 1.
Define clinical thermometer?
Answer:
The thermometer that measures our body temperature is called a clinical thermometer.

Question 2.
What is the use of kink in clinical thermometer?
Answer:
It prevents mercury level from falling on its own when thermometer is removed from the body.

Heat Class 7 Extra Questions and Answers

Question 3.
Shopkeepers selling ice blocks usually cover them with jute sacks. Explain why.
Answer:
A jute sack is a thermal insulating material and it helps ice not to melt immediately. So, shopkeepers must use insulating materials like sack, saw dust, newspaper etc., to cover the ice.

Question 4.
What is temperature?
Answer:
A reliable measure of the hotness of an object is called its temperature.Temperature is measured by a device called thermometer.

Question 5.
What are the ranges of a clinical thermometer and a laboratory thermometer?
Answer:
The range of a clinical thermometer is generally from 35°C to 42°C
The range of a laboratory thermometer is generally from -10°C to 110°C

Heat Class 7 Extra Questions and Answers

Question 6.
What is a laboratory thermometer?
Answer:
A laboratory thermometer is used for measuring the temperature of substances in a laboratory.

Question 7.
Do all hot bodies radiate heat?
Answer:
Yes, all hot bodies radiate heat.

Question 8.
What are the various methods of transfer of heat?
Answer:
The various methods of transfer of heat are :

  • Conduction
  • Convection
  • Radiation

Question 9.
In a mercury thermometer, the level of mercury rises when its bulb comes in contact with a hot object. What is the reason for this rise in the level of mercury?
Answer:
As the temperature increases, expansion of mercury takes place in the capillary tube which leads to the rise in the level of mercury in thermometer.

Question 10.
Define sea breeze.
Answer:
The flow of cool air from the sea towards the land to replace the hot air on land is called sea breeze. This phenomenon takes place during the day.

Question 11.
Which type of clothes should be preferred in the month of June in India?
Answer:
Light coloured clothes should be preferred in the month of June in India.

Heat Class 7 Extra Questions and Answers

Question 12.
Why dark-coloured clothes are preferred in winter?
Answer:
Dark-coloured clothes are preferred in winter because they absorb most of the heat falling on them and keep us warm.

Question 13.
Name the units of temperature.
Answer:
Temperature is measured in units of degrees Celsius (°C) or degrees Fahrenheit (°F).

Question 14.
Why do we wear woollen clothes during winter?
Answer:
Wool is a poor conductor of heat. Moreover, air is trapped in between the wool fibres which acts as insulator. This air prevents the flow of heat from our body to the cold surroundings. So, woollen clothes keeps us warm during winter.

Heat Class 7 Extra Questions and Answers

Question 15.
How does the transfer of heat to take place in water or air?
Answer:
The transfer of heat to take place in water or air by the process of convection.

Heat Extra Questions

Question 1.
A circular metal loop is heated at point O as shown in figure.
a) In which direction, would heat flow in the loop ?
b) In which order, the pins at points P,Q and R fixed with the help of wax fall if points O, P, Q and R are equidistant from each other?
Answer:
Heat Class 7 Extra Questions and Answers 1
a) The heat will flow in the direction from O to P and O to R .
b) At first the pins at R and P will fall simultaneously. followed by the pin at Q.

Question 2.
It is advised not to hold the thermometer by its bulb while reading it. Explain, why.
Answer:
It is advised not to hold the thermometer by its bulb while reading it because if we hold a thermometer by its bulb, the level of mercury in the bulb increases from the actual reading due to our body temperature.

Question 3.
What is convection?
Answer:
The mode of transfer of heat from the hotter part of a fluid (liquid or gas) to its colder parts by the movement of the liquid (or gas) itself is known as convection. The transfer of heat by convection can take place only in liquids and gases. It is due to the reason that the particles in liquids and gases can move about freely.

The transfer of heat by convection cannot take place in solids because the particles in the solids are fixed at a place and cannot move about freely. It is also not occurred in empty space or vacuum because there are no particles of any kind in empty space which can move and transfer heat.

Heat Class 7 Extra Questions and Answers

Question 4.
Define conduction.
Answer:
The mode of transfer of heat from hotter part of a material to its colder part or from a hot material to a cold material in contact with it, without the movement of material as a whole, is known as conduction. In all the solids, heat is transferred by the process of conduction.

Question 5.
What is radiation ?
Answer:
Radiation is the transfer of heat between objects that are not in direct touch. The two items may be solids or liquids, but they are not in contact. Heat is transferred from a distance when a heated object radiates heat into the environment. There is no need for a medium for radiation. Because it emits heat to the surroundings, a hot object cools down on its own.

Question 6.
While constructing a house in a coastal area, in which direction should the windows preferably face and why?
Answer:
The windows of coastal areas should preferably face in the direction of sea.The sea breeze coming from sea keeps the house cool during the day time.

Question 7.
What is the use of a maximum-minimum thermometer?
Answer:
A maximum-minimum thermometer is used by the weathermen to give weather reports stating the highest and lowest temperature recorded for a particular day.

Question 8.
What are the conductors and insulators of heat ?
Answer:

  • Conductors: The materials which allow heat to pass through them easily are conductors of heat.
    Example : aluminium, iron and copper.
  • Insulators : The materials which do not allow heat to pass through them easily are insulators of heat.
    Example : plastic and wood.

Heat Class 7 Extra Questions and Answers

Question 9.
What are the effects of heat ?
Answer:
The effects of heat are :

  • When an object is heated, then it becomes hotter and may get expand. So, in this heat may change the state of the body like ice can also get change into the water.
  • Heat sometimes acts as a catalyst to speed up the chemical reaction.
  • Heat can even kill the bacteria as well.

Question 10.
Why is mercury preferred in thermometers in place of water?
Answer:
Mercury used due to the following reasons:

  • It has greater visibility than water.
  • It expands uniformly.
  • It does not stick to the walls.
  • It remains liquid at room temperature.
  • It is shiny and easy to see.

Question 11.
At a camp site there are tents of two shades. One made with black fabric and the other with white fabric. Which one will you prefer for resting on a hot summer afternoon? Give reason for your choice. Would you like to prefer the same tent during winter?
Answer:
We will prefer white fabric tent in case of summer as white is a bad absorber and a good reflector of heat. But in case of winter, we should not use white fabric tent, we should use black fabric tent as it absorbs all colours of light from the sun and keeps us warm inside the tent.

Question 12.
Explain the maximum – minimum thermometer and digital thermometer.
Answer:
Maximum – minimum thermometer : It is the thermometer used by the weathermen to give weather reports stating the highest and lowest temperature recorded for a particular day.
Digital thermometer: Mercury is a toxic substance (poisonous substance) and hence it is very difficult to dispose of safely if a thermometer breaks. These days, digital thermometers are available which do not use mercury.

Heat Class 7 Extra Questions and Answers

Question 13.
Differentiate between two modes of transfer of heat, i.e. convection and conduction.
Answer:
Difference between convection and conduction are as follows :

Conduction Convection
1) The mode of transfer of heat from the hotter part material to its colder part or from a hot material to a cold material in contact with it without the movement of material as a whole. So, this phenomenon is known as conduction. 1) The mode of transfer of heat from the hotter part of a fluid to its colder parts by the movement of liquid itself. So, this phenomenon is known as convection.
2) In all the solids, heat is transferred by, the process of conduction. 2) In all the liquids and gases, heat is transferred by the process of convection.

Extra Questions of Heat Class 7

Question 1.
What are the precautions to be taken while reading a clinical thermometer?
Answer:
Following precautions to be taken while reading a clinical thermometer:

  • Thermometer should be washed before and after each use, preferably with an antiseptic solution.
  • Ensure that before use the mercury level is, below 35C
  • Do not wash the thermometer with hot water.
  • Do not hold the thermometer by the bulb while taking the readings because in such cases, the temperature of our hand will also effect the reading.
  • Read the thermometer keeping the level of mercury along the line of sight.
  • Handle the thermometer with care, as you handle any glass articles.

Heat Class 7 Extra Questions and Answers

Question 2.
Explain the structure of a clinical thermometer and state its special features with the help of a diagram.
Answer:
A clinical thermometer consists of a long, narrow, uniform glass tube having a thin and uniform bore.There is a glass bulb at one end of the glass tube which consists of mercury.The kink is present above the bulb. On the glass tube, we can see a temperature scale, usually a celsius scale.
Features:

  • There is a very short range of temperature of a clinical thermometer, i.e., from 35°C to 42°C.
  • A clinical thermometer has a kink in its glass tube which is to prevent the back flow of mercury into the thermometer bulb when the thermometer bulb is removed from the mouth of a patient. This kink prevents the mercury level in the thermometer tube from falling on its own.

Question 3.
Write the differences between heat and temperature.
Answer:
The differences between heat and temperature are as follows :

S.No Heat Temperature
1) It is form of energy in a body of intensity of heat. The temperature of a body is the parameter.
2) The main feature of heat it is that it travels from the hotter region to The temperature increases when heated and temperature falls when cooled.
3) Its SI unit is Joule (J) Its SI unit is Kelvin (K)
4) Calorimeter is used to measure the heat in a body. Temperature can be measured by  the thermometers.
5) It is denoted by Q. It is denoted by T.

Question 4.
How does the heat travel in the air? Explain the sea breeze and land breeze with the help of diagram.
Answer:
Heat travels in the air by convection. The blowing of sea breeze and land breeze in coastal areas is generally occurred due to the convection of heat in air.
Heat Class 7 Extra Questions and Answers 3

Sea breeze: In coastal areas during the day time, the breeze generally flows from the sea towards the land is called sea breeze. The land gets heated faster than water during the day. Due to this, the air over the land becomes hotter and lighter and rises up.Cool air from water rushes in towards land to fill the space. Hence, the windows in coastal areas are made to face the sea to receive the cool sea breezes.

Heat Class 7 Extra Questions and Answers

Land breeze: The breeze blowing from the land towards the sea is called land breeze. During the night, the land loses heat faster than water and becomes cooler and the air over the sea is now warmer due to which, it rises up and the cooler air over the land rushes to take its place. Therefore, we observe a land breeze at night.

Question 5.
What are the different modes of heat transfer ? Explain.
Answer:
Flow of heat from one object to another, whether solid or liquid is called a transfer of heat. Heat always flows from a body at a higher temperature to another body at lower temperature. There are three modes of transfer of heat:

Convection: The mode of transfer of heat from the hotter part of a fluid (liquid or gas) to its colder parts by the movement of the liquid (or gas) itself is known as convection. The transfer of heat by convection can take place only in liquids and gases.

Conduction : The mode of transfer of heat from hotter part of a material to its colder part or from a hot material to a cold material in contact with it, without the movement of material as a whole, is known as conduction. In all the solids, heat is transferred by the process of conduction.

Radiation : It is the transfer of heat between objects that are not in direct touch. The two items may be solids or liquids, but they are not in contact. Heat is transferred from a distance when a heated object radiates heat into the environment. There is no need for a medium for radiation. Because it emits heat to the surroundings, a hot object cools down on its own.

Question 6.
State the precautions to be observed while using a laboratory thermometer.
Answer:
Precautions to be,observed while using a laboratory thermometer.

  • Handle the thermometer with care. If it hits against some hard object, it can break.
  • Thermometer should be kept upright not tilted.
  • The bulb of the thermometer should be surrounded from all sides by the substance of which the temperature is to be measured.
  • The bulb should not touch the surface of the container.
  • Do not move the thermometer while measuring the temperature of the substance.
  • Never hold the thermometer by the bulb while reading it.
  • Read the temperature of the object when the thermometer is in the substance.

Case Based / Data – Based Questions

Srikanth likes to have curd in his lunch. He even knows for that for setting curd, a small amount of curd is added to warm milk. The microbes present in the curd helps in setting the curd, if the temperature of the mixture remains approximately between 35°C to 45°C. But he is worried because it is winter and the room temperature remains a much below the range which makes setting of curd a difficult.

i) Suggest a way to Srikanth to set curd in such a situation.
Answer:
Srikanth can set curd by keeping the container near the gas stove while cooking or keeping the container wrapped in a woollen material or inside a heat resistant container.

Heat Class 7 Extra Questions and Answers

ii) Why setting of curd during winter season become difficult?
Answer:
In winter season, temperature is very low. Low temperature inhibits the activity and the growth of microbes present in the curd and thus making of curd difficult.

iii) What is the temperature of the mixture ?
Answer:
The temperature of the mixture remains approximately between 35°C to 45°C.

Leave a Comment