Heat: Class 7 Science Q&A
21 free answers on Heat (Science) for Class 7 students, across CBSE, ICSE and State boards. Includes questions such as “Why is it advised not to hold the thermometer by its bulb while reading it?”, “Shopkeepers selling ice blocks usually cover them with jute sacks. Explain why.”, “Give two examples each of conductors and insulators of heat.”
Question & Answer
Questions
- ScienceClass 7CBSE
While constructing a house in a coastal area, in which direction should the windows preferably face and why?
Soln: The windows of houses in coastal areas should preferably face towards the sea as sea breeze will keep it cool during day time.
- ScienceClass 7CBSE
At a campsite, 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 a reason for your choice. Would you like to prefer the same tent during winter?
Soln: In summer I would choose a tent with white colour fabric as white is a bad absorber and a good reflector of Heat. But in winter I would choose a tent with black colour fabric as black is a good absorber and bad reflector of heat.
- ScienceClass 7CBSE
Why is it advised not to hold the thermometer by its bulb while reading it?
Soln: If we hold the thermometer by its bulb while reading it, the mercury will get expanded by our body temperature.
- ScienceClass 7CBSE
You may have noticed that a few sharp jerks are given to clinical thermometer before using it. Why is it done so?
Soln: The jerk will allow the mercury flow into the bulb above kink, which will make mercury level below normal temperature.
- ScienceClass 7CBSE
For setting curd, a small amount of curd is added to warm milk. The microbes present in the curd help in setting if the temperature of the mixture remains approximately between 35°C to 40°C. At places, where room temperature remains much below the range, the setting of curd becomes difficult. Suggest a way to set curd in such a situation.
Soln: In order to maintain the desired temperature container with curd should be wrapped with woollen or any other insulator. Curd can also be set in a room with temperature below optimum by keeping the container near the gas stove.
- ScienceClass 7CBSE
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?
Soln: Mercury gets expanded on heating; hence its level rises in the capillary when it comes in contact with a hot object.
- ScienceClass 7CBSE
To keep her soup warm Paheli wrapped the container in which it was kept with a woollen cloth. Can she apply the same method to keep a glass of cold drink cool? Give a reason for your answer
Soln: Yes, the woolen cloth can be used to keep a glass of cold drink cool because woollen is an insulator that will not allow escape or entry of heat.
- ScienceClass 7CBSE
Shopkeepers selling ice blocks usually cover them with jute sacks. Explain why.
Soln: Shopkeepers selling ice blocks usually cover them with jute sacks because materials like jute sacks sawdust and newspapers act as insulators and cannot allow escape or entry of heat through them.
- ScienceClass 7CBSE
Paheli and Boojho measured their body temperature. Paheli found her’s to be 98.6 °F, and Boojho recorded 37°C. Which of the following statement is true? (a) Paheli has a higher body temperature than Boojho. (b) Paheli has a lower body temperature than Boojho. (c) Both have a normal body temperature. (d) Both are suffering from fever.
Soln: The answer is (c) Both have normal body temperature. Explanation: Degree Celsius and Fahrenheit are two scales of temperature measurement. Normal body temperature is 37º which is equal to 98.6 F. Hence both of them have normal body temperature.
- ScienceClass 7CBSE
A beggar wrapped himself with a few layers of newspaper on a cold winter night. This helped him to keep himself warm because (a) friction between the layers of newspaper produces heat. (b) air trapped between the layers of newspaper is a bad conductor of heat. (c) newspaper is a conductor of heat. (d) newspaper is at a higher temperature than the temperature of the surrounding.
Soln: The answer is (b) air trapped between the layers of newspaper is a bad conductor of heat. Explanation: The heat from his body will not escape into the surroundings, and this will help him to keep his body warm.
- ScienceClass 7CBSE
A marble tile would feel cold as compared to a wooden tile on a winter morning because the marble tile (a) is a better conductor of heat than the wooden tile. (b) is polished, while the wooden tile is not polished. (c) reflects more heat than the wooden tile. (d) is a poor conductor of heat than the wooden tile.
Soln: The answer is (a) is a better conductor of heat than the wooden tile.
- ScienceClass 7CBSE
. Stainless steel pans are usually provided with copper bottoms. The reason for this could be that (a) copper bottom makes the pan more durable. (b) such pans appear colourful. (c) copper is a better conductor of heat than stainless steel. (d) copper is easier to clean than stainless steel.
Solution: The answer is (c) copper is a better conductor of heat than stainless steel.
- ScienceClass 7CBSE
A wooden spoon is dipped in a cup of ice cream. Its other end (a) becomes cold by the process of conduction. (b) becomes cold by the process of convection. (c) becomes cold by the process of radiation. (d) does not become cold.
Solution: The answer is (d) does not become cold because wood is a bad conductor of heat.
- ScienceClass 7CBSE
An iron ball at 40°C is dropped in a mug containing water at 40°C. The heat will (a) flow from the iron ball to water. (b) not flow from the iron ball to water or from water to the iron ball. (c) flow from water to the iron ball. (d) increase the temperature of both.
Solution: Answer is (b) not flow from the iron ball to water or from water to the iron ball because both of them have the same temperature of 40°C.
- ScienceClass 7CBSE
One litre of water at 30°C is mixed with one litre of water at 50°C. The temperature of the mixture will be (a) 80°C (b) more than 50°C but less than 80°C (c) 20°C (d) between 30°C and 50°C
Solution: The temperature of the mixture will be between 30°C and 50°C because hot water loses heat and simultaneously cold water gains heat. This keeps the temperature in between 30°C and 50°C.
- ScienceClass 7CBSE
. In places of hot climate it is advised that the outer walls of houses be painted white. Explain.
Solution: In places of hot climate, it is advised that the outer walls of houses be painted white because white colour reflects back most of the heat that is incident on it, as white is a poor absorber of heat. This helps in keeping the house cool.
- ScienceClass 7CBSE
Discuss why wearing more layers of clothing during winter keeps us warmer than wearing just one thick piece of clothing.
Solution: More layers of clothing during winter keeps us warmer than wearing just one thick piece of clothing because air gets trapped in between the layers. As air is a bad conductor of heat it does not allow the heat to escape from the body.
- ScienceClass 7CBSE
Match the following: Column-I Column-II (i) Land breeze blows during (a) summer (ii) Sea breeze blows during (b) winter (iii) Dark coloured clothes are preferred during (c) day (iv) Light coloured clothes are preferred during (d) night
Solution: Column-I Column-II (i) The land breeze blows during (d) night (ii) The sea breeze blows during (c) day (iii) Dark coloured clothes are preferred during (b) winter (iv
- ScienceClass 7CBSE
Fill in the blanks : (a) The hotness of an object is determined by its __________. (b) Temperature of boiling water cannot be measured by a _____________ thermometer. (c) Temperature is measured in degree ______________. (d) No medium is required for transfer of heat by the process of __________. (e) A cold steel spoon is dipped in a cup of hot milk. Heat is transferred to its other end by the process of ______________. (f ) Clothes of ______________ colours absorb heat better than clothes of light colours.
Solution: (a) The hotness of an object is determined by its temperature. (b) Temperature of boiling water cannot be measured by a clinical thermometer. (c) Temperature is measured in degree Celcius. (d) No medium is required for transfer of heat by the process of radiation. (e) A cold steel spoon is dipped in a cup of hot milk. Heat is transferr
- ScienceClass 7CBSE
Give two examples each of conductors and insulators of heat.
Solution: Conductors: Iron and copper Insulators: Plastic and wood