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Heat, Temperature, and Humidity [ Physical Science] [ Science Set 10]| UPPSC Prelims PYQ of Last 30 Years |Important | Objective Question Answer, MCQ and QUIZ

1. The atmosphere exerts enormous pressure on us. But, we do not feel it because

a) Our blood exerts a pressure slightly more than that of the atmosphere

b) We are used to it

c) Our bones are very strong and can withstand the pressure

d) The surface area of our head is very small


Answer. a) Our blood exerts a pressure slightly more than that of the atmosphere;

Our bodies have internal and external pressure that balances the atmospheric pressure, preventing us from feeling it.


2. Food gets cooked faster in a pressure cooker because

a) Water starts boiling at a lower temperature due to high-pressure

b) Water starts boiling at a higher temperature due to high-pressure

c) Water boils only at 100 degrees centigrade but the heat content is higher at high pressure

d) Convection currents are hot inside the pressure cooker


Answer. b) Water starts boiling at a higher temperature due to high pressure;

Food cooks faster in a pressure cooker because the sealed environment traps steam and increases the pressure inside. This elevated pressure raises the boiling point of water, allowing food to cook at higher temperatures, thus reducing cooking time.


3. Maximum  temperature inside pressure cooker depends on-

a) Area of the hole on the top and weight kept on it

b) Area of the hole on the top and food being cooked

c) Weight kept on the hole at the top and food being cooked

d) Area of the hole on the top only


Answer. a) Area of the hole on the top and weight kept on it


4. What changes will the volume of water if the temperature is lowered from 9 degrees C to 3 degrees C-

a) The volume will not change

b)The volume will first increase and then decrease

c) The volume will first decrease and then increase

d) Water will freeze


Answer. c) The volume will first decrease and then increase;

When we lower the temperature of water from 9 degrees Celsius to 3 degrees Celsius, the volume of the water will generally decrease. This is because water follows a specific temperature-density relationship. As the water cools, it becomes denser and contracts, which means its volume decreases. However, this contraction is not linear, especially near its freezing point.

Water has its maximum density at around 4 degrees Celsius, meaning it is the densest at this temperature. As we cool it further from 4 degrees Celsius down to 3 degrees Celsius, there will be a slight decrease in volume due to its increased density, but the change will be relatively small compared to the overall volume change that occurs when water freezes into ice.


5. When a bottle is filled with water and it is freezing the bottle breaks down, because

a) Water expands upon freezing

b) Bottle shrinks at freezing point

c) The temperature outside the bottle is higher than inside

d) Water expands on heating


Answer. a) Water expands upon freezing;

When a bottle filled with water freezes, it can break due to the expansion of water as it turns into ice. Water is unique in that it expands when it freezes, unlike most substances that contract when they solidify. As water cools and freezes, it forms a crystalline structure with a lower density than liquid water.

This expansion can exert significant pressure on the walls of the bottle, and if the bottle is not designed to withstand this pressure, it can crack or shatter. This is why it's important to use bottles designed for freezing liquids, like those made of materials that can expand slightly or withstand pressure, such as glass or certain types of plastic.

In general, glass bottles are more likely to break when freezing compared to plastic bottles, as glass is more rigid and less able to accommodate the expansion of ice. To prevent bottles from breaking when freezing, it's advisable to leave some space for expansion or use containers designed for freezing liquids.


6. Consider the following statements-

Assertion A- If Ice collects in the freezer, the cooling in the refrigerator is affected adversely

Reason R- Ice is a poor conductor

Select the correct answer using the codes given below-

Code-

a) Both A and R are true, and R is the correct explanation of A

b) Both A and R are true, but R is not the correct explanation of A.

c) A is true, but R is false

d) A is false, but R is true


Answer. a) Both A and R are true, and R is the correct explanation of A ;

Yes, if ice builds up in the freezer compartment of a refrigerator, it can adversely affect the cooling efficiency of the refrigerator. Here's how it happens:

Reduced Airflow: Ice buildup can obstruct the airflow within the freezer and refrigerator compartments. This obstruction prevents cold air from circulating properly, which means less cold air is available to keep the refrigerator cold.

Insulation Effect: Ice acts as an insulator. When there's a thick layer of ice on the freezer walls or coils, it can insulate the freezer, making it work harder to maintain its temperature. This increased workload can lead to reduced overall cooling efficiency in both the freezer and the refrigerator.

Longer Running Time: To compensate for the reduced cooling efficiency, the refrigerator's compressor may run more frequently and for longer periods, which can consume more energy and increase wear and tear on the appliance.

To maintain the optimal performance of your refrigerator, it's important to regularly defrost the freezer to prevent excessive ice buildup. Modern refrigerators often have automatic defrost cycles, but manual defrosting may still be required from time to time, especially if you notice ice accumulating. Proper maintenance helps ensure your refrigerator operates efficiently and keeps your food at the desired temperature.



7. The gas used in immersion tubes for lighting decoration and advertisement is-

a) Carbon dioxide

b) Ammonia

c) Sulfur dioxide

d) Neon


Answer. d) Neon;

The gas commonly used in immersion tubes for lighting decoration and advertisement, such as neon signs, is neon gas. Neon gas emits a bright and colorful glow when an electrical current passes through it, making it popular for creating eye-catching signs and displays. Other gases like argon and krypton can also be used in combination with phosphor coatings to produce different colors, but neon is the most iconic for its vibrant red-orange glow.



8. Expansion during heating

a) Occurs only in solid

b) Increase the weight of the material

c) Decrease the density of the material

d) Occurs at the same rate for all liquids and solids


Answer. c) Decrease the density of the material


9. When ice melts, then

a) Volume increase

b) Volume decrease

c) Mass increase

d) Mass decrease


Answer. b) Volume decrease


10. Thermostat is related to

a) Humidity

b) Temperature

c) Air

d) Clouds


Answer. b) Temperature;

A thermostat is related to temperature control in various heating and cooling systems. It is a device that monitors and regulates the temperature of a space or a system to maintain it within a desired range. Thermostats are commonly used in heating systems (e.g., furnaces) and cooling systems (e.g., air conditioners) to ensure that the environment or equipment operates at a comfortable or set temperature level. They can be manually adjusted or programmable to automatically control temperature settings based on user preferences or schedules.



11.  In cold countries, alcohol is preferred to mercury as a thermometric liquid because

a) Alcohol has a lower freezing point

b) Alcohol is a better conductor of heat

c) Alcohol is cheaper than mercury

d) The world production of alcohol greater than that of mercury


Answer. a) Alcohol has a lower freezing point;

Alcohol has a lower freezing point than mercury. In cold climates, especially during winter, alcohol-based thermometers are less likely to freeze and become unusable. Mercury thermometers can freeze in extremely cold conditions.



12. What is the function of the thermostat of a refrigerator?

a) to lower the temperature

b) To increase the freezing point 

c) To maintain a constant temperature

d) To decrease the melting point


Answer. c) To maintain a constant temperature;

The thermostat in a refrigerator serves a crucial function in maintaining the desired temperature inside the fridge and freezer compartments. Its primary role is temperature regulation


13. At what temperature are the readings of a Centigrade and Fahrenheit the same?

a) -40

b) 212

c) 40

d) 100


Answer. a) -40;

The temperature at which the readings of Celsius (Centigrade) and Fahrenheit are the same is approximately -40 degrees. So, -40 degrees Celsius and -40 degrees Fahrenheit are equal. This is a unique point of intersection between the Celsius and Fahrenheit temperature scales.


14. The normal temperature of the human body is 98.4 degrees F. Its equivalent temperature at 0 degree C is -

a) 40.16

b) 36.89

c) 35.72

d) 32.36


Answer. b) 36.89;

To convert a temperature from Celsius (Centigrade) to Fahrenheit, you can use the following formula:

°F = (°C × 9/5) + 32

Simply multiply the temperature in degrees Celsius by 9/5 (which is 1.8) and then add 32 to the result to get the temperature in degrees Fahrenheit.



15. When a glass rod is placed in steam, its length increases but its width-

a) Remains unchanged

b) Decrease

c) Increase

d) Becomes irregular


Answer. c) Increase


16. Which of the following statements is not true?

a) Air conditioner and Air cooler both maintain temperature

b) Air conditioner and Air cooler both maintain humidity

c) The air conditioner maintains humidity but the Air cooler does not maintain humidity

d) Both control the motion of the air


Answer. b) Air conditioner and Air cooler both maintain humidity;

Air conditioners and air coolers (also known as evaporative coolers) use different technologies to cool the air. Here are the primary technological differences between them:

Cooling Method:

Air Conditioner: Air conditioners use a refrigeration cycle to cool the air. They circulate refrigerant chemicals between an indoor and an outdoor unit, removing heat from the indoor air and releasing it outside. This process lowers both the temperature and humidity of the air inside the room.

Air Cooler: Air coolers work by evaporating water. They have a water reservoir and a fan. The fan draws in warm air, passes it through water-saturated pads or filters, and then expels the cooled and humidified air into the room.

Energy Efficiency:

Air Conditioner: Air conditioners are generally less energy-efficient than air coolers. The refrigeration process requires a lot of energy, making air conditioners costlier to operate in terms of electricity usage.

Air Cooler: Air coolers are more energy-efficient because they primarily use the energy to power the fan and water pump. They are often a more economical choice for cooling, especially in areas with low humidity.

Humidity Levels:

Air Conditioner: Air conditioners tend to reduce humidity levels in the room as they cool, which can be beneficial in humid climates.

Air Cooler: Air coolers add moisture to the air as they cool, making them suitable for dry or arid climates. However, they may not be ideal in humid conditions.

Installation:

Air Conditioner: Installation of air conditioners usually requires a more complex process, including mounting the outdoor unit and connecting refrigerant lines. Professional installation is often recommended.

Air Cooler: Air coolers are relatively easy to set up and can be used in most locations without special installation requirements.


Environmental Impact:

Air Conditioner: Air conditioners may use refrigerants that can be harmful to the environment if they leak. Proper maintenance and responsible disposal are essential to mitigate these environmental concerns.

Air Cooler: Air coolers are considered more environmentally friendly as they do not use harmful refrigerants and consume less electricity.



17. What does an air conditioner installed in a room control?

a) temperature only

b) Humidity and temperature only

c) Pressure and Temperature only

d) Humidity, pressure, and temperature 


Answer. b) Humidity and temperature only


18. In which of the following conditions will wet clothes dry the most quickly?

a) 100 % humidity, 60 degree Centigrade temperature  

b) 100 % humidity, 20 degrees Centigrade temperature  

c) 20 % humidity, 20 degrees Centigrade temperature  

d) 20 % humidity, 60 degree Centigrade temperature  


Answer. d) 20 % humidity, 60 degree Centigrade temperature  


19. On adding common salt to water, the boiling point and freezing point of water will-

a) Increase

b) Decrease

c) Decrease and Increase respectively

d) Increase and decrease respectively


Answer. d) Increase and decrease respectively


20. It is more comfortable to wear white clothes in summer because-

a) They reflect all the heat falling on them

b) They radiate heat transferred from the body

c) They absorb perspiration

d) They are soothing to the eye


Answer. a) They reflect all the heat falling on them;

Wearing white clothes in summer is more comfortable because white fabrics reflect more sunlight and heat than dark-colored fabrics.

Reflectivity: White clothing reflects a significant portion of the sunlight that hits it. This reflection means that less heat is absorbed by the fabric and, consequently, less heat is transferred to your body. Dark-colored clothing, on the other hand, absorbs more heat, making you feel warmer.

Heat Absorption: Dark colors, such as black, navy, or dark red, absorb a wider spectrum of light, including infrared radiation. This absorption of heat energy can increase your body temperature and make you feel hotter.


21. Consider the following statements-

Assertion A: Light-colored clothes are preferred in summer.

Reason R: Light colors are poor absorbers of heat.

Select the correct answer from the code given below-

a) Both A and R are true, and R correctly explains A.

b) Both A and R are true but R does not correctly explain A

c) A is true but R is false

d) A is false but R is true


Answer. a) Both A and R are true, and R correctly explains A.


22. In an earthen pitcher, the water remains cold due to the process of-

a) Condensation

b) Evaporation

c) Sublimation

d) None of the above


Answer. b) Evaporation;

Water remains cold in an earthen pitcher due to a process called evaporative cooling. Here's how it works:

Porosity of Earthenware: Earthen pitchers are typically made from porous clay or terracotta. These materials have tiny pores or small openings that allow air and moisture to pass through them.

Water Seepage: When you fill an earthen pitcher with water, some of the water is absorbed by the porous walls of the pitcher.

Evaporation: As the water on the outer surface of the pitcher evaporates, it absorbs heat from the surrounding environment. This process is called evaporative cooling.

Heat Transfer: When water molecules evaporate, they take away heat energy from the pitcher's surface and the water inside. This heat transfer cools down the contents of the pitcher.

Cooling Effect: The constant evaporation and heat absorption keeps the water inside the pitcher at a lower temperature than the surrounding air, resulting in a refreshing and cool drink.



23. Humid heat is experienced in summer when the weather-

a) It is unfortunate

b) It is intense

c) it is scorching

d) It is humid


Answer. d) It is humid


24. Xeric condition refers to

a) Low temperature

b) Low humidity

c) High evaporation

d) Extreme temperature


Answer. b) Low humidity;

Xeric conditions refer to environments or regions characterized by a scarcity of water or low moisture availability. These conditions are typically dry, arid, or desert-like, where water is limited, and there is often a lack of consistent rainfall. Xeric environments are known for their harsh and challenging conditions for plant and animal life, and they often require specialized adaptations for survival.


The term "xeric" is derived from the Greek word "xēros," which means "dry." Xeric conditions can be found in various parts of the world, including deserts, semi-arid regions, and certain coastal areas with limited freshwater sources. 



25. Assertion A- Woollen clothes keep us warm

Reason R- Woolen fibers are made from a special type of protein, which is a bad conductor of heat.

Select the correct answer from the codes given below-

a) Both A and R are true, and R is the correct explanation of A.

b) Both A and R are true, but R is not the correct explanation of A

c) A is true but R is false

d) A is false but R is true


Answer. a) Both A and R are true, and R is the correct explanation of A.


26. The maximum density of water is at

a) At 373 Kelvin

b) At 277 Kelvin

c) At 273 Kelvin

d) At 269 Kelvin


Answer. b) At 277 Kelvin;

To convert a temperature from Kelvin to degrees Celsius, you can use the following formula:

°C = K - 273.15

Simply subtract 273.15 from the temperature in Kelvin to get the temperature in degrees Celsius.



27. Why does water boil at temperatures below 100 centigrade at higher altitudes?

a) The atmospheric pressure decreases and hence boiling point is lowered

b) The gravitational attraction is less

c) Because of heavy winds in the mountains

d) None of the above is correct


Answer. a) The atmospheric pressure decreases and hence boiling point is lowered


28. If an unsaturated sugar solution is prepared by mixing 100 grams of sugar in half a liter of water, which of the following physical amounts will not change?

a) The mass

b) The density

c) Concentrations

d) Volume


Answer. d) Volume


29. The safest temperature for keeping food fresh in a refrigerator is

a) 4 degrees C

b) 8 degrees C

c) 0 degrees C

d) 10 degrees C

release

Answer. a) 4 degrees C


29. When soggy biscuits are kept inside the fridge for some time they become crisp because-

a) Cooling releases extra moisture

b) Humidity inside the fridge is low and extra moisture is absorbed

c) Humidity inside the fridge is high and extra moisture is absorbed

d) Pressure inside the fridge is high and helps in releasing extra moisture


Answer. b) Humidity inside the fridge is low and extra moisture is absorbed



30. In Cold Weather, aquatic animals survive even when water at the top layer of the lake freezes into ice because-

a) They can breathe in ice

b) They have enough accumulated oxygen inside them

c) Their body structure is such that the survive without oxygen

d) Water has the highest density at 4 degrees centigrade so underneath the top layer of ice there is a layer of water.


Answer. d) Water has the highest density at 4 degrees centigrade so underneath the top layer of ice there is a layer of water.


31. Fish can survive in a frozen lake because-

a) Fish are warm-blooded animals

b) Fish hibernate in ice

c) Water does not freeze at the bottom of the lake

d) Ice is a good conductor of heat


Answer. c) Water does not freeze at the bottom of the lake


 32. Why do pendulum clocks usually lose time in summer?

a) Due to longer days in summer

b) Due to friction caused by coils

c) The length of the pendulum increase

d) The weight of the pendulum change in summer


Answer. c) The length of the pendulum increase;

Pendulum clocks can lose time in summer due to changes in temperature. Here's why this happens:

Expansion and Contraction: The pendulum in a pendulum clock is typically made of a metal rod, such as steel. Metals expand when they are heated and contract when they are cooled. As the temperature rises in the summer, the metal pendulum rod will expand, causing it to become slightly longer.

Effect on Pendulum Length: The length of the pendulum is a critical factor in determining the clock's period (the time it takes for one complete swing). When the pendulum becomes longer due to expansion from the heat, its period increases slightly. This means that each swing of the pendulum takes a fraction of a second longer than it would at a cooler temperature.

Timekeeping Accuracy: Pendulum clocks rely on the regular and precise swings of the pendulum to keep time accurate. When the pendulum's length changes with temperature fluctuations, it can lead to a minor change in the clock's timekeeping rate. In the case of expansion in hot weather, the clock will run slightly slower, causing it to lose time.

Regulation: Some pendulum clocks have a mechanism for adjusting the length of the pendulum to compensate for temperature changes. However, not all pendulum clocks have this feature, and even those that do may require periodic adjustments to maintain accurate timekeeping.


33. The hand burns more by steam comparatively to boiling water, because- 

a) The steam has a latent heat

b) Steam sneaked into the body

c) The steam has more power

d) Steam is the gig


Answer. a) The steam has a latent heat;

Hands can burn more severely from contact with steam compared to boiling water because of differences in temperature and the transfer of heat energy. Here's why steam can be more damaging:

Temperature Difference: Steam is typically hotter than boiling water. While the temperature of boiling water is 100 degrees Celsius (212 degrees Fahrenheit) at standard atmospheric pressure, steam can be significantly hotter, depending on the pressure. Steam can reach temperatures well above 100 degrees Celsius. The higher the temperature, the more heat energy it contains.

Heat Transfer: When you touch boiling water, heat is transferred from the water to your skin through conduction. While this can still cause burns, it's relatively less efficient compared to steam.

Phase Change: Steam undergoes a phase change from a gas to a liquid when it comes into contact with a cooler surface, such as your skin. During this phase change, it releases a significant amount of heat energy, known as latent heat of vaporization. This additional heat energy transfer can cause more severe burns.

Heat Capacity: Steam has a higher heat capacity than boiling water, which means it can transfer more heat energy to your skin over a shorter period, causing more rapid and severe burns.



34.


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