A clinical thermometer is a specialized medical device designed to accurately measure the human body temperature. It is a crucial tool for diagnosing fevers and monitoring health conditions.

It operates on the principle of thermal expansion. Traditionally, it contained a narrow, sealed glass tube with a bulb at one end filled with mercury. When placed in the mouth, armpit, or rectum, the heat from the body causes the mercury to expand, forcing it to rise up the narrow constriction (kink) in the tube. This kink prevents the mercury from falling back immediately after removal, allowing for a reading to be taken.

The scale is marked from 35°C (95°F) to 42°C (107.6°F). This limited range covers all possible variations in human body temperature, which normally hovers around 37°C (98.6°F). The scale is finely divided into 0.1°C or 0.2°F divisions for high precision.

• Diagnosing Fever: The primary use is to check for an elevated body temperature, a key symptom of infection and illness.
• Monitoring Health: Tracking the progress of a fever (e.g., to see if medication is working).
• Preventive Healthcare: Routine check-ups to ensure normal body function.
• Hospitals and Homes: Used extensively by medical professionals and for personal home care.

A laboratory thermometer is a device designed for scientific experiments to measure temperature with a high degree of precision. It is used for a wide range of substances, not just the human body.

Traditional laboratory thermometers operate on the principle of thermal expansion, similar to clinical thermometers. A liquid (historically mercury or now often a safe organic red liquid) is sealed in a glass tube with a bulb at the end. When heated, the liquid expands and rises up the narrow capillary tube to indicate the temperature. Unlike clinical thermometers, they do not have a constriction (kink), so the level falls once removed from the heat source. Modern versions may be digital, using a thermistor probe for electronic measurement.

The scale is a key differentiating feature. It has a much wider range than a clinical thermometer, typically from -10°C to 110°C or even broader (e.g., -200°C to over 500°C for specialized types). This allows it to measure the boiling and freezing points of various substances. The graduations are precise, often marked in whole degrees or 0.1° or 0.2° divisions for accuracy.

• Scientific Experiments: Measuring the temperature of chemicals, solvents, and mixtures during reactions in chemistry and biology labs.
• Educational Use: Demonstrating principles of heat and thermodynamics in school and university science classes.
• Industrial Use: Monitoring temperatures in manufacturing and quality control processes.
• Meteorology: Used in weather stations to measure ambient air temperature (often in a Stevenson screen).

A digital thermometer is a modern electronic device used to measure temperature. It has largely replaced traditional mercury thermometers due to its safety, speed, and ease of reading.

It operates using a thermistor, a type of electrical resistor whose resistance changes predictably with temperature. The thermometer's probe is placed at the measurement site. The internal microprocessor detects the change in resistance, converts it into a temperature value, and displays it digitally on a liquid crystal display (LCD) screen. Most models signal the end of the measurement with an audible beep.

Digital thermometers are highly versatile and can be programmed to display temperature in Celsius (°C) or Fahrenheit (°F). Their electronic range is typically broader than a clinical thermometer, often from about 32°C (90°F) to 43°C (110°F) or wider, making them suitable for various applications beyond just human body temperature.

• Medical Use: Measuring human body temperature orally, rectally, or axillarily (underarm). Some designs are specifically for tympanic (ear) or temporal (forehead) use.
• Domestic Use: A common household item for checking for fever in adults and children. Their unbreakable design and lack of glass or mercury make them safe for home use.
• Culinary Use: Certain models are used to measure the temperature of food, liquids, or cooking surfaces.
• Aquarium and Laboratory Use: Their quick response and digital accuracy make them useful for monitoring environmental temperatures.

The Maximum and Minimum thermometer is a specialized instrument designed to record the highest and lowest temperatures reached over a specific period, usually 24 hours. It is invaluable in meteorology, horticulture, and agriculture for tracking temperature fluctuations.

It operates on the principle of thermal expansion of a liquid and the physical displacement of indicators. Unlike a standard thermometer that shows the current temperature, this thermometer has two separate indicators that are pushed by the expanding fluid and remain at their extreme positions until manually reset.

• Meteorology and Weather Stations: Its primary use is in weather forecasting and climate recording. It provides crucial data on daily and nightly temperature ranges.
• Agriculture and Horticulture: Farmers and gardeners use it to monitor conditions critical for plant growth, to predict frosts, and to protect sensitive crops.
• Greenhouse Management: Essential for maintaining optimal and stable temperature ranges for plants inside a greenhouse.
• Educational Purposes: Used in schools to teach students about weather patterns, temperature extremes, and the properties of thermal expansion.

An Infrared (IR) thermometer, also known as a pyrometer or non-contact thermometer, is a device that measures the temperature of a surface from a distance by detecting the infrared radiation it emits. It is renowned for its speed, safety, and ability to measure objects that are difficult to access, moving, or extremely hot.

It operates on the fundamental principle of black body radiation. All objects with a temperature above absolute zero (-273.15°C) emit infrared radiation. The intensity and wavelength of this radiation are directly proportional to the object's temperature. The IR thermometer captures this radiation and converts it into an electrical signal, which is then translated into a temperature reading.

• Medical and Healthcare: Rapid, non-contact screening of body temperature (e.g., temporal artery or tympanic thermometers), minimizing cross-contamination.
• Industrial Maintenance: Identifying overheating electrical components (circuit breakers, connections), mechanical parts (bearings, motors), and steam traps to predict failures.
• Food Safety: Checking the surface temperature of food, grills, refrigerators, and storage areas without making contact, which is crucial for HACCP compliance.
• HVAC: Diagnosing issues with heating and air conditioning systems by measuring vent temperatures, coil performance, and insulation efficiency.
• Automotive: Checking tyre tread temperature, brake disc temperature, and engine performance.
• Scientific Research: Measuring temperatures in experiments where contact is impossible or would interfere with the process.

Mercury Thermometer

–39°C to 357°C

Alcohol Thermometer

–117°C to 78°C

In the cold region in winter season, the surrounding temperature falls to 0°C. When the surrounding temperature falls to 0°C, water inside the pipe changes to ice. The ice occupies more space but the pipe is contracted due to excessive cold. Thus a high pressure is created and pipe gets burst.

Due to anomalous expansion of water, water has maximum density at 4°C, which is equal to 1g/cm³. Hence density is measured at 4°C.

Due to anomalous expansion of water in cold region water at 4°C being heavier lies below the surface of the water hence this temperature prevents the liquid food from freezing.

Due to anomalous expansion of water when water is placed in a vessel, different layers of water is formed with 0°C, 1°C, 2°C, 3°C, 4°C from top to bottom. As 4°C has higher density so, water starts to freeze from top but for other liquids like ghee or wax they shows normal behavior. So, different layers with higher temperature and bottom contains 0°C liquid. So, liquid starts to freeze from bottom.

During too much cold condition, temperature falls below 4°C. So, water pressure inside fruits and vegetables expands may burst and other components may be damaged due to expansion of water inside them.

Soft drink bottles must be kept in freezing chamber of refrigerator for cooling purpose. During this the water present in Soft drink expands on cooling from 4°C to 0°C and occupies the empty space. This prevent the bottles from bursting. Therefore, soft drink bottles are not completely filled to prevent them from bursting while cooling in refrigerator.

In winter season, the atmospheric temperature falls below our normal body temperature (37°C). Due to this difference in temperature heat energy starts to flow from body to the surrounding. So, our body cools. So, to prevent our body from excessive cooling, we need warm clothes in winter.

Similar to the anomalous expansion of water metal antimony also expands on cooling and contracts at first when heated above the melting point.

In summer season, atmospheric temperature goes up higher than our normal body temperature (37°C) so, heat energy starts to flow from surroundings to our body. So, to maintain constant temperature body starts to lose temperature in the form of sweat.

The kinetic energy of the vibrating solid increases when a solid is heated because the molecule gets extra heat energy for vibration. Due to this, the intermolecular force of attraction between the molecules decreases. When the solid is further heated, the solid starts melting due to vey weak intermolecular attraction.

A new quilt is thicker than the old one. The thicker quilt contains more spaces which get filled with more air as compared to that of the old quilt. Since air is bad conductor of heat, it does not allow the flow of heat from the body. As a result, a new quilt is felt warmer than the old one.

A glass is filled with certain liquid at certain temperature such that it overflows either heated or cooled. The liquid is water at 4°C. It is because; water is a liquid which shows anomalous behavior in expansion. When water is heated from 0°C to 4°C, it contracts instead of expanding and when it is further heated beyond 4°C, it expands. Water has highest density at 4°C. Therefore, the given liquid is water at 4°C.

Water will overflow from both of the beakers because due to anomalous expansion of water, water has high density and least volume at 4°C, when it is heated it expands according to the normal expansion of water whereas when it is cooled it's volume increases due to anomalous expansion of water.

The temperature of anybody depends upon the average K.E. of the molecules and is independent of the no. of molecules but heat energy depends upon the no. of molecules and K.E. of each molecule. So, according to the different mass the heat energy may be different in the bodies having same temperature.

When boiling water is kept in a glass tumbler, the lower part of the glass is heated so expands but since glass is insulator of heat, the upper part can't expands so it may leads to the cracking of glass.

Since the temperature of water is greater than ice the vibration of the molecules of the water is greater than the vibration of the molecules of the ice.

Mercury will have high temperature because its specific heat capacity is low.

The specific heat capacity of water is 4200 J/kg°C which is too much high. Water absorbs large amount of heat energy from the engine with less rise in temperature. So, water is used as a coolant in the radiator of the vehicle to cool engine.

Hot water bag is used to heat the swollen part of the body for longer time. Since, specific heat capacity of water is high, the water remains hot for longer time. So, it is used in a hot water bag.

When a person is suffering from fever, a wet handkerchief is kept on forehead to lower his body temperature because the wet handkerchief contains water, whose specific heat capacity is high, absorbs large amount of heat energy with less rise in temperature of the water. So, it helps to reduce the temperature of the patients.

The specific heat capacity of water (4200 J/kg°C) is much more greater than the specific heat capacity of sand (800 J/kg°C). So, to the same rise of temperature water needs almost 5 times more heat energy than sand. So, sandy soil gets heated very quickly as compared to wet soil.

The specific heat capacity of soil (land surface) is much more less than that of the water. So, during winter night, the temperature of the soil decreases very fast than the water. As a result in the morning times heat from water starts to move from the well water. Hence, well water is felt warmer in the morning during winter season.

The surface of desert contains large amount of sand having specific heat capacity low(800 J/kg°C). So, due to less specific heat capacity sand becomes very hot during day by getting heat of the sun whereas the hot sand also looses it's heat very soon during night. So, in deserts, days are very hot and the nights are very cold.

Sea and ocean consists of a large amount of water having specific heat capacity high(4200 J/kg°C). Due to this it gets heated slowly during day and gets cooled very slowly during night. Therefore, the difference in temperature is very low near sea because of land breeze and sea breeze.

The specific heat capacity of steel is less than wood. So, the steel chair looses heat energy fast and becomes cold faster than the wooden chair. So, we feel more cold in a steel chair than wooden chair during winter.

The blowing of air towards the land from the sea is called land breeze whereas the blowing of air towards the sea from land is called sea breeze.

The specific heat capacity of water is much greater than the sand. So, in the day time due to the sunlight, the temperature of the sand increases rapidly but the temperature of water near the sea increases slowly. So, the air starts to blow from sea to the land which is called sea breeze whereas during night, the temperature of water falls slowly and the temperature of sand falls rapidly causing the flow of air from land towards the sea, this is called land breeze.

The earthen pot contains different capillary pores. So, from these pores water comes out due to evaporation. The evaporating water takes heat from the water inside the pot. So, the water in the pot remains cooled.

Solution:

According to the relation of the temperature scale:

(C - 0)/100 = (F - 32)/180

Or, (40 - 0)/100 = (F - 32)/180

Or, 720 = 10F - 320

Or, 10F = 1040

Or, F = 104

Hence, 40°C = 104°F

Solution:

We have, 1 cal/g°C = 4200 J/kg°C

Or, 2.356 cal/g°C = 4200 × 2.356 J/kg°C

= 9895.2 J/kg°C

Hence, 2.356 Cal/g°C = 9895.2 J/kg°C

Solution:

Mass of water (m) = 20kg

Specific heat capacity (S) = 4200 J/kg°C

Initial temperature (t₁) = 30°C

Final temperature (t₂) = 100°C

Difference in temperature (Δt) = t₂ - t₁ = 100 - 30 = 70°C

Heat energy (Q) = ?

We have, Q = mSΔt

Or, Q = 20 × 4200 × 70

Or, Q = 5.88 × 10⁶ J

Hence, 5.88 × 10⁶ Joule of heat energy is absorbed by the water.

Solution:

Let the final temperature of mixture be 'T'

From principle of calorimetry:

Heat lost by hot water = Heat gained by cold water

Or, Q₁ = Q₂

or, m₁s(t₁ - T) = m₂s(T - t₂)

or, 5 × (80 - T) = 10 × (T - 50)

or, 80 - T = 2T - 100

or, 180 = 3T

or, T = 60°C

Hence, the final temperature of mixture is 60°C.

Solution:

Mass of water (m) = 50kg

Heat energy (Q) = 3.6 × 10⁶ J

Rise in temperature (Δt) = ?

Specific heat capacity (s) = 4200 J/kg°C

We have, Q = msΔt

Or, 3.6 × 10⁶ J = 50 × 4200 × Δt

Or, Δt = 3.6 × 10⁶ / 210000

Or, Δt = 17.14°C

Hence, Rise in temperature = 17.14°C

Solution:

Mass of water (m) = 50kg

Specific heat capacity (s) = 4200 J/kg°C

Power of heater (P) = 1000 W

Time taken (t) = 1hr = 60 × 60 seconds = 3600 seconds

We have, Power = Heat energy (Q) / time taken

Or, Heat energy (Q) = P × t

Or, Q = 1000 × 3600

Or, Q = 3.6 × 10⁶ J

Again from heat equation Q = msΔt

Or, 3.6 × 10⁶ = 50 × 4200 × Δt

Or, Δt = 17.14°C

Hence, Rise in temperature = 17.14°C