Temperature is the degree of hotness of a body.
(a) Temperature of a normal human body is 98.6 °F. What is the corresponding temperature in the Celsius scale ?
(b) Define latent heat.
(c) Why a brass tumbler feels much colder than a wooden tray on a chilly day ?

Question

Accepted Answer

>

> [!TLDR]
> $98.6\,°F$ corresponds to $37\,°C$, the normal human body temperature. Latent heat is the heat needed to change the state of unit mass of a substance without changing its temperature. A brass tumbler feels colder than a wooden tray at the same temperature because brass is a much better conductor of heat and drains heat away from the skin faster than wood does.
>
> **(a) Converting $98.6\,°F$ to Celsius**
>
> The relation between the Fahrenheit scale and the Celsius scale is:
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> $\dfrac{C - 0}{100 - 0} = \dfrac{F - 32}{212 - 32}$, which simplifies to $C = \dfrac{5}{9}(F - 32)$
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> Substituting $F = 98.6$:
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> $C = \dfrac{5}{9}(98.6 - 32) = \dfrac{5}{9}	imes 66.6 = \dfrac{333}{9} = 37\,°C$
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> So the normal human body temperature, $98.6\,°F$, is $37\,°C$.
>
> **(b) Latent heat**
>
> Latent heat is the amount of heat energy required to change the state of a unit mass of a substance (e.g. solid to liquid, or liquid to vapour) at constant temperature, without producing any change in its temperature. If a mass $m$ of a substance undergoes a change of state, the heat exchanged is:
>
> $Q = mL$
>
> where $L$ is the specific latent heat of the substance for that particular change of state (e.g. latent heat of fusion for melting, latent heat of vaporisation for boiling). Since no temperature change occurs during the process, this heat goes entirely into changing the internal (potential) energy associated with the arrangement of molecules in the new state.
>
> **(c) Why brass feels colder than wood on a chilly day**
>
> On a chilly day, both the brass tumbler and the wooden tray are at the same temperature — the temperature of the room/surroundings, which is lower than the temperature of our hand.
> …

Scale	Freezing point of water	Boiling point of water	Used by
Celsius (°C)	0	100	Most of the world, science
Fahrenheit (°F)	32	212	USA, a few other countries
Kelvin (K)	273.15	373.15	All scientific work

Q.Temperature is the degree of hotness of a body.

Concept understanding — Temperature Scale Conversion

Temperature Scale Conversion

The core idea

The three main scales you'll meet

The conversion formulas

Why the formulas look like that

A worked example

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Q.Temperature is the degree of hotness of a body.

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