# Temperature

Andrew is having a fever, he went to the doctor for treatment.

The doctor measures his body temperature.

His body temperature was 102-degree Fahrenheit.

He asked his father, what does 'temperature' mean?

His father told him that it is a measure of the hotness and coldness of a body.

We also learn about temperature vs heat.

Check-out the interactive simulation to know more about the lesson and try your hand at solving a few interesting practice questions on independent events at the end of the page.

## Lesson Plan

 1 What Is Temperature? 2 Important Notes on Temperature 3 Solved Examples on Temperature 4 Challenging Questions on Temperature 5 Interactive Questions on Temperature

## What Is Temperature?

The definition of temperature says that it is a measure of the hotness and coldness of a body. It is not easy to give an exact definition of temperature. Based on our physiological sensations, we can express the level of temperature qualitatively with words like hot, cold, warm, etc.

Temperature is simply an average measure of the kinetic energy for particles of matter, the more is their kinetic energy, the higher the temperature of the body/object.

## Measurement of Temperature

Temperature Measurement: Measurement of temperature describes the process of measuring the temperature of an object or a body.

The temperature is measured with thermometers that may be calibrated to a variety of temperature scales because the temperature is a relative measurement. For accurate measurement of temperature, scales based on reference points must be used.

There are three main scales commonly used to measure the temperature:

1.  The Fahrenheit scale, whose symbol is (°F).
2. The Celsius scale, whose symbol is (°C).
3. The Kelvin scale, whose symbol is (K).

Each of these scales has different reference points and uses a different set of divisions based on them.

The Celsius scale is generally used for most temperature measuring purposes.

## How Does a Thermometer Measure the Temperature?

There are several materials whose properties change with the temperature in a repeatable and predictable manner and this forms a way for accurate temperature measurement.

The glass thermometer is one of the most common devices for measuring temperature.

The glass thermometer is a glass tube filled with mercury or some other liquid, in which mercury acts as the working fluid.

Temperature increase causes the fluid to expand, mercury changes its property with respect to the temperature as the temperature increases the volume of mercury also increases.

So the temperature can be determined by measuring the volume of the fluid and temperature can be read simply by observing the level of the fluid in the thermometer.

Generally, we use a mercury-in-glass thermometer.

Similarly, there are a few other instruments that are used for the measurement of temperature:

• Thermocouples
• Thermistors
• Infrared thermometer
• Resistance temperature detector (RTD)
• Pyrometer
• Langmuir probes (for measuring electron temperature of a plasma)

## Temperature vs Heat

In thermodynamics, heat and temperature are closely related concepts with precise definitions. Heat should not be confused with temperature but they can directly be related. Few relations between temperature and heat are given below:

Temperature Heat
Temperature is the measure of a degree of hotness or coldness. Heat is the transfer of thermal energy between molecules and is measured in Joules.
Temperature describes the average kinetic energy of molecules. Heat measures how energy moves or flows.
SI unit is Kelvin SI unit is Joule
The unit of Temperature: Fahrenheit $$^\circ\textF$$, Celsius $$^\circ\textC$$, Kelvin $$\text K$$  The unit of heat: Joules $$\text (J)$$ and Calories $$\text (Cal)$$

The symbol of temperature is "T"

The symbol of heat is "Q"

## Temperature Scales

Temperature scales measure the hotness and coldness of a body,
The three temperature scales are Celsius, Fahrenheit, and Kelvin.

According to the Kelvin scale, the freezing and the boiling point of water are 273.15K and 373.15K respectively.
According to the Fahrenheit scale, the freezing and the boiling point of water are 32°F and 212°F respectively.
According to the Celsius scale, the freezing and the boiling point of water are 0°C and 100°C respectively.

## Temperature Scales Conversion

Using conversion formulas, temperatures can be converted from one scale to another.

In temperature conversion the value of temperature changes from one unit to another.

The three main conversions of temperature:
•  Between Celsius and Kelvin.
•  Between Fahrenheit and Kelvin.
•  Between Celsius and Fahrenheit.

Conversion Formulas are given below in the table:

Conversion of Temperature
From
Formulas
Celsius to Kelvin  $$\text{ K = C }+ 273.15$$
Kelvin to Celcius $$\text {C = K }− 273.15$$
Fahrenheit to Celsius  $$\text {C = (F} - 32) \dfrac59$$
Celsius to Fahrenheit $$\text {F = C} \dfrac95 + 32$$
Fahrenheit to Kelvin  $$\text{ K = (F} - 32) \dfrac59 + 273.15$$
Kelvin to Fahrenheit  $$\text {F = (K} - 273.15 ) \dfrac59 +32$$

Important Notes
• Temperature is simply an average measure of the kinetic energy for particles of matter.
• The Celsius scale is generally used for most temperature measuring purposes.
• The Fahrenheit (°F) temperature scale is used in the United States.

## Solved Examples

 Example 1

Jason wants to know, what instrument is used to measure the average kinetic energy of a body or substance?

Solution

A thermometer is an instrument that is used to measure the average kinetic energy of a body or substance.

 $$\therefore$$ Thermometer is used to measure temperature.
 Example 2

Noah knows that one-degree Celsius is equal to 273.15 Kelvin. He wants to calculate 30°C in Kelvin. How much is 30°C in Kelvin?

Solution

Given,

One-degree Celsius is equal to 273.15 Kelvin.

From the temperature conversion formula, we can convert Celsius to Kelvin

that is, K = C + 273.15

Putting the value:

$\text K = 30 + 273.15 \text K = 303.15 \text K$

 $$\therefore$$ 30°C in Kelvin is 303.15 K
 Example 3

Isabella knows the body temperature is generally 37ºC. But she wants to know what is the body temperature in Fahrenheit? Can you help her?

Solution

Given,

The body temperature on the Celcius scale is 37ºC.

Using the formula of conversion from Celsius to Fahrenheit is $\text {F = C} \dfrac95 + 32$

On putting the value, we get $\text F=37^\circ \text C \times \dfrac {9}{5} + 32 \text F = 98.6$

 $$\therefore$$ The body temperature in Fahrenheit is 98.6
 Example 4

Joseph knows that the freezing point of water on the kelvin scale is 273.15K. He wants to know the freezing point of water on the Fahrenheit scale. Can you help him find the answer?

Solution

Given,

The freezing point of water on the Kelvin scale is 273.15K.

So, the freezing point of water on the Fahrenheit scale is 32°F.

 $$\therefore$$ The freezing point of water on the Fahrenheit scale is 32°F.

Challenging Questions
• What is a Rankine scale?

• What is latent heat?

• What is the thermal equilibrium condition?

## Interactive Questions

Here are a few activities for you to practice. Select/Type your answer and click the "Check Answer" button to see the result.

## Let's Summarize

Mini-lesson targeted the fascinating concept of temperature. The math journey around the temperature starts with what a student already knows, and goes on to creatively crafting a fresh concept in the young minds. Done in a way that not only it is relatable and easy to grasp, but also will stay with them forever. Here lies the magic with Cuemath.

At Cuemath, our team of math experts is dedicated to making learning fun for our favorite readers, the students!

Through an interactive and engaging learning-teaching-learning approach, the teachers explore all angles of a topic.

Be it worksheets, online classes, doubt sessions, or any other form of relation, it’s the logical thinking and smart learning approach that we, at Cuemath, believe in.

## 1. What does temperature measure?

Temperature measures the hotness and coldness of a body.

## 2. What is the temperature?

Temperature is a physical quantity that expresses the hotness and coldness of a body.

## 3. Which temperature scales have no negative values?

Kelvin scale has no negative values.

## 4. Which temperature scale is the most commonly used?

Fahrenheit scale is the scale most commonly used.

## 5. Which temperature scale is most commonly used for scientific researches?

Kelvin scale is most commonly used for scientific researches.

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