Temperature for Class 5

In this chapter, we will deal with the concept of temperature and understand its impact on our daily lives. Temperature serves as a fundamental concept that enables us to determine the degree of warmth or coldness in our surroundings. We witness temperature variations throughout the changing seasons.

What is Temperature?

Temperature is a measure of how warm or cool something is. We experience a large number of items that can be sorted as either hot or cold. Temperature is represented by the letter 'T'.

Objects with a high temperature are hot objects like a bulb, a steaming cup of coffee, a thundering fire, the searing sun, etc.

On the other hand, objects with a low temperature are cold objects like ice cubes, snow, frozen yogurt, etc.

We feel warm in the summer season and cold in the winter season.

Temperature Measuring Instruments:

A temperature measuring instrument is a thermometer that serves as a tool employed for temperature measurement which comprises a sealed glass tube with a narrow bore that contains a liquid as mercury.

Modern thermometers use digital technology for temperature measurement. Digital thermometers which don't contain mercury are mostly used in hospitals and clinics.

Temperature Measurement Units

Temperature can be expressed using the following units:

→ Celsius (°C) 
→ Fahrenheit (°F)
→ Kelvin (K)

The degree (°) is used in temperature measurement to represent degrees on various temperature scales in Celsius (°C) and Fahrenheit (°F).

Conversion of Units of Temperature:

Formulae for converting temperature from one unit to another are as follows:

Celsius to Fahrenheit:

→ [°F] = [°C] × 9/5 + 32

OR 

→ [°F] = [°C] × 1.8 + 32

Fahrenheit to Celsius:

[°C] = 5/9 × [(°F) − 32]

Celsius to Kelvin:

→ [K] = [°C] + 273.15

Kelvin to Celsius:

→ [°C] = [K] − 273.15

These conversions allow you to change temperature values between Celsius, Fahrenheit and Kelvin units.

Let us solve some examples to understand them better.

Example 1: What is the room temperature in Kelvin if the room temperature is 38.47°C less than the temperature shown on the thermometer?

a) 28 K
b) 304.48 K
c) 304.68 K
d) 304.88 K

Answer: c) 304.68 K

Explanation: Temperature shown on the thermometer = 70°C

Room temperature is 38.47°C less than the temperature shown on the thermometer.

Room temperature = 70°C − 38.47°C
                                = 31.53°C

Using [K] = [°C] + 273.15

Room temperature in Kelvin = 31.53°C + 273.15
                                                = 304.68 K

Example 2:  The temperature in the hall was 93.45°F this evening. After three hours, it had gone up by 28.2°F and then the temperature fell by 35.65°F after four hours. What was the temperature in °C after seven hours?

a) 27°C
b) 30°C
c) 54°C
d) 60°C

Answer: b) 30°C

Explanation: Temperature after 7 hours = (93.45 + 28.2 – 35.65)°F
                                                               = 86°F

Using [°C] = 5/9 × [(°F) - 32)]

Temperature in °C after 7 hours = 5/9 × [(86°F) - 32]
                                               = 5/9 × 54
                                               = 30°C