Temperature and its Measurement | Science Grade 6 CBSE

Play with it

The six ideas of temperature

Hotness is one idea, but it has many parts — what it is, how we measure it, and how to do it safely. Tap each term to see what it means.

Explore · Temperaturetap a term

Learn

The three big ideas

Hot and cold are relative. Take three bowls – warm, lukewarm and chilled water. Hold one hand in the warm and one in the chilled water for a minute, then dip both into the lukewarm bowl. The same water feels cold to one hand and warm to the other. Touch cannot give a reliable value.
Temperature is the quantity that tells us, with a number, how hot or cold a body is.
Heat flows from hot to cold. Hot milk left on the table slowly cools until it reaches the room’s temperature – warmth always moves from the hotter object to the cooler one until both match.
Heat and temperature are linked but not the same: heat is the energy that flows; temperature is the reading that tells how hot the body is.

A thermometer is a thin glass tube with a bulb of liquid. As it warms, the liquid expands and rises up the fine tube against a marked scale. Older ones used mercury; safer modern ones use a coloured spirit or a digital sensor.
Clinical thermometer – for body temperature. Range about 35°C to 42°C. It has a tiny bend (a kink) that stops the liquid slipping back, so the reading holds after you remove it; shake it down before reusing.
Laboratory thermometer – a wide range, about −10°C to 110°C, with no kink, so you read it while it is still in place.
Digital thermometer – a sensor shows the number on a screen and beeps when done. It is the safest, with no mercury to break.

Worked example. A student dips a laboratory thermometer first in melting ice, then in boiling water at sea level. What two readings should appear?

Melting ice → 0°C. Boiling water → 100°C. These are the two fixed points of the Celsius scale.

Common mistake: using a clinical thermometer to measure hot water. Its scale stops near 42°C; the rising liquid has nowhere to go and the glass can crack. Use a laboratory thermometer for anything hotter than the body.

Celsius (°C) – the everyday scale. Two fixed points set it: 0°C where ice melts and 100°C where water boils (at sea level); the gap is divided into 100 equal degrees.
Fahrenheit (°F) – an older scale: water freezes at 32°F, boils at 212°F, and the body sits near 98.6°F.
Kelvin (K) – the scientists’ SI unit. It starts at the coldest possible temperature (0 K, called absolute zero); 0°C equals 273 K.
Safe habits: hold a thermometer by its stem, not the bulb; clean it with an antiseptic before and after use; read it at eye level; wait a few minutes after a hot or cold drink before taking a mouth reading; if a mercury thermometer breaks, do not touch the silver beads (mercury is poisonous) – tell an adult.

Where you'll meet it

Temperature in everyday life

Spotting a fever

When you feel unwell, a clinical or digital thermometer turns "I feel hot" into a number. A reading clearly above 37°C tells a parent or doctor there is a fever – a fact, not a guess.

The cold chain

Vaccines and milk must stay cold from the factory to the village. Workers check chillers and ice-boxes with thermometers – milk below about 4°C, many vaccines between 2°C and 8°C – so nothing spoils on the way.

Weather & cooking

The daily forecast that says "Delhi 44°C" and the oven dial that bakes bread at the right heat both rely on temperature measurement – the same idea, from a heat wave to a kitchen.

Check yourself

Competency quiz

Modelled on the competency-based pattern — MCQ, assertion–reason and a case study, testing whether you can use the ideas, not just recall them.

Score 0/12