CLASS 6 SCIENCE · CHAPTER 7 · STUDY NOTES
Temperature and its Measurement
Read thermometers, understand scale divisions and compare temperatures carefully.
01 / EXPLORE & UNDERSTAND
Your hands can give different answers
Feeling warm is an observation, but it is not a precise temperature reading.
Different starting sensations, the same final water
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1. Compare the same water after different experiences
In the book’s demonstration, one hand first touches warm water and the other cold water. When both enter the middle container, the same water can feel cool to one and warm to the other. The earlier contact affects the sensation.
2. Use an instrument for a measurement
A thermometer provides a reading on a scale. Do not touch an unknown hot object to test its temperature. If a teacher demonstrates water comparisons, the water must be safe to touch.
Your turn
Question
Two hands disagree about the same water. Does that mean the water has two temperatures at the same point?
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02 / EXPLORE & UNDERSTAND
Always read the temperature unit
A number without its scale can be misleading.
1. Different numbers can mean the same temperature
37 °C and 98.6 °F represent the same temperature. Do not compare bare numbers from different scales as if the larger number always meant hotter.
2. Convert Celsius to kelvin
Add 273.15 to the Celsius value. For 20 °C: 20 + 273.15 = 293.15 K. Write K without a degree sign. Absolute zero is 0 K, equivalent to −273.15 °C; it is not 0 °C.
Your turn
Question
A label reads 300 K. Is it missing a degree sign? Explain.
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03 / EXPLORE & UNDERSTAND
Choose a thermometer made for the body
Clinical thermometers are designed for measuring body temperature.
A sensor and a digital display
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1. Follow the device’s instructions
A digital clinical thermometer uses an electronic sensor and displays a number. An adult should help use and clean it according to its instructions. The correct placement, cleaning method and waiting time depend on the device.
2. Keep the purpose and range in mind
A body thermometer is not a tool for boiling water or ice. Infrared thermometers can take a reading without contact, but still need correct positioning. Old mercury thermometers can release toxic mercury if broken; tell an adult instead of handling the spill.
Your turn
Question
Why should a digital body thermometer not be put in boiling water to “see what it says”?
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04 / EXPLORE & UNDERSTAND
37 °C is a reference, not an exact rule for everyone
A body-temperature reading needs context.
1. Notice the factors that can change a reading
The book uses 37 °C as a familiar reference. Healthy temperatures vary with the person, time of day and activity. The measurement site and method matter too.
2. Record, do not diagnose from one textbook number
When comparing records, keep the unit, method and time clear. A small difference from 37 °C is not by itself a diagnosis. If someone feels unwell, involve a trusted adult rather than treating a school comparison as a medical decision.
Your turn
Question
Two readings differ slightly but were taken at different times and with different methods. What should be checked before comparing them?
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05 / EXPLORE & UNDERSTAND
Read the liquid column
A liquid-in-glass laboratory thermometer has a bulb, a narrow tube and a marked scale.
1. Follow the liquid from the bulb
The bulb holds liquid connected to a thin column in the tube. As temperature changes, the column rises or falls. Read the mark level with the top of the column. Do not hold the bulb while taking a reading.
2. Check this instrument, not every thermometer
The book’s example runs from −10 °C to 110 °C. Other laboratory thermometers can have different ranges. A wide range does not automatically mean finer scale divisions.
Your turn
Question
A thermometer ranges from 0 °C to 50 °C. Can it measure −5 °C reliably?
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06 / EXPLORE & UNDERSTAND
Count the intervals between marks
The size of one small division tells you how to read the scale.
Three gaps can mean different temperatures
Keep the labelled marks at 20 °C and 30 °C. Change how many equal gaps fit between them.
(30 − 20) ÷ 5 = 2 °C per gap
Then count up from 20: 20 + 3 × 2 = 26 °C.
1. Subtract the labelled values
Suppose adjacent labelled marks are 20 °C and 30 °C. Their difference is 10 °C. Now count the equal gaps between them, not just the marks.
2. Divide the difference by the number of gaps
With five equal gaps, each gap represents 10 ÷ 5 = 2 °C. Three gaps above 20 °C is 26 °C. A different thermometer with ten gaps would have 1 °C divisions.
Your turn
Question
Between 10 °C and 20 °C there are twenty equal gaps. What does one gap represent?
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07 / EXPLORE & UNDERSTAND
Measure the water, not the beaker
A correct setup helps the reading represent the water you are studying.
Notice the bulb and the viewing level
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1. Keep the bulb in the water
In the teacher’s setup, immerse the bulb without touching the beaker’s bottom or sides. Keep the thermometer upright and wait for the reading to settle. Read with your eye level with the top of the column.
2. Read before taking it out
This laboratory thermometer does not hold the reading after removal. Its temperature starts changing towards the surroundings. Read it while the bulb remains in the water. Heated setups are handled by the teacher.
Your turn
Question
A learner removes the thermometer from warm water, then waits before reading it. What is the problem?
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08 / EXPLORE & UNDERSTAND
Temperature during melting and boiling
Heating does not always make the temperature rise at every moment.
1. Separate warming from changing state
As pure ice melts at a fixed pressure, its temperature stays nearly steady while solid and liquid are together. Pure water also stays near its boiling temperature while boiling at a fixed pressure. Energy is being used for the change of state.
2. Conditions affect the boiling point
Near standard atmospheric pressure, pure water boils around 100 °C. At higher places, lower air pressure allows boiling at a lower temperature. The book’s Shillong observations are below 100 °C; that alone does not prove the thermometer is faulty.
Your turn
Question
At a mountain laboratory, water boils below 100 °C. Must the reading be wrong?
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09 / EXPLORE & UNDERSTAND
Read daily highs and lows
Air temperature changes through a day and from day to day.
1. Keep the place and date with the reading
A maximum of 31 °C and minimum of 23 °C describe a day’s range, not two different scales. The difference is 8 °C. Without the date and place, the information is incomplete.
2. Use a series to notice patterns
Compare several days instead of one isolated reading. Temperature is only one part of weather; wind, rain and other observations matter too. Anna Mani helped develop weather-measuring instruments in India, showing why reliable measurements are important.
Your turn
Question
Day A ranges from 18 °C to 29 °C; day B from 22 °C to 30 °C. Which has the larger daily difference?
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Sign inNew here? Sign up freeCHAPTER RECAP
Take these ideas with you
- Touch gives a sensation; a thermometer gives a scale reading.
- Always include the unit: °C, °F or K.
- Choose a thermometer with a suitable purpose and range.
- Smallest division = labelled difference ÷ number of equal gaps.
- Read a laboratory thermometer while its bulb is still immersed.
- Body temperature and daily air temperature vary; context matters.
Use your understanding in a new situation
Question
A scale has eight equal gaps from 40 °C to 44 °C. What is one gap worth, and what is three gaps above 40 °C?
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A learner writes “the temperature is 98.6”. What is missing, and why does it matter?
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Sign inNew here? Sign up freeNCERT · Chapter source PDF, pages 12, 13, 14 · Original Learnijoy explanations and practice.