6ನೇ ತರಗತಿ ವಿಜ್ಞಾನ (Curiosity ಭಾಗ-2) ಪಠ್ಯಪುಸ್ತಕದ 7ನೇ ಅಧ್ಯಾಯ “Temperature and its Measurement” (ತಾಪಮಾನ ಮತ್ತು ಅದರ ಅಳತೆ) ಪಾಠವನ್ನು ಮಕ್ಕಳು ಸುಲಭವಾಗಿ ಮತ್ತು ಖುಷಿಯಿಂದ ಕಲಿಯಲು ಇಲ್ಲಿ ಸಿದ್ಧಪಡಿಸಲಾಗಿದೆ. ಸರಳ ಭಾಷೆಯ ಪಾಠದ ವಿವರಣೆ, ಬಣ್ಣಬಣ್ಣದ ಚಿತ್ರಗಳು, ಅನಿಮೇಷನ್‌ಗಳು, ಆಟದ ರೂಪದ ರಸಪ್ರಶ್ನೆ, ಥರ್ಮಾಮೀಟರ್ ಓದುವ ಆಟ, ಹಾಗೂ ಎಲ್ಲಾ ಅಭ್ಯಾಸ ಪ್ರಶ್ನೆಗಳಿಗೆ ಸ್ಪಷ್ಟ ಉತ್ತರಗಳು ಇಲ್ಲಿವೆ. ಜೊತೆಗೆ, ಪಾಠ ಮತ್ತು ಪ್ರಶ್ನೋತ್ತರಗಳ PDF ಅನ್ನು ಉಚಿತವಾಗಿ ಡೌನ್‌ಲೋಡ್ ಮಾಡಿಕೊಳ್ಳಬಹುದು. ಶಿಕ್ಷಕರು, ವಿದ್ಯಾರ್ಥಿಗಳು ಮತ್ತು ಪೋಷಕರಿಗೆ ಇದು ಉಪಯುಕ್ತವಾಗಲಿದೆ.
Temperature and its Measurement
The full lesson explained in simple words with drawings, followed by answers to every in-text question, activity and exercise.
Questions and answers: in-text questions, activities and “Let us enhance our learning” (exercises 1 to 14).
“Wrong measurements are worse than no measurements at all.”Anna Mani, the Weather Woman of India
The Lesson
Read this first. Every part of the chapter is explained here, in order.
A story to begin
Lambok and his elder sister Phiban live in Shillong. One day after school, Lambok said he felt feverish. Phiban touched his forehead and thought he might have a fever. To be sure, she took out the thermometer, washed its tip with soap and water, and measured his temperature. It was normal. She washed and dried the tip again before putting it away.
Think: can we always tell that a person has fever just by touching them? Let us find out.
7.1 Hot or cold?
Some things are hotter than others. In summer, tap water feels hotter than water from a matka (earthen pot) or a refrigerator. We can feel this by touching. But is our sense of touch always correct?
- Take three large containers: A with warm water, B with tap water, C with ice-cold water.
- Predict first, then do it: keep your right hand in A and your left hand in C for 1–2 minutes.
- Take both hands out and put them in B at the same time.
What will the right hand (from warm water A) feel in B?
- Cold
- Warm
What will the left hand (from ice-cold water C) feel in B?
- Cold
- Warm
Observation: the right hand (from warm water) feels B is cold. The left hand (from ice-cold water) feels B is warm.
We cannot always rely on our sense of touch to decide whether something is hot or cold.
7.2 Temperature
Temperature is a reliable measure of how hot or cold a body is.
- A hotter body has a higher temperature than a colder body.
- The difference in temperature tells us how much hotter one body is than another.
- The device used to measure temperature is called a thermometer.
We usually come across two kinds of thermometers:
| Clinical thermometer | Laboratory thermometer | |
|---|---|---|
| Used for | Human body temperature | Many other things: water, ice, air and more |
| Usual range | 35 °C to 42 °C | –10 °C to 110 °C |
| How it shows | Digital display (runs on battery) | Liquid column against a Celsius scale |
| Reading | Taken after it beeps | Read while the bulb is still in the substance |
7.3 Measuring temperature
7.3.1 Clinical thermometer
The thermometer used to measure body temperature is a clinical thermometer. Most of them today are digital clinical thermometers. They run on batteries and show the temperature as numbers when the tip touches the body.
Clinical thermometers usually use the Celsius scale. On this scale the unit of temperature is the degree Celsius, written °C.
- Earlier, mercury thermometers were used. Mercury is very poisonous and hard to dispose of safely if the thermometer breaks.
- Digital thermometers have no such risk, and their numbers are easier to read. They measure temperature with heat sensors.
- During the COVID-19 pandemic, non-contact (infrared) thermometers were used. They measure temperature from a distance without touching the body, which reduces the spread of disease.
- Wash your hands and the tip of the digital thermometer with soap and water.
- Press the reset button.
- Place the tip under the tongue and close the mouth.
- Wait until it beeps or flashes a light.
- Take it out and read the display. Record it in a table.
- Clean the tip again with soap and water and dry it. Repeat for your friends.
- Read the instruction manual before use.
- Wash the tip with soap and water before and after use.
- Keep the display part out of water while washing.
- Do not hold the thermometer by its tip.
The normal temperature of a healthy human body is taken as 37.0 °C. But this is an average of many healthy people, so a healthy person may show a slightly different value.
- Body temperature depends on age, time of the day and activity level.
- Small children usually have slightly higher temperatures; healthy old people usually slightly lower.
- Human body temperature normally does not go below 35 °C or above 42 °C.
- For small children or old people, the thermometer can be kept in the armpit. This reading is about 0.5 °C to 1 °C lower than the actual body temperature.
Three temperature scales
- Celsius scale: unit degree Celsius (°C).
- Fahrenheit scale: unit degree Fahrenheit (°F). 37.0 °C is the same as 98.6 °F. This scale is not used in most scientific work now.
- Kelvin scale: unit kelvin (K). The SI unit of temperature is kelvin.
All three scales are named after the scientists who made them.
Slide to change the temperature. See it on all three scales.
To change Celsius to kelvin, add 273.15:
Temperature in K = Temperature in °C + 273.15
Example: 37 °C = 37 + 273.15 = 310.15 K
- Names of scales start with a capital letter: Celsius scale, Fahrenheit scale, Kelvin scale.
- In unit names, “degree” is small and Celsius and Fahrenheit are capital: degree Celsius, degree Fahrenheit. The unit kelvin is written in small letters.
- Symbols are capital letters: °C, °F, K. Do not put the degree sign with K.
- No full stop after the symbol, except at the end of a sentence.
- Leave a space between the number and the unit: 37.0 °C, not 37.0°C.
- For more than one degree, write “degrees”: 40 degrees Celsius.
Before thermometers, fever was guessed from the pulse rate, since fever changes it. But many other things also change the pulse rate, so it is not a reliable sign of fever.
Can a clinical thermometer measure boiling water or ice? No. Their temperatures are outside its range. For such temperatures we use a laboratory thermometer.
7.3.2 Laboratory thermometer
A laboratory thermometer is a long, narrow, uniform glass tube that is sealed. At one end is a bulb containing a liquid. A thin column of liquid goes up the tube, and a Celsius scale is marked along it. The column rises when it gets hotter and falls when it gets colder. The mark where the top of the liquid column stands is the temperature reading.
The liquid in a laboratory thermometer is usually alcohol (coloured red so it is easy to see) or mercury.
Look at a laboratory thermometer and note the lowest and highest temperatures on its scale. For the thermometer above, the lowest is –10 °C and the highest is 110 °C, so its range is –10 °C to 110 °C.
- Handle with care. It can break if it hits something hard.
- Do not hold it by the bulb.
- Difference between two big marks: 10 °C
- Small divisions between them: 10
- One small division: 10 °C ÷ 10 = 1 °C
- So the smallest value this thermometer can read is 1 °C.
Different thermometers can have different ranges and smallest divisions, so always check the thermometer before using it.
Correct way to measure with a laboratory thermometer
- The bulb should not touch the bottom or the sides of the container.
- Hold the thermometer vertically. Do not tilt it.
- Read the temperature while the bulb is still in the water.
- Keep your eye in line with the top of the liquid column while reading.
- Take warm water in a beaker and dip the thermometer so that the bulb is in the water.
- Watch the liquid column rise. When it stops rising, note the reading. Do not wait too long, or the water itself will cool.
- Take the thermometer out and watch the column.
So the temperature must be read while the thermometer is in the water. This is also why a laboratory thermometer is not used to measure body temperature.
Read both thermometers again after some time. The readings do not change: the temperature stays constant while water is boiling and while ice is melting.
This activity must be done only under the teacher’s supervision. Do not touch the setups.
Phiban and her classmates in Shillong measured the temperature of the same boiling water:
| Name | Phiban | Shemphang | Onestar | Kloi | Bandarisha |
|---|---|---|---|---|---|
| Boiling water (°C) | 97.8 | 98.0 | 97.9 | 98.0 | 98.1 |
The readings are slightly different. A likely reason is that not everyone followed the correct way of reading the thermometer.
7.3.3 Air temperature
Thermometers hung on the walls of laboratories, clinics and hospitals are room thermometers. They give an approximate idea of the room temperature. Weather reports in newspapers, on TV and on the internet give the maximum and minimum air temperature of the day.
Note the maximum and minimum air temperature of a place from weather reports for 10 days, and compare them.
These temperatures change every day because weather depends on many factors. Generally they rise as summer comes and fall in winter.
Air temperature is an important weather measurement. Weather stations all over the world record it. This data, along with other measurements, is used for weather forecasts.
Know a scientist: Anna Mani (1918–2001)
- Indian scientist known as the Weather Woman of India.
- She invented and built many weather-measuring instruments, so India depended less on other countries for them.
- She studied how India could use wind and solar energy. Her work helped India become a global leader in renewable energy.
The core of the Sun is about 15 million °C. There is no known upper limit to temperature. But there is a lowest possible temperature, close to –273.15 °C (0 K), called absolute zero.
Game: Read the thermometer
Look where the red line stops and pick the right reading. 5 rounds. Win a star for each correct answer!
Keywords
Summary
- The temperature of a body tells us how hot or cold it is.
- The three common scales are Celsius (°C), Fahrenheit (°F) and Kelvin (K).
- The SI unit of temperature is kelvin.
- A clinical thermometer measures body temperature.
- Normal temperature of a healthy adult is taken as 37.0 °C or 98.6 °F.
- Laboratory thermometers usually have a range of –10 °C to 110 °C.
Learning further (projects)
- Find out how the body temperature of animals like cats, dogs, cows and buffaloes is measured. Visit a nearby veterinary hospital if you can.
- Find the coldest and hottest places in India and their recorded minimum and maximum temperatures.
- Make a table of planets, their distance from the Sun and their temperatures. Does temperature fall as distance increases? Find the planet that does not follow this, and why.
- Hang a room thermometer in class and keep a laboratory thermometer in a beaker of water near it. Take readings three times a day for two weeks and compare.
Questions & Answers
Part A In-text questions and activities
Can it always be correctly judged that a person has fever only by touching the person?
Page 1No. Our sense of touch is not reliable. To know correctly, we measure the temperature with a thermometer.
Activity 7.1: Dip the right hand in warm water (A) and the left hand in ice-cold water (C) for 1–2 minutes, then put both hands in tap water (B). What will each hand feel?
Page 2- Right hand (from warm water A) feels the water in B is cold.
- Left hand (from ice-cold water C) feels the same water in B is warm.
Inference: the same water feels different to the two hands, so we cannot always rely on our sense of touch to decide whether a body is hot or cold.
Then how do we find out how hot or cold a body is?
Page 3By measuring its temperature with a thermometer. Temperature is a reliable measure of how hot or cold a body is.
Activity 7.2: Measure the body temperature of 10 persons with a digital clinical thermometer. Is it 37.0 °C for everyone?
Pages 5–6Steps: wash the tip → reset → place under the tongue → wait for the beep → read → record → clean the tip.
- Most readings are close to 37.0 °C but not exactly the same.
- 37.0 °C is the average of many healthy people. Body temperature depends on age, time of the day and activity level.
Do small children generally have slightly higher body temperatures as compared to adults?
Page 6Yes. Small children generally have slightly higher body temperatures than adults.
Do old people, even when healthy, generally have lower body temperatures than young adults?
Page 6Yes. Healthy old people generally have slightly lower body temperatures than young adults.
A friend’s digital thermometer shows the normal temperature of a healthy human body as 98.6 °F. What is the reason for this difference?
Page 6That thermometer uses the Fahrenheit scale. 37.0 °C on the Celsius scale is the same temperature as 98.6 °F on the Fahrenheit scale. Only the scale is different.
Can a clinical thermometer be used for measuring the temperature of boiling water or of ice?
Page 7No. The temperatures of boiling water (about 100 °C) and ice (about 0 °C) are outside the range of a clinical thermometer (about 35 °C to 42 °C).
How can we measure temperatures beyond the range of a clinical thermometer?
Page 7By using a laboratory thermometer. Its range is usually –10 °C to 110 °C.
Activity 7.3: Find the temperature range of a laboratory thermometer.
Page 8- Lowest temperature it can measure: –10 °C
- Highest temperature it can measure: 110 °C
- Range: –10 °C to 110 °C
Activity 7.4: Find the smallest value a laboratory thermometer can read.
Page 9- Temperature difference between two bigger marks: 10 °C
- Number of small divisions between them: 10
- One small division: 10 °C ÷ 10 = 1 °C
- Smallest value the thermometer can read: 1 °C
Activity 7.5: Measure the temperature of warm water. What happens to the liquid column when the thermometer is taken out?
Page 10- The liquid column rises and then stops. Note the reading at that point.
- When taken out of the water, the column starts to fall.
- So the temperature must be read while the bulb is still in the water.
Correct way: hold the thermometer vertically, keep the bulb off the bottom and sides of the beaker, and keep the eye in line with the top of the liquid column.
Can we use a laboratory thermometer for measuring the body temperature of a person?
Page 10No, because:
- its liquid column starts falling as soon as it is taken away from the body, so we cannot read it correctly;
- it is long and made of glass, so it is not safe or convenient to keep in the mouth;
- clinical thermometers are made for measuring body temperature.
More to do: What are the temperatures of ice and boiling water? Are they the same after some time?
Page 11- Melting ice: about 0 °C
- Boiling water: about 100 °C
- After some time, the readings do not change. The temperature stays constant while water is boiling and while ice is melting.
Activity 7.6: Why are there differences in the boiling-water readings (97.8, 98.0, 97.9, 98.0, 98.1 °C) taken by Phiban and her classmates?
Pages 11–12The readings are close but not equal. Possible reasons:
- The correct way of reading the thermometer was not followed by every student.
- The eye was not in line with the top of the liquid column.
- The bulb touched the bottom or sides of the vessel.
- The thermometer was tilted, or taken out of the water before reading.
Teacher’s note (not stated in the textbook): all readings are a little below 100 °C because Shillong is a hill station. Water boils at a slightly lower temperature at high places.
Activity 7.7: Record the maximum and minimum air temperature for 10 days. Do they stay at the same level?
Pages 12–13No. They change every day because weather depends on several factors. Generally, the temperature rises as summer approaches and falls during winter.
Part B Let us enhance our learning · pages 15–18
The normal temperature of a healthy human being is close to ________.
Page 15- (i) 98.6 °C
- (ii) 37.0 °C
- (iii) 32.0 °C
- (iv) 27.0 °C
(ii) 37.0 °C
37 °C is the same temperature as ________.
Page 15- (i) 97.4 °F
- (ii) 97.6 °F
- (iii) 98.4 °F
- (iv) 98.6 °F
(iv) 98.6 °F
Fill in the blanks: (i) The hotness or coldness of a system is determined by its ______. (ii) The temperature of ice-cold water cannot be measured by a ______ thermometer. (iii) The unit of temperature is degree ______.
Page 15- temperature
- clinical
- Celsius
The range of a laboratory thermometer is usually ________.
Page 15- (i) 10 °C to 100 °C
- (ii) –10 °C to 110 °C
- (iii) 32 °C to 45 °C
- (iv) 35 °C to 42 °C
(ii) –10 °C to 110 °C
Four students used a laboratory thermometer to measure the temperature of water (Fig. 7.6). Who followed the correct way? (i) Student 1 (ii) Student 2 (iii) Student 3 (iv) Student 4
Pages 15–16- (i) Student 1
- (ii) Student 2
- (iii) Student 3
- (iv) Student 4
(ii) Student 2
Colour the red column on the drawings of thermometers (Fig. 7.7) for 14 °C, 17 °C and 7.5 °C.
Page 16Tap on each thermometer where the red column should stop. Look at the size of the small divisions first.
First find the value of one small division on each thermometer, then colour up to the right mark.
- 14 °C: 5 divisions between 10 and 20, so 1 division = 2 °C. Colour 2 divisions above 10.
- 17 °C: 10 divisions between 10 and 20, so 1 division = 1 °C. Colour 7 divisions above 10.
- 7.5 °C: 20 divisions between 0 and 10, so 1 division = 0.5 °C. Colour 15 divisions above 0.
Observe the thermometer in Fig. 7.8. (i) What type of thermometer is it? (ii) What is its reading? (iii) What is the smallest value it can measure?
Page 16- Laboratory thermometer. Its scale starts at –10 °C, far below the range of a clinical thermometer.
- Reading: 26 °C (6 small divisions after the 20 mark).
- Smallest value: 1 °C. There are 10 divisions between 0 and 10, so 10 ÷ 10 = 1 °C
A laboratory thermometer is not used to measure our body temperature. Give a reason.
Page 16- Its liquid column starts falling as soon as it is taken out of the mouth, so the correct reading cannot be taken.
- It must be read while still in contact, which is not possible when it is inside the mouth.
- It is long and made of glass, so it is unsafe and inconvenient for this use.
Vaishnavi’s body temperature record for three days is given below. (i) What was her highest recorded temperature? (ii) On which day and at what time was it recorded? (iii) On which day did her temperature return to normal?
Page 17| Day | 7 am | 10 am | 1 pm | 4 pm | 7 pm | 10 pm |
|---|---|---|---|---|---|---|
| One | 38.0 | 37.8 | 38.0 | 38.0 | 40.0 | 39.0 |
| Two | 38.6 | 38.8 | 39.0 | 39.0 | 39.0 | 38.0 |
| Three | 37.6 | 37.4 | 37.2 | 37.0 | 36.8 | 36.6 |
- Highest recorded temperature: 40.0 °C
- Recorded on Day One at 7 pm.
- Her temperature returned to normal on Day Three. It came down to 37.0 °C at 4 pm.
If you have to measure the temperature 22.5 °C, which of the three thermometers (Fig. 7.9) will you use? Explain.
Page 17- (a)
- (b)
- (c)
Thermometer (b).
| Thermometer | Divisions between 0 and 10 | One division | Can show 22.5 °C? |
|---|---|---|---|
| (a) | 10 | 1 °C | No |
| (b) | 20 | 0.5 °C | Yes |
| (c) | 5 | 2 °C | No |
Only (b) has a mark for every half degree, so 22.5 °C can be read exactly on it.
The temperature shown by the thermometer in Fig. 7.10 is ________.
Page 18- (i) 28.0 °C
- (ii) 27.5 °C
- (iii) 26.5 °C
- (iv) 25.3 °C
(ii) 27.5 °C. Each small division is 0.5 °C, and the red column ends 5 divisions after the 25 mark: 25 + (5 × 0.5) = 27.5 °C
A laboratory thermometer has 50 divisions between 0 °C and 100 °C. What does each division of this thermometer measure?
Page 18- Temperature difference = 100 °C – 0 °C = 100 °C
- Number of divisions = 50
- One division = 100 ÷ 50 = 2 °C
Each division measures 2 °C.
Draw the scale of a thermometer in which the smallest division reads 0.5 °C. You may draw only the portion between 10 °C and 20 °C.
Page 18Difference = 20 – 10 = 10 °C. Number of divisions = 10 ÷ 0.5 = 20
Draw long marks at 10, 15 and 20 °C, medium marks at each whole degree, and short marks at each half degree. That gives 20 equal small divisions.
Komal tells you that she has a fever of 101 degrees. Does she mean it on the Celsius scale or Fahrenheit scale?
Page 18- Celsius scale
- Fahrenheit scale
She means the Fahrenheit scale.
- Normal body temperature is 98.6 °F, so 101 °F is a mild fever (about 38.3 °C).
- 101 °C would be hotter than boiling water (100 °C). Human body temperature normally stays between 35 °C and 42 °C.
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