EN हिं

NCERT Solutions Curiosity Chapter 7 Extended activities and projects — Learning further

Book page 140 & 141 Updated on2026-09-05

Q1.
Gather information from the Internet and find out how the body temperature of animals, such as a cat, dog, horse, camel, cow and buffalo, is measured. If there is any veterinary hospital in your vicinity, you may visit to see the body temperature of animals being measured.
Answer

How it is done: a veterinary doctor uses a digital clinical thermometer (or the old mercury type) and inserts the lubricated tip gently into the animal’s rectum, holding it there for about a minute. The mouth is not used, for obvious reasons, and the armpit reading is unreliable in furry animals. Some vets also use a non-contact infrared thermometer aimed at the ear or the flank for a quick check.

Approximate normal body temperatures to compare your findings with (all in °C):

AnimalUsual normal body temperatureCompared with a human (37.0 °C)
Catabout 38 °C to 39 °Chigher
Dogabout 38 °C to 39 °Chigher
Horseabout 37.5 °C to 38.5 °Cslightly higher
Camelabout 34 °C to 40 °Cvaries a lot through the day
Cowabout 38 °C to 39 °Chigher
Buffaloabout 37.5 °C to 39 °Chigher
The interesting one is the camel: most animals hold their temperature almost fixed. A camel in the desert lets its body temperature drift up through the hot day and fall again at night. By storing the heat instead of sweating it away, it saves a great deal of water.
Tip: If you visit a veterinary hospital, ask the doctor two things — what the normal temperature of that animal is, and how much above normal counts as fever. Write the answers in your notebook with the unit °C.
Q2.
Find out which places in India are usually regarded to be the coldest and hottest. Also, find out the minimum and the maximum temperatures recorded for these places.
Answer

Usually regarded as the coldest:

  • Dras, in the Kargil district of Ladakh — often called the coldest inhabited place in India. Temperatures near –45 °C have been recorded there.
  • The Siachen Glacier is colder still, but nobody lives there permanently.
  • Leh (Ladakh), Sela Pass (Arunachal Pradesh) and Keylong (Himachal Pradesh) are other very cold places.

Usually regarded as the hottest:

  • Phalodi, in Rajasthan — where India’s highest reliably recorded temperature, about 51 °C, was measured in May 2016.
  • Churu and Bikaner in Rajasthan, and Nagpur and Titlagarh (Odisha), regularly cross 47 °C in summer.
Difference between the two extremes
= 51 °C – (–45 °C)
= 51 °C + 45 °C
= 96 °C — almost the whole range of a laboratory thermometer!
Check it yourself: Records change. Look up the India Meteorological Department (IMD) website for the latest all-time maximum and minimum for these stations, and note the date of each record along with the temperature.
Q3.
Various planets in our Solar System are at different distances from the Sun. Search the Internet and make a table with the planets, their distances from the Sun (in increasing order) and their temperatures written. Does the average temperature of planets decrease as their distance from the Sun increases? If it is not true for any planet, find out for which planet and why.
Answer

Here is the table, with the planets in increasing order of distance:

PlanetAverage distance from the SunAverage surface temperature
Mercury58 million kmabout 167 °C
Venus108 million kmabout 464 °C
Earth150 million kmabout 15 °C
Mars228 million kmabout –65 °C
Jupiter778 million kmabout –110 °C
Saturn1430 million kmabout –140 °C
Uranus2870 million kmabout –195 °C
Neptune4500 million kmabout –200 °C

Yes — as a general rule, the farther a planet is from the Sun, the colder it is. From Earth outwards the temperature falls steadily, all the way to about –200 °C at Neptune.

But there is one clear exception: Venus. Venus is farther from the Sun than Mercury, yet it is by far the hottest planet — about 464 °C against Mercury’s 167 °C.

Why Venus breaks the rule: Venus is wrapped in a thick atmosphere of carbon dioxide. Sunlight gets in, warms the surface, but the heat cannot escape back into space — the atmosphere traps it. This is the greenhouse effect, and on Venus it is so strong that the planet stays hot enough to melt lead. Mercury, by contrast, has almost no atmosphere, so all its heat escapes at night.
Did you know? Because it has no blanket of air, Mercury swings between roughly 430 °C in the day and –180 °C at night — the biggest temperature swing of any planet in the Solar System.
Q4.
Hang a room thermometer in your classroom. Set up the apparatus, as shown in Fig. 7.11, near the thermometer hung on the wall. Take the readings of thermometers 1 and 2 three times during the day, say, first period, lunch break, and last period. Record your readings. Compare the readings and draw your conclusions. Repeat this for two weeks.
Answer

What to set up: Thermometer 1 is the room thermometer on the wall; Thermometer 2 is a laboratory thermometer clamped in a stand with its bulb dipped in a beaker of water, standing near the wall. Both must be read with the eye in line with the top of the column.

Sample record for one day (make a fresh row for each day, for two weeks):

Time of dayThermometer 1 — room airThermometer 2 — waterDifference
First period (8 am)22 °C23 °C1 °C
Lunch break (12 noon)29 °C27 °C2 °C
Last period (3 pm)31 °C29 °C2 °C

Conclusions you can expect to draw:

  • Both temperatures rise from morning to afternoon and are highest in the last period, because the Sun has been heating the building all day.
  • The water temperature follows the air temperature but lags behind it — it is a little higher than the air in the cool morning and a little lower in the hot afternoon.
  • Over two weeks, days that felt hot show higher readings on both thermometers, so the water is a fair, if slow, record of room temperature.
Why the water lags: water takes in and gives out a great deal of heat for every degree it changes. So when the air warms quickly, the water has not caught up yet — and when the air cools at night, the water is still holding yesterday’s warmth. This is the same reason why places near the sea have milder weather than places inland.
Tip: Keep the beaker away from the window. Direct sunlight falling on it would heat the water on its own and spoil the comparison.
Was this helpful? Report an error