TS Board Telangana SCERT Class 7 Science Solutions 5th Lesson Heat-Measurement Textbook Questions and Answers.
TS 7th Class Science 5th Lesson Questions and Answers Telangana – Heat-Measurement
Question 1.
The body temperature of Srinath is 99°F. Is he suffering from fever? If so, why?
Answer:
Yes, Srinath is suffering from tèver, because his body temperature is beyond normal level (98.40 F). The rise in temperature may be due to other infections or by taking spoiled food and water.
Question 2.
Why do we use Mercury in the thermometer? Can water be used instead of Mercury ? What are the problems in using it?
Answer:
We use Mercury in the thermometer instead of water due to the following properties.
- Its expansion is uniform
- It is opaque and shining
- It does not stick to the sides of the glass tube
- It is a good conductor of heat.
If we use water instead of mercury, we can’t see the accurate reading of temperature, because water evaporates on high heating. It doesn’t show expansion clearly.
Question 3.
Temperature of Srinagar (J & K) is – 4°C and Paderu (AP) is 3°C. Which of them has greater temperature ? What is the difference between the temperatures of these too places? (Conceptual Understanding)
Answer:
The temperature of Paderu (AP) is 7°C greater than Srinagar.
The temperature in Kashmir ( – 4°C) goes beyond the freezing point.
The temperature in Paderu is very near to 0°C (freezing point).
Question 4.
During winter mornings why do people stand in the Sun ? Explain.
Answer:
In winter, we feel cold inside the house due to less temperature Hence. people stand in the sunlight to get some heat.
Question 5.
After walking some distance on a hot summer day, why do we prefer to go into the shade?
Answer:
After walking some distance on a hot summer day, we feel very tired. The temperature of the body is lesser compared to out side hot weather. In order to withstand such hot conditions, we feel to stay in the shade until we get relaxed. So, we prefer to go into the shade and get relaxed.
Question 6.
Srikanth takes a sip of cold drink and feels the chill. Guess what its temperature is? Try to measure it.
Answer:
The temperature of cold drink will be at about 5°C. If we measure this temperature by using thermometer, it will be more or less 5°C.
Question 7.
Jyothi was prepared to measure the temperature of hot water with a clinical thermometer. Is it right or wrong ? Why?
Answer:
- It is wrong, because in a clinical thermometer, we can measure the temperature only upto 45°C.
- But the temperature of hot water will be above 45°C.
- If we measure the temperature of hot water with a clinical thermometer, it will break.
- Clinical thermometer is designed to measure only our body temperature.
Question 8.
Swathi kept a laboratory thermometer in hot water for sometime and took it out to read the temperature. Rani said it was a wrong way of measuring
temperature. Do you agree with Rani? Explain your answer.
Answer:
Yes, I agree with Rani.
- Laboratory thermometer is suspended for sometime in the boiling vessel with the help of ring stand.
- Therefore, we will measure the temperature of boiling waler until it reaches boiling point (100°C)
Question 9.
Why do we jerk a clinical thermometer before we measure body temperature?
Answer:
The thermometer has a neck in the fluid column. So the fluid mercury column would not come down readily after being taken out from the patient’s mouth. Therefore, jerking the thermometer is to ensure it is properly reset.
Question 10.
Heat energy is converted into other forms of energy. Give some examples.
Answer:
Heat energy is converted into other forms of energy. Some of the examples are:
- Heat energy in the steam engine is converted to mechanical energy to move the vehicles.
- Solar energy is converted into electrical energy.
Question 11.
Prathima said ‘Heat is a form of energy’. How do you support her?
Answer:
Heat is a form of energy’ because different kinds of energies are being converted to heat and in the same way heat energy is converted into other forms of energy.
Ex :
- Running of steam engine by converting heat energy into mechanical enerqy.
- Production of electricity in thermal power stations by burning of coal.
Question 12.
Why is a clinical thermometer not used to measure the temperature of air?
Answer:
For the measurement of temperature, the bulb of clinical thermometer needs to be in close contact with that object. So we can not measure the temperature of air by using clincal thermometer.
Question 13.
Fill in the blanks.
a. Doctor uses ………………….. thermometer to measure the human body temperature.
b. At room temperature mercury is in ………………….. state.
c. Heat energy transfers from ………………….. to …………………..
d. -7°C temperature is ………………….. than 0°C temperature.
Answer:
a. clinical
b. liquid
c. hotter body, colder body
d. lesser
Question 14.
Match the following.
i) Clinical thermometer (E) A) A form of energy
ii) Normal temperature of human body (C) B) 100°C
iii) Heat (A) C) 37°C
iv) Boiling point of water (B) D) 0°C
v) Melting point of water (D) E) Kink
Answer:
(i) – E, (ii) – C, (iii) – A, (iv) – D
Question 15.
Use the Thermometer and record the temperature in your school daily at mid-day meals time in the following table. Record temperature for a month.
- On which day was the temperature highest ? What could be the reason?
- On which day was the temperature lowest ? What could be the reason?
- What was the average temperature during the month?
Answer:
On 13-03-2018, temperature was highest.
On 15-03-2018, temperature was lowest because of cloudy atmosphere.
Average temperature = 35.5°C
Question 16.
Draw the diagram of a clinical thermometer and label its parts, What is the use of kink in a clinical thermometer?
Answer:
Kuir prevents mercury level from falling on its own.
Question 17.
Draw the diagram of a laboratory thermometer and label its parts. How does it differ from a clinical thermometer?
Answer:
- Clinical thermometer has ‘kink’ but a laboratory thermometer does not have, which prevents mercury level from falling on its own.
- The range of temperatures is also different.
- In a laboratory thermometer, the range of temperature is marked from -10°C to 110°C.
- In clinical thermometer, the temperature is marked from 35°C and ends with 45°C.
Question 18.
Measure the body temperature between fingers, under the tongue, armpit, folded hands, folded legs etc. Is it the same ? Does the body temperature remain the same after jumping ten times ? Why?
(Or)
Tabulate the temperatures you measured at various parts of the body. Write a report
Answer:
| Body Parts | Body Temperature (°F) |
| 1. Between fingers 2. Under the tongue 3. Armpit 4. Folded hands 5. Folded legs |
95°F 98.8°F 98.4°F 97.9°F 97.5°F |
No, the temperature varies at different parts of body. After jumping ten times, the body temperature increases by 0.2°F because while jumping, muscular energy is converted into heat energy.
Question 19.
Collect information from hospital/health centre about the precautions to be taken while reading temperature with a clinical thermometer.
(Or)
What precautions you came to know from hospital while reading temperature with a clinical thermometer? (Information Skills and Projects)
Answer:
Precautions to be taken while reading temperature with a clinical thermometer:
- Hold it firmly by the end and give it a few jerks. It is to bring the mercury column to the normal level.
- While reading the temperature, place the thermometer under patient’s tongue or armpit. After one minute, take it out and note the reading.
- Wash the thermometer with an antiseptic solution for every use.
Question 20.
Measure the temperature of water in normal conditions. If you add the following substance to the water, do you find any difference in temperature? Predict and verify.
| Water temperature in Celsius | Water (100ml each time) mixed with two table spoonful of each | Prediction | Temperature of the solution immediately after mixing the substance |
| Glucose | Decrease | ||
| Washing powder | |||
| Baking soda | |||
| Sugar | |||
| Common salt |
Answer:
| Water temperature in Celsius | Water (100ml each time) mixed with Two tablespoonful of each | Prediction
|
Temperature of the solution immediately after mixing the substance |
| 30°C | Glucose | Decrease | 25°C |
| 30°C | Washing powder | Increase | 36°C |
| 30°C | Baking soda | Increase | 34°C |
| 30°C | Sugar | Does not change | 30°C |
| 30°C | Common salt | Does not change | 30°C |
Yes, by adding some substances, the temperature of water increases and for some substances, it decreases because of changes in the chemical reaction.
Let Us Do
1. Let us do this :
Some of the objects are given in the table. Mark these objects as hot or cold?
| Object | Cold | Hot |
| Ice Cream | ||
| Fruit Juice | ||
| Metal Chair kept in the sun | ||
| Spoon in cup of hot tea |
Answer:
| Object | Cold | Hot |
| Ice Cream | ✓ | |
| Fruit Juice | ✓ | |
| Metal Chair kept in the sun | ✓ | |
| Spoon in cup of hot tea | ✓ |
2. Let us do this:
Conservation of energy.
Question 1.
Did you ever bathe with cold water during winter? What happens?
Answer:
We will feel very cold. We feel chill in severe winter.
Question 2.
What do you do to protect yourself from cold?
Answer:
We protect ourselves from cold by wearing woollen clothes.
Question 3.
How do you get hot water in winter?
Answer:
By heating water.
Question 4.
Generally we heat water to get hot water. How do you heat water? What sources do you use?
Answer:
They are heater, gas stove, fire wood, solar heater etc. We heat water with different heat energy giving sources.
3. Let us do this:
Question 1.
Do you find any difference in temperature of air in shadow and in the sun?
Measure temperature of air using a thermometer. What will you do to keep thermometer in close contact with air?
Record your observations in the following table.
| Observation | Recorded Temperature |
| Air in the shade (at 12 noon) | 32°C |
| Air in the sun (at 12 noon) | 37°C |
| Morning (at 8 am) | 28°C |
| Night (at 8 pm) | 33°C |
The thermometer is help up in the air. The mercury bulb of the thermometer is exposed to air. Therefore the mercury expansion is clearly seen. Also the reading is taken very easily.
Question 2.
What did you observe ? Is there any difference in temperature with variation of time or place ?
Answer:
Yes, during morning and night times temperature is low, whereas afternoon temperature is high.
Question 3.
Why do you use an umbrella in the hot sun during summer ?
Answer:
To protect our body from hot sun during summer. Umbrella stops the sun’s heat falling on our body.
Question 4.
Feel the body temperature of some of your friends by placing your hand on their forehead. Estimate the temperature and record it, in the table. Measure it now with clinical thermometer. Record your observations in table. Make sure that you have cleaned the thermometer before each measurement.
Answer:
| Name of the Student | Estimated Temperature by touching | Temperature measured with clinical thermometer |
| Srinivas | 99°F | 98.7°F |
| Kiran | 98.6°F | 98.6°F |
| Vardhan | 97°F | 98.7°F |
| Mvthresh | 100°F | 98.8°F |
| Satya | 98°F | 98.4°F |
Compare the values in the table after completion of recording.
1. What do you observe in the table ?
Answer: Temperature will differ from person to person.
2. Are the estimated temperature and measured temperature same ?
Answer: No.
3. Is the body temperature of every person 37°C (98.4°F) ?
Answer: No.
4. What is the average body temperature of your friends ?
Answer: 98.6°F.
5. Do you know ?
Thermister thermometer. It is available in market to measure the human body temperatures, particularly for infants and children. Can you guess why ?
Answer:
Clinical thermometer contains mercury which is a toxic substance and is very difficult to dispose of, if a thermometer breaks. So, it is harmful to measure temperature of infants and children.
TS 7th Class Science 5th Lesson Notes Heat-Measurement
- Heat energy : Heat is a form of energy that transfers among particles.
- Temperature : Temperature is a measure of the degree of hotness or coldness of an object.
- Thermometer : A thermometer is a device that measures temperature.
- Fahrenheit Scale : The scale of measuring temperature invented by Fahrenheit. In clinical thermometer, this scale starts from 95°F and ends at 110°F.
- Celsius Scale : The scale of measuring temperature invented by Celsius. In clinical thermometer, this scale starts from 35°C and ends at 45°C.
- Clinical thermometer : Doctors use a clinical thermometer to measure the human body temperature.
- Expansion : It is a phenomenon which is related to the working of clinical thermometer.
(or)
It is a phenomenon where matter increases its volume on constant heating. - The energy which makes an object appear hot or cold is called heat.
- Heatflows front an object at higher temperature to another at liver temperature.
- Different kinds of energies like mechanical, chemical, solar energies are being converted to heat. In the same way, heat energy can be converted into other forms of energy.
- We use thermometers to measure temperature.
- Mercury and alcohol are used as thermometer liquids in thermometers.
- Thermometer is based on the fact that matter expands on heating.
- The melting point of ice is 0°C and boiling point of water is 100°C.
- First thermometer was invented by Galileo in 1593 AD.
- The normal temperature of human body is 36.9° C/37°C (98.4°F/ 98.6°F)
- The maximum and minimum temperatures of a day are measured by Six’s maximum minimum thermometer.
- Some other types of thermometers are thermister thermometer, digital thermometer.
- Relation between Celsius temperature and Fahrenheit temperature:
\(\frac{C}{F}=\frac{F-32}{9}\)