Heat and Temperature

 

What is Heat? Explain with an example.

Heat is a form of energy that transfers from one object or substance to another because of a temperature difference. It always flows from a hotter object to a cooler one until both reach the same temperature (thermal equilibrium).

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Example of Heat

Imagine you hold a warm cup of coffee. The heat energy from the hot coffee transfers to your cooler hands. You feel the warmth because heat is moving from the coffee (hotter) to your hands (cooler).

What is Temperature?

Temperature is a measure of how hot or cold an object is. 

Examples of Temperature

1. Ice cube: It has a low temperature (cold).
2. Boiling water: It has a high temperature (hot).

Write difference between heat and temperature.

Difference between heat and temperature:

Heat	Temperature
Heat is the energy that moves from a hot object to a cold one.	Temperature tells us how hot or cold something is.
Measured in joules (J) or calories.	Measured in degrees Celsius (°C), Fahrenheit (°F), or Kelvin (K).
Depends on the amount of substance and how much energy it has.	Does not depend on the amount of substance.
Example: Heat from the sun warms your skin.	Example: The temperature outside is 30°C.

Book Exercises

Book work: 

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I. OBJECTIVE TYPE QUESTIONS
A. Choose the correct answer.
1. (c)
2. (a)
3. (d)
4. (a)
5. (a)
6. (a)

B. Fill in the blanks.
1. clinical
2. Celsius
3. 53 K
4. Celsius

C. State True or False. Also correct the false statements.
1. False, a laboratory thermometer cannot be used to measure the body temperature of humans.
2. False, the range of temperature that can be measured by using clinical thermometer is 35°C to 43°C.
3. False, normal temperature of the human body is 37°C.
4. True

Notebook work:

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D. Tick (√) the odd-one out giving reason.

1. Joule, others are temperature scales.
2. 37K, others denote average body temperature.
3. 100°C, others are associated with thermometer.
4. 100 J, others are measure temperature.

II. LOGIC BASED QUESTIONS

Short and Long Answer

1. The temperature where Fahrenheit and Celsius are the same is (– 40) i.e., – 40°F = – 40°C.

2. Bittu (35.8°C) : Room temperature (36.1°C) is higher than Bittu’s body temperature. Hence, Bittu will not feel cold; instead, he might feel slightly warm.

Mintu (36.2°C) : Room temperature (36.1°C) is slightly lower than Mintu’s body temperature. Mintu may feel cold as heat will leave his body to the cooler surroundings.

Chintu (36.4°C) : Room temperature (36.1°C) is lower than Chintu’s body temperature. Chintu will also feel cold due to the same heat loss from his body.

3. When Avi and Sheetal shake hands, since Sheetal’s palms are warmer than Avi’s, Avi will feel Sheetal’s palm as warm because her palm temperature is higher than hers. And Sheetal will feel Avi’s palm as cold because Avi’s palm temperature is lower than hers.

4. Since the boiling water is much hotter than the chapati, the chapati may feel “cooler” by comparison. However, this does not mean the chapati is actually cold—it is just cooler relative to the boiling water. 

5. This is done to ensure that the mercury thread (or the liquid column, if it is an alcohol thermometer) is reset to the lower end of the thermometer’s scale.

6. The equation to convert degree Celsius to Fahrenheit is :

°F = (°C × 9/5) + 32

The +32 is to account for the fact that 0 degrees Celsius is equivalent to 32 degrees Fahrenheit.

Using this equation after removing +32, we can see that one degree Celsius equals 9/5 or 1.8 degrees Fahrenheit.

So the temperature of second system is 1.8°F.

7. The bulb of the thermometer contains a temperature-sensitive liquid (mercury or alcohol). If one holds the bulb,

heat from his /her hand can transfer to the liquid, causing it to expand and giving a falsely high reading.

8. Similarity : Both laboratory and clinical thermometers both are used to measure temperature.

Differences

Feature	Clinical Thermometer	Laboratory Thermometer
Purpose	Measures human body temperature.	Measures the temperature of substances/objects in a lab setting.
Temperature Range	Narrow range: typically 35°C to 42°C (95°F to 108°F).	Wide range: typically -10°C to 110°C or more.
Kink (Constriction)	Has a kink near the bulb to prevent the mercury level from falling on its own.	Does not have a kink, so the liquid level responds instantly to temperature changes.
Reading Method	Can be read after being removed from the heat source (the body).	Must be read while the bulb is still in contact with the substance being measured.
Resetting	Requires a sharp jerk to bring the mercury level down.	The liquid level falls naturally as it cools; no jerking needed.

III. HIGHER ORDER THINKING SKILLS

1. Using coloured water instead of mercury in a thermometer would impact its accuracy and sensitivity. Water expands and contracts more significantly with temperature changes compared to mercury, leading to less precise measurements.

2. Absolute temperature in Celsius is −273°C.

Hence, absolute temperature in Fahrenheit scale is approximately −460° F.