HOT AND COLD
Q. Write an example to show how our sense of touch can be misleading when comparing temperature?
Take three containers labeled A, B, and C. Put cold water in container A and hot water in container B. Mix cold and hot water in container C to make it lukewarm. Dip your left hand in container A and your right hand in container B for 2-3 minutes. Then put both hands in container C. The same water will feel warm to the left hand and cold to the right hand.
Q. What is temperature?
Temperature is a measure of how hot or cold an object is.
MEASURING TEMPERATURE
Q. What is a clinical thermometer?
A clinical thermometer is a special thermometer used to measure human body temperature.
Q. What are the different types of thermometers?
The main types of thermometers are clinical thermometer, laboratory thermometer, digital thermometer, and maximum-minimum thermometer.
Q. What is a Maximum-Minimum Thermometer?
A maximum-minimum thermometer is a special thermometer that measures the highest (maximum) and lowest (minimum) temperatures of a place during a day.
Q. Where is Maximum-Minimum Thermometer used?
Maximum-minimum thermometers are used in weather stations, meteorological departments, farms and gardens.
Q. Describe the structure of a clinical thermometer.
A clinical thermometer has a long narrow glass tube with a bulb at one end containing mercury. A shining mercury thread is visible outside the bulb along a temperature scale.
Q. Why is mercury used in clinical thermometers?
Mercury is used in thermometers because it expands uniformly with temperature, doesn't stick to glass, is clearly visible, and responds quickly to temperature changes.
Q. Why is there concern about mercury in thermometers?
There is concern because mercury is highly toxic and difficult to dispose of safely if the thermometer breaks.
Q. What is the kink in a clinical thermometer? What is its use?
The kink is a constriction in the mercury column that prevents mercury from falling back immediately after removal from the body, allowing temperature reading to be taken conveniently.
Q. What is meant by the range of a thermometer?
The range of a thermometer refers to the difference between the highest and lowest temperatures it can measure.
Q. What is the range of a clinical thermometer?
The range of a clinical thermometer is from 35°C to 42°C.
Q. Why does a clinical thermometer have a range of 35°C to 42°C?
This range is used because human body temperature normally stays between 35°C and 42°C.
Q. What is the range of a clinical thermometer in degrees Fahrenheit?
The range of a clinical thermometer in degrees Fahrenheit is from 94°F to 108°F.
Q. Which temperature scale is used in India?
In India, the Celsius scale (°C) is commonly used for temperature measurement.
Q. What is normal human body temperature?
The normal human body temperature is 37°C or 98.6°F.
Q. Is body temperature the same for every person?
No, body temperature may vary slightly from person to person.
Q. What precautions should be taken while using clinical thermometers?
1. It should not be used for objects other than human body
2. It should not be exposed to sun or flame
3. It should be washed before and after use
4. Ensure mercury is below 35°C before use
5. Reading should be taken at eye level
6. It should be handled carefully to avoid breakage
2. It should not be exposed to sun or flame
3. It should be washed before and after use
4. Ensure mercury is below 35°C before use
5. Reading should be taken at eye level
6. It should be handled carefully to avoid breakage
Q. What is the value of one small division on a clinical thermometer?
One small division on a clinical thermometer represents 0.2°C, with five small divisions between two bigger marks.
Q. Write the steps to read a clinical thermometer correctly.
1. Wash the thermometer with antiseptic solution
2. Shake it firmly to bring mercury below 35°C
3. Place the bulb under the tongue for 1 minute
4. Remove and hold horizontally at eye level
5. Read the mercury level without touching the bulb
2. Shake it firmly to bring mercury below 35°C
3. Place the bulb under the tongue for 1 minute
4. Remove and hold horizontally at eye level
5. Read the mercury level without touching the bulb
LABORATORY THERMOMETER
Q. What is a laboratory thermometer?
A laboratory thermometer is used to measure the temperature of various objects during scientific experiments.
Q. What is the range of a laboratory thermometer?
A laboratory thermometer typically has a range from -10°C to 110°C (approximately 14°F to 230°F).
Q. Write the temperature conversion formulas between Celsius and Fahrenheit scales.
°F = (9/5 × °C) + 32
°C = 5/9 × (°F - 32)
°C = 5/9 × (°F - 32)
Q. What precautions should be taken while using laboratory thermometers?
1. It should be kept upright during use
2. The bulb should be completely surrounded by the substance
3. The bulb shouldn't touch the container's surface
4. Reading should be taken while the thermometer is still in the substance
2. The bulb should be completely surrounded by the substance
3. The bulb shouldn't touch the container's surface
4. Reading should be taken while the thermometer is still in the substance
Q. Why can't a clinical thermometer be used to measure high temperatures?
A clinical thermometer cannot measure high temperatures because its limited range (35-42°C) would cause it to break at higher temperatures.
Q. Why does the mercury level change when the thermometer bulb touches objects?
The mercury level changes because heat causes mercury to expand (rise) or contract (fall) in response to temperature changes.
Q. What happens when you take a laboratory thermometer out of hot water?
The mercury level starts falling immediately as the thermometer cools down to room temperature.
Q. Write the steps to read a laboratory thermometer correctly.
1. Place the bulb completely in the substance
2. Wait for mercury to stabilize
3. Read while thermometer is still in the substance
4. Hold upright at eye level to read the temperature
2. Wait for mercury to stabilize
3. Read while thermometer is still in the substance
4. Hold upright at eye level to read the temperature
Q. What are the similarities between clinical and laboratory thermometers?
Both types of thermometers:
- Contain mercury
- Work on the principle of thermal expansion
- Have Celsius scale markings
- Are used to measure temperature
- Contain mercury
- Work on the principle of thermal expansion
- Have Celsius scale markings
- Are used to measure temperature
Q. What are the differences between clinical and laboratory thermometers?
Clinical thermometer:
- Has a kink in the capillary tube
- Has narrow range (35-42°C)
- Designed for human body only
Laboratory thermometer:
- Has no kink
- Has wide range (-10-110°C)
- Used for general laboratory purposes
- Has a kink in the capillary tube
- Has narrow range (35-42°C)
- Designed for human body only
Laboratory thermometer:
- Has no kink
- Has wide range (-10-110°C)
- Used for general laboratory purposes
Q. How does a digital thermometer work?
A digital thermometer uses electronic sensors to detect temperature changes and displays the reading digitally on a screen.
TRANSFER OF HEAT
Q. What is heat?
Heat is a form of energy that flows from hotter objects to colder objects.
Q. In which direction does heat always transfer?
Heat always flows spontaneously from hotter objects to colder objects.
Q. What will be the resulting temperature when one litre of water at 30°C is mixed with one litre of water at 50°C?
The resulting temperature will be 40°C (the average of the two temperatures).
Q. What are the three modes of heat transfer? Describe each mode and the medium required for it.
The three modes of heat transfer are:
1. Conduction: Requires direct contact through solids
2. Convection: Requires fluid medium (liquids/gases)
3. Radiation: Requires no medium (can transfer through vacuum)
1. Conduction: Requires direct contact through solids
2. Convection: Requires fluid medium (liquids/gases)
3. Radiation: Requires no medium (can transfer through vacuum)
Q. What are heat conductors?
Heat conductors are materials that allow heat to pass through them easily, such as metals.
Q. What are heat insulators?
Heat insulators are materials that resist heat flow, such as wood, plastic and wool.
Q. What is conduction?
Conduction is the transfer of heat through solids where particles vibrate and transfer energy to neighboring particles without changing position.
Q. What is convection?
Convection is heat transfer in fluids where heated particles move from hotter to cooler areas, creating circular currents that transfer heat.
Q. What is radiation?
Radiation is heat transfer through electromagnetic waves that can travel through empty space without any medium.
Q. Explain sea breeze.
Sea breeze occurs during daytime when land heats faster than sea. Warm air rises over land creating low pressure, causing cooler air from sea to flow toward land.
Q. Explain land breeze.
Land breeze occurs at night when land cools faster than sea. Warm air rises over sea creating low pressure, causing cooler air from land to flow toward sea.
Q. Why are ACs fitted at height?
ACs are fitted at height because cool air is heavier and settles down. This helps the cool air to spread in the whole room easily from top to bottom.
Q. Why are ventilators or exhaust fans fitted at the top?
Ventilators or exhaust fans are fitted at the top because hot air and smoke are lighter and rise up. They help remove this hot air and keep the room fresh.
KINDS OF CLOTHES WE WEAR
Q. Why do we wear light-colored clothes in summer and dark-colored clothes in winter?
We wear light-colored clothes in summer because they reflect heat, and dark-colored clothes in winter because they absorb more heat.
Q. Describe an experiment using two identical cans (one black and one white) containing equal amounts of water placed in sunlight. What result would you observe?
Water in the black can becomes warmer than in the white can because black surfaces absorb more heat radiation than white surfaces.
Q. Why do woolen clothes keep us warm in winter?
Woolen clothes keep us warm because wool fibers trap air (which is a poor heat conductor) between them, preventing body heat loss.
Q. Why do we prefer to wear cotton clothes in summer?
We wear cotton clothes in summer because cotton absorbs sweat easily and allows evaporation, which provides a cooling effect.
Q. Why does wearing more layers of clothing during winter keep us warmer than wearing just one thick piece of clothing?
Multiple layers trap more air (a good insulator) between them, reducing heat loss more effectively than a single thick layer.
Comments
Post a Comment