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Practice Class 7 Science MCQs on heat, temperature, conductors and insulators, sea breeze, laboratory thermometer, and heat transfer with detailed explanations, real-life examples, NCERT concepts, and exam-oriented facts.
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Q1. The normal temperature of a healthy human body is:
Correct Answer: 37°C
Detailed Explanation:
The normal temperature of a healthy human body is approximately 37°C (98.6°F). This temperature is considered ideal because it allows the body’s organs, tissues, enzymes, and biological processes to function efficiently. The human body continuously produces heat through metabolic activities, and it also loses heat to the surroundings. The balance between heat production and heat loss helps maintain a stable body temperature.
The human body has a natural temperature-regulating system controlled by the brain, specifically the hypothalamus. This system ensures that the body temperature remains close to 37°C despite changes in weather or physical activity. When the body becomes too hot, sweating helps cool it down. When the body becomes too cold, shivering generates additional heat.
Body temperature may vary slightly throughout the day. It is usually lower in the early morning and slightly higher in the evening. Physical exercise, illness, and environmental conditions can also affect body temperature temporarily.
Doctors use clinical thermometers to measure body temperature. If the temperature rises significantly above 37°C, it may indicate fever, which often occurs when the body is fighting infections. Maintaining a normal body temperature is essential for good health and proper functioning of body systems.
Understanding body temperature helps students learn about heat, health, and the body’s ability to maintain internal balance.
Real-Life Examples:
- A doctor checks body temperature during illness.
- Fever causes body temperature to rise above normal.
- Sweating helps maintain normal body temperature on hot days.
Important NCERT Points:
- Normal human body temperature is 37°C.
- Body temperature is measured using a clinical thermometer.
- The body regulates temperature naturally.
- Fever indicates an increase in body temperature.
Exam-Oriented Fact:
37°C is equal to approximately 98.6°F.
Quick Revision Line:
The normal temperature of a healthy human body is 37°C.
Q2. Materials which allow heat to pass through them easily are:
Correct Answer: Conductors
Detailed Explanation:
Materials that allow heat to pass through them easily are called conductors of heat. These substances transfer heat quickly from one part to another because their particles and electrons can carry thermal energy efficiently. Metals are generally the best conductors of heat.
Common examples of conductors include copper, aluminum, iron, silver, and steel. Because of their excellent heat-conducting properties, these materials are widely used in cooking utensils, electrical appliances, and industrial equipment.
When one end of a metal rod is heated, the heat travels through the rod and eventually reaches the other end. This process is known as conduction. Heat always moves from a hotter region to a colder region until thermal balance is achieved.
In contrast, materials that do not allow heat to pass through easily are called insulators. Wood, plastic, rubber, cork, and wool are common insulators. These materials are used where heat transfer needs to be reduced or prevented.
The concept of conductors is important in everyday life. Cooking vessels are made from metals because they transfer heat efficiently. Similarly, radiators, heat exchangers, and many household appliances use conducting materials for effective heat transfer.
Learning about conductors and insulators helps students understand how heat moves and why different materials are chosen for specific purposes.
Real-Life Examples:
- Copper utensils heat food quickly.
- Iron pans conduct heat efficiently while cooking.
- Aluminum cookware is widely used in kitchens.
Important NCERT Points:
- Metals are good conductors of heat.
- Heat travels through conductors by conduction.
- Copper and aluminum are excellent conductors.
- Conductors are used in cooking utensils.
Exam-Oriented Fact:
Silver is one of the best conductors of heat and electricity.
Quick Revision Line:
Conductors are materials that allow heat to pass through them easily.
Q3. Sea breeze blows during:
Correct Answer: Day
Detailed Explanation:
Sea breeze is a local wind that blows from the sea towards the land during the daytime. It occurs because land and water heat up at different rates when exposed to sunlight. Land absorbs heat more quickly than water, causing the air above the land to become warmer.
As the warm air over the land rises, it creates a low-pressure area. The cooler air above the sea then moves toward the land to replace the rising warm air. This movement of cool air from the sea to the land is called sea breeze.
Sea breeze is usually strongest during the afternoon when the temperature difference between land and sea is greatest. It helps cool coastal regions and makes the climate more comfortable. People living near beaches often experience cooler temperatures because of sea breeze.
At night, the situation reverses. Land cools faster than water, causing the air above the sea to remain warmer. As a result, wind blows from land toward the sea, which is called land breeze.
Sea breeze plays an important role in weather patterns, coastal climates, and temperature regulation. It demonstrates how differences in heating affect air movement and atmospheric pressure.
This topic helps students understand the relationship between heat, air pressure, and wind formation.
Real-Life Examples:
- Cool winds are often felt at beaches during the afternoon.
- Coastal cities experience sea breeze regularly.
- Sea breeze provides natural cooling in hot weather.
Important NCERT Points:
- Sea breeze blows during the day.
- Land heats faster than water.
- Warm air rises over land.
- Cool air moves from sea to land.
Exam-Oriented Fact:
Sea breeze is caused by unequal heating of land and water.
Quick Revision Line:
Sea breeze is a daytime wind that blows from the sea toward the land.
Q4. A laboratory thermometer generally has a range from:
Correct Answer: (-10°C to 110°C)
Detailed Explanation:
A laboratory thermometer is an instrument used to measure the temperature of substances and experimental materials in laboratories. Unlike a clinical thermometer, which is designed only for measuring human body temperature, a laboratory thermometer can measure a much wider range of temperatures.
The usual range of a laboratory thermometer is from -10°C to 110°C. This wide range makes it suitable for scientific experiments involving liquids, solids, and gases. Students commonly use laboratory thermometers during practical activities involving heating and cooling.
A laboratory thermometer consists of a glass tube containing a liquid such as mercury or colored alcohol. As temperature changes, the liquid expands or contracts, causing the level to rise or fall inside the tube. The temperature can then be read from the calibrated scale.
Unlike clinical thermometers, laboratory thermometers do not have a kink in the capillary tube. Therefore, they must be read while still immersed in the substance being measured.
Laboratory thermometers are important tools in science because accurate temperature measurement helps ensure reliable experimental results. Understanding how these thermometers work helps students develop practical laboratory skills.
Temperature measurement is used in chemistry, physics, biology, weather observation, and many industrial processes.
Real-Life Examples:
- Measuring the temperature of heated water in experiments.
- Checking temperatures during laboratory activities.
- Scientific research involving temperature observations.
Important NCERT Points:
- Laboratory thermometer range is -10°C to 110°C.
- Used for scientific experiments.
- Must be read while immersed in the substance.
- Has no kink unlike a clinical thermometer.
Exam-Oriented Fact:
A clinical thermometer usually measures only human body temperatures, while a laboratory thermometer covers a wider range.
Quick Revision Line:
A laboratory thermometer generally measures temperatures from -10°C to 110°C.
Q5. Stainless steel pans are usually provided with copper bottoms because:
Correct Answer: Copper is a better conductor of heat
Detailed Explanation:
Stainless steel pans are often manufactured with copper bottoms because copper is an excellent conductor of heat. Heat conduction refers to the transfer of thermal energy from one part of a material to another. Copper transfers heat much faster and more evenly than stainless steel.
If a cooking pan were made entirely of stainless steel, heat would spread slowly and unevenly, causing some areas to become hotter than others. By adding a copper base, heat from the stove is distributed uniformly across the bottom of the pan. This results in more efficient cooking and reduces the chances of food burning.
Copper also responds quickly to temperature changes. When the heat source is increased or decreased, copper adjusts rapidly, giving better control during cooking. However, copper alone can react with certain foods and may require special care. Therefore, manufacturers combine the strength and durability of stainless steel with the excellent heat-conducting properties of copper.
This combination creates cookware that is durable, hygienic, and highly efficient. The principle behind copper-bottom utensils demonstrates the practical application of heat conduction in everyday life.
Understanding why different materials are used in cookware helps students connect scientific concepts with real-world applications.
Real-Life Examples:
- Copper-bottom utensils are commonly used in kitchens.
- Professional chefs often prefer cookware with copper layers.
- Even heating helps prevent food from burning.
Important NCERT Points:
- Copper is a very good conductor of heat.
- Stainless steel is durable but less conductive.
- Copper distributes heat uniformly.
- Copper-bottom pans improve cooking efficiency.
Exam-Oriented Fact:
Copper conducts heat much better than stainless steel.
Quick Revision Line:
Copper bottoms are used in stainless steel pans because copper is an excellent conductor of heat.
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