Temperature and Its Measurement Class 6 Science Chapter 7 NCERT Question Answer

Chapter 7: Temperature and Its Measurement

What is Temperature?

Temperature is a measure of the degree of hotness or coldness of an object. It indicates the thermal energy present in a substance. The SI unit of temperature is Kelvin (K), but it is also commonly measured in Celsius (°C) and Fahrenheit (°F).

Key Points:

It determines the direction of heat transfer (heat flows from a hotter body to a colder body).
Higher temperature means more kinetic energy in molecules, while lower temperature means less kinetic energy.

Measuring Temperature: Thermometer and Its Types

A thermometer is an instrument used to measure temperature. It consists of a temperature-sensitive material that expands or contracts with temperature changes.

Types of Thermometers:

Clinical Thermometer (Mercury/Alcohol-based)
- Used to measure body temperature.
- Has a narrow constriction (kink) that prevents mercury from falling back quickly.
- Temperature range: 35°C to 42°C.
Laboratory Thermometer
- Used in science experiments.
- No constriction like a clinical thermometer.
- Temperature range: -10°C to 110°C.
Digital Thermometer
- Uses electronic sensors to measure temperature.
- Displays temperature digitally.
- More accurate and safer than mercury thermometers.
Infrared Thermometer
- Measures temperature without direct contact.
- Commonly used in medical and industrial applications.
Maximum-Minimum Thermometer
- Used to record daily temperature variations.
- Used in weather forecasting and meteorology.
Gas Thermometer
- Measures temperature based on the expansion of gases.
- Used for highly precise scientific measurements.

Effects of Temperature on Substances

Temperature affects substances in several ways, such as:

Expansion and Contraction
- Most substances expand on heating and contract on cooling.
- Example: Railway tracks have expansion gaps to prevent bending due to heat.
Change of State
- Solid to liquid (Melting): Ice melts into water at 0°C.
- Liquid to gas (Evaporation): Water boils at 100°C to form steam.
- Gas to liquid (Condensation): Steam condenses into water on cooling.
- Liquid to solid (Freezing): Water freezes at 0°C.
Change in Density
- Heating causes substances to expand, decreasing their density.
- Example: Hot air rises due to lower density, forming wind currents.
Effect on Living Organisms
- Human body maintains a constant temperature of about 37°C.
- Extreme temperatures can cause heatstroke or hypothermia.

Applications of Temperature Measurement

Medical Field
- Clinical thermometers help diagnose fever and illnesses.
- Digital and infrared thermometers are widely used for quick and safe temperature readings.
Weather Forecasting
- Meteorologists use maximum-minimum thermometers to record temperature changes.
- Helps predict weather conditions and climate patterns.
Industrial Uses
- Thermometers are used in factories to monitor temperatures in chemical processes.
- Temperature control is essential in food preservation and processing industries.
Household Uses
- Thermostats in air conditioners and refrigerators maintain desired temperatures.
- Cooking thermometers ensure food is cooked at safe temperatures.
Scientific Research
- Precise thermometers are used in laboratories to conduct experiments.
- Gas thermometers help measure extremely high and low temperatures.

Summary

Temperature is a measure of heat energy and is measured using different types of thermometers.
Clinical and laboratory thermometers are common for medical and experimental use.
Temperature changes cause expansion, change of state, and density variations in substances.
Applications include medicine, weather forecasting, industries, households, and scientific research.

Understanding temperature and its measurement helps us make informed decisions in daily life, from checking our body temperature to predicting the weather and improving industrial processes.