Heat Energy Basics

Heat Energy

• Heat energy is a form of energy that creates sensations of hot or cold.
• It involves the transfer of energy from hotter to cooler objects.
• Temperature measures the degree of hotness of an object.

Measuring Temperature

• Thermometers are devices used to measure temperature.

Clinical Thermometer

• Designed specifically for measuring human body temperature.
• Consists of a narrow glass tube with a mercury bulb.
• Utilizes the Celsius scale (°C), normal body temperature is 37°C.
• The measurement range is between 35°C and 42°C.
• Usage involves placing the bulb under the tongue for a minute.
• Digital thermometers are becoming popular due to safety concerns with mercury.

Maximum-Minimum Thermometers

• Measures the highest and lowest temperatures over a given time period.
• Features a U-shaped glass tube to record temperature fluctuations.

Laboratory Thermometer

• Used for measuring temperatures of substances other than the human body.
• Comprises a long glass tube without kinks and a mercury bulb.
• Temperature range is from -10°C to 110°C, used for boiling and freezing point checks.

Transfer of Heat

• Heat transfers from hotter objects to cooler objects.

Conduction

• Heat transfer occurs through direct contact from hot to cold parts of an object.
• Conductors (e.g. iron, copper) allow heat to pass, while insulators (e.g. wood, plastic) prevent heat transfer.

Convection

• Heat transfer in liquids and gases occurs through the movement of heated molecules.
• Example: In boiling water, hot molecules rise and are replaced by cooler ones.
• Sea breeze occurs when land heats faster than the sea, causing cool air from the sea to flow inland.
• Land breeze happens at night when land cools faster than sea, causing cool air from land to flow to the sea.

Radiation

• Heat is transferred without a medium (e.g. air, liquid).
• Example: Heat from the sun or a hot object cooling in the environment.
• All hot bodies are capable of radiating heat.

Absorption of Heat

• Objects can reflect or absorb radiant heat.
• Dark colors absorb heat effectively, making them comfortable in winter.
• Light colors reflect heat, leading to comfort in summer.
• Wool is a poor conductor, providing insulation in winter climates.