7th Class Science - Chapter 4: Heat

Heat

• Heat is a form of energy that involves a shift of energy from a hotter to a cooler object.
• Hot and cold can be differentiated based on the differences in their temperatures.

Measuring Temperature

• A thermometer is a device used to measure temperature.
• Clinical thermometer is used to measure body temperature, usually in the range of 35°C to 42°C, and is widely used in hospitals and at home.
• Clinical thermometer consists of a long, narrow glass tube with a bulb that contains mercury at one end.
• Digital thermometers are favored nowadays because they don't contain mercury and are less harmful.
• Maximum-Minimum Thermometers are used to calculate the daily minimum and maximum temperatures.
• Laboratory Thermometer is used to measure temperatures of all items other than human bodies, typically in the range of 10°C to 110°C.

Transfer of Heat

• Heat is the transmission of energy from a hotter commodity to a cooler commodity.
• Heat transfer can take place in various ways, including conduction and convection.

Conduction

• Conduction is a procedure of heat transfer where the heat is transmitted from the hot section to the cold section of the articles.
• Examples of conductors include iron and copper.
• Examples of insulators or poor conductors include wood and plastic.
• Handles of most utensils are made of plastic or wood because they are insulators.

Convection

• Convection is a way of heat transfer in liquids and gases, where the heat is transmitted by the shifting of the heated molecules in them.
• Examples of convection include when bubbles rise to the top from the bottom of a vessel while boiling water.
• Convection is the concept behind the interesting characteristics found in the coastal areas, termed the sea and land breeze.