Slides-Heating and Cooling

Hot and Cold

• Heat and Temperature
• Temperature tell us how hot something is. We use a thermometer to measure the temperature. Heat is form of energy.
• Heat Flow
• Heat always form a hotter to a older object. So the hotter object cools down the cooler object to warm up.
• Excited particles
• When you heat you transfer energy to its particles and move faster. In a solid they vibrate more. In liquids and gases they move around more faster. It means temperature increases.

Thermal Conduction

• Thermal conduction and Insulation
• The heat passes through the saucepan from the gas flame by conduction. Conduction is the way that heat is transferred in a solid. Many non-metals such as paper, cloth, wood and plastic are bad conductors of heat. We say there are thermal insulators.
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Convection

• How does the heat energy is transferred in liquids and gases?
• The heat energy can transferred in liquids and gases by convection, which is the rising warm air through colder air is called convection.
• Convection currents and their uses
• We use convection currents a lot in everyday life. An electric kettle relies on convection currents to heat all the water inside it.

Radiation

• Infrared Radiation
• This picture is a thermogram of an elephant. It shows temperature on the surfaces. The temperature scale is coloured, from dark blue (coldest) though red to white( warmest). We can see the temperature of the elephant because hot objects give off infrared radiation.
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Conserving Energy

• Reducing Heat loss
• Transfer of heat energy can happen by conduction, convection and radiation, and often all three together.
• Conserving Energy
• A light bulb transfers energy from electricity to light. But the bulb gets hot, so some energy is also transferred to heat, which transfers to air. This is wasted energy. it can not be used again
• Total energy input=total energy output