Thermal Energy & Heat Heat and Its Uses

Thermal Energy & Heat 16.1 Thermal Energy and Matter

THERMAL ENERGY & MATTER: Journal 1. In which direction does heat flow spontaneously? 2. Define TEMPERATURE 3. How is THERMAL ENERGY transferred? 4. What are the factors that determine the THERMAL ENERGY of a material? 5. Which type of material heats more, one with a high specific heat, or one with a low specific heat? 6. Is WORK 100% efficient? How do you know?

THERMAL ENERGY & MATTER Work and Heat- work is never 100% efficient. Some is always lost to heat.

Heat- the transfer of thermal energy from one object to another because of a temperature difference. In what direction does heat flow spontaneously? FROM HOT to COLD

Temperature = measure of how hot or cold something is compared to a reference point. Temperature is the average kinetic energy of the particles in an object. In the image below, where is average kinetic energy greater? Higher temperature  

Heat flows DOWN the bar through COLLISIONS. Collisions transfer thermal energy from hot to cold.

Thermal energy- total potential and kinetic energy in an object. It depends on mass, temperature, and phase of an object. If both objects are in the same phase & at the same temperature, which one has MORE thermal energy?  Because there are MORE particles moving around.

Thermal expansion/contraction - change in volume of a material due to temperature change. Occurs because particles of matter collide more or less as temperature changes. Thermal expansion   Also, wrap on beaker and lava lamp

Specific Heat – amount of heat needed to raise ONE gram of a material ONE degree Celsius.

The LOWER a material’s specific heat the MORE its temperature rises when energy is added. Which will heat faster (has the lower specific heat)? Water? Or Lead? YES! Specific heat of water = 4.18 J/g°CSpecific heat of lead = 0.46J/g°C

Thermal Energy & Heat 16.2 Heat and Thermodynamics

HEAT TRANSFER What type of HEAT TRANSFER is occurring in the pictures? Conduction, convection or radiation? CONDUCTION – The transfer of thermal energy with no transfer of matter.

What type of HEAT TRANSFER is occurring in the pictures? Conduction, convection or radiation? CONVECTION – The transfer of thermal energy when particles of a liquid or gas move from one place to another

CONVECTION – in the earth and sun

HEAT TRANSFER What type of HEAT TRANSFER is occurring in the pictures? Conduction, convection or radiation? RADIATION – The transfer of thermal energy by waves moving through space. ALL OBJECTS radiate energy!

THERMODYNAMICS The study of conversions between thermal energy and other forms of energy.

THERMODYNAMICS First Law: Energy is Conserved

Thermal Energy & Heat 16.3 Using Heat

THERMAL ENERGY & MATTER: Journal 1. Define Convection, Conduction and Radiation 2. Give an example of each. 3. Write a sentence describing how each is important to our everyday lives. 4. How do we use heat in our everyday lives?

PART 2 - USING HEAT HEAT ENGINES The two main types of heat engines are External combustion and Internal Combustion External = power plants Internal = car engine

External combustion – produces electricity at power plants. Water is heated by a fuel and the pressurized steam spins a turbine.

HEAT ENGINES External combustion – nuclear power plants.

USING HEAT Internal combustion – car engines. The fuel (gas) is compressed and ignited (lit) to drive a piston.

Internal combustion – car engines. Four-stroke engine.