Chapter 3: Energy What is energy? The Law of Conservation of Energy Energy Efficiency Thermal Energy Heat and Temperature

 Energy is the ability to do work or effect change.  Many different forms of energy exist.  From a variety of sources (sun, nuclear reactions, compressed elastic etc…) What is Energy?

 Kilajouuuleeeeees!!!!!!!!!  Energy is expressed in joules (j).  One joule corresponds to the energy required to move an object with the force of one newton (N) over a distance of one meter (m). 1 J = 1 N x 1 m Units of Energy

 1) Energy transfer: the movement of energy from one place to another.  e.g. Energy is transferred from hydroelectric power plants to our homes.  2) Energy transformation: the changing of energy from one form to another,  e.g. Mechanical energy from water turbines is transformed into electrical energy by a generator. Energy transfer and transformation

 The Law of Conservation of Energy states that energy can be neither created nor destroyed; it can only be transferred or transformed. The total amount of energy in an isolated system always remains constant. The Law of Conservation of Energy

Energy Efficiency

 Only 12% of the chemical energy from gasoline is actually used by the wheels to make the car move. Efficiency of Gasoline: chemical energy

 Thermal energy: the energy contained in a substance, determined by the number of particles in the substance and their temperature.  The particles in the substance move randomly and the more they are agitated the more they produce thermal (heat) energy.  Think of friction and rubbing your hands together, first slowly and then quickly – the more you agitate the particles in your hands, the hotter it gets  thermal energy. Thermal Energy

FactorFactor VariationResult Number of ParticlesMore particlesIncreased thermal energy Fewer particlesReduced thermal energy TemperatureHigh temperatureIncreased thermal energy Low temperatureReduced thermal energy Factors that affect thermal energy

 Thermal energy can be transferred from an environment where the temperature is high to an environment where the temperature is lower until the two environments have the same temperature. This transfer of thermal energy is known as heat.  Heat: the transfer of thermal energy between two environments with different temperatures. Heat always passes from the warmer to the cooler environment. Heat

The relationship between heat and thermal energy