The Flow of Energy-Heat Energy and Heat

Energy Energy is weightless, odorless, and tasteless Gasoline is an example of chemical potential energy Different substances store different amounts of energy

Energy Types of atoms and their arrangement in a substance also determines amount of stored energy

Heat Represented with q Only Changes caused by heat can be detected Heat always flows from warmer to cooler

Thermo Processes All chemical reactions and changes either release or absorb heat System is object of focus Surroundings are everything around object

Thermo Processes Direction of heat flow is given from point of view of the system Heat flowing into a system is positive q This is heat absorption- endothermic

Endothermic System gains heat from surroundings which are cooling

Exothermic Heat flows out of the system to surroundings- negative q Release of heat

Heat Capacity A calorie is amount of heat needed to raise 1 g of water 1 C Difference between calorie and Calorie Calorie is energy in food 1 Calorie is = 1000 calories

Heat Capacity 10 g of sugar has 41 Calories means 10 g of sugar releases 41,000 calories of heat when burned to make CO 2 and water 1 Joule is ¼ of a calorie 1J of heat raises the temp of 1g of water.239 C

Heat Capacity 1J =.239 cal4.184 J= 1 cal Heat capacity depends on mass and chemical composition Greater mass greater heat capacity Different chemical composition different heat capacity Pg.508 Table 17.1

Specific Heat Amount of heat it takes to raise 1g of substance 1 C Relation between heat capacity and specific heat –Heat capacity is = to specific heat X mass in grams. –q= m C ΔT

Specific Heat Used by farmers to protect their crops As water freezes it releases heat Equation pg.509