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 CO2 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 cal 4.184 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