What is What is WorkWork??

When movement occurs against a restraining force

Work = Force X Distance

Energy is the capacity to do work

Units of EnergyUnits of Energy

Joule

1 Joule = Energy required to raise a mass of

1 Kg to a height of 10 cm against

gravity

or

Energy required for each heart beat

Units of EnergyUnits of EnergyCalorie

1 Calorie (cal)

Energy required to raise the temperature

of 1 gram of water by 1Co

1 Kilocalorie (Kcal) = 1000 calories

1 Kilojoule (kJ) = 1000 joules

Energy is conserved…Energy is conserved…

Law of Conservation of Energy

(First Law of Thermodynamics)

Energy is neither created or destroyed

It is transformed as it is transferred

The energy of the universe is constant

Chemical EnergyChemical EnergyExothermic Reaction

When energy is released at the end of the reaction

(expressed as a negative number)Endothermic Reaction

When energy is absorbed at the end of the reaction

(expressed as a positive number)

Which is a better fuel?Which is a better fuel?

PropaneCombustion releases –2016 kJ/mole

Ethyl alcoholCombustion releases –1250 kJ/mole

But there are other considerations…