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chem lecture 3

# chem lecture 3 - Matter and energy are components of the...

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Matter and energy are components of the universe. Section 1.6 Matter: physical objects that take up space and have mass atoms, elements, molecules, compounds Energy: the capacity to do work potential, kinetic (thermal, electrical, nuclear) kinetic energy = 1 / 2 mv 2 m = mass (kg) v = velocity (m/s) KE = kg × m 2 /s 2 = Joule most familiar with kinetic energy, the energy of motion Ex. Calculate the KE of a 5 kg ball traveling at 5 m/s. ( 1 / 2 )(5 kg)(5 m/s) 2 = ( 1 / 2 )(5)(25) J = ( 1 / 2 )(125) J= 62.5 J Chemicals also contain POTENTIAL energy Potential energy is stored energy. Chemicals store this energy in bonds and intermolecular forces. Examples of potential energy: • a truck on a hill • a stretched rubber band • a stick of dynamite Each can be converted into kinetic energy low potential energy high potential energy Section 1.6 Definition of spontaneous Spontaneous reactions release energy as the substances move from a higher energy to a lower energy state. Section 1.6 Which occurs spontaneously? A floppy rubber band becomes taut E final E initial E final E initial A taut rubber band becomes floppy OR Definition of spontaneous E = E final - E initial Section 1.6 E final E initial E final E initial Spontaneous Non-spontaneous E = E final - E initial Energy In E > 0 Energy Out E = E final - E initial E < 0 Systems in nature seek the lowest energy Section 1.6 What is What is E? E i = = - 2 kJ E f = = - 10 kJ 10 kJ Is this change spontaneous or non Is this change spontaneous or non- spontaneous ? Definition of spontaneous Spontaneous reactions release energy as the substances move from a higher energy to a lower energy state. E < 0 = E final - E initial Section 1.7 Potential Energy and Charged Particles Chemicals store potential energy in bonds, intermolecular forces, and within the atom.

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