Rabu, 24 Agustus 2011

Pengenalan Kimia

Look at the world around us. The world we have built depends on our use of energy. The cars we drive, the electricity that powers our lights and machines, the dynamite we use in construction, and the way we heat our homes, all depend on our efficient use of energy. The way we use this energy is therefore very important to us. Two aspects of energy use should be considered.
a) Sources of energy we use.
b) The technologies we have created to use the sources of energy efficiently.
burning house
a) A Study of Energy Sources
Click on the flame and complete the jigsaw relating to energy sources

lightning bolt (electricity)
b) Uses of Energy
Click on the picture of lightning and complete an assignment on the technologies we have developed to utilize energy
Basic Questions about reactions and energy
Most of the energy we use today still comes from a chemical source. Since the production and use of energy is so important, we need to perform a careful study of energy changes associated with chemical reactions. Let's start by considering some basic questions.
1) What types of reactions occur in terms of energy?
2) Why causes a chemical reaction to take place?
3) Why do some reaction release energy and some absorb it?
4) What happens to the chemical substances at the molecular level when reactions release energy, or absorb energy?
1) What types of reactions occur in terms of energy?
to answer this question complete Activity #1 below
burning house
Click on picture
Activity #1
Concept Attainment: Types of Reactions

Why do Chemical Reactions occur?
Chemists have determined that chemical processes will occur spontaneously for two main reasons:
burning match
I) Chemical reactions occur because the products of the reaction have less energy than the reactants. (Drive toward less energy). These reactions release energy into the environment, like the burning of a match.
Click on the picture to further examine energy changes in reactions

II) Chemical reactions also occur because the products are more random (less ordered) than the reactant . (Drive toward greater entropy)
Click on the picture to further examine entropy changes in reactions.

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