Chemical Energy

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Chemical Energy

• Fuel for Life

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What is Chemical Energy?

• Chemical energy is the energy that is stored in
  the chemical composition of matter.
• An example is the energy used by cells in your
  body come from the chemical energy in the food
  you eat.
• Energy is released as the chemical compounds are
  broken apart.

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Compounds
Chemical Energy
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What is a Chemical Element?

• A chemical element is the simplest form of a
  substance (matter).
• If a chemical element is broken down it becomes
  protons, neutrons and electrons (an atom).
• Chemical elements make up all the things in the
  physical world around us.
• Chemical elements are listed in the Periodic
  Table of the Elements
• Chemical elements combine to form molecules and
  compounds.

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What is an Atom?

• Atoms are collections of tiny bits of
  electricity, which we call protons, neutrons and
  electrons .
• When atoms come together to form larger clumps
  they are known as molecules.
• A molecule is a group of two or more atoms that
  stick together.
• Example O2, which is an oxygen
• molecule made from two atoms of oxygen.

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What is a Chemical Compound?

• A chemical compound is the combination of one or
  more elements.
• Example H2O, which is water made from two atoms
  of hydrogen and one atom of oxygen.
• Chemical compounds can not easily be separated.

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Mixtures and Solutions

• A mixture is the combination of substances that
  are not chemically combined.
• A mixture can easily be separated (taken apart)
  using physical means.
• Example Sand and iron mixture.
• A solution is the combination of substances in
  liquid form. A solution is like a liquid
  mixture.
• Solutions are not chemically combined so they can
  easily be separated.
• Example Salt dissolved in water.
• Solutions can be acidic, or basic, or neutral.
• This characteristic of solutions is called pH.

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What is pH?

• Every liquid you see will probably have either
  acidic or basic traits.
• Scientists use something called the pH scale to
  measure how acidic or basic a liquid is.
• pH stands for potential Hydrogen.
• The pH of solutions are measured on a scale of 0
  to 14.
• 0 being the most acidic
• 14 being the most basic
• A value of 7 is considered neutral and is
  neither acidic or
• basic.
• Examples
• stomach acid pH of 2.5 distilled water
  pH of 7
• Soda ash pH of 11

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pH Scale
Distilled Water
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What is a Physical Change?
The way something looks.

• A physical change is a change in a substance
  where nothing new is created, (it does not change
  the chemical make up of the substance).
• Example Ice melts to water (both are still H2O).
  
• Physical changes are usually changes in phase, or
  state of matter.

Solid
The way the water looks (state of matter) is
changing, but it is still water!
Liquid
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What is a Chemical Change?

• A chemical change is a ..
• change that does create something new, (a new
  chemical make up results).
• Example When iron rusts. The iron (Fe) becomes
  iron-oxide (Fe2O3).
• Chemical changes occur when elements recombine
  with other elements, or in different
  combinations.
• Chemical changes occur during chemical reactions.

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Exothermic vs Endothermic

• Chemical reactions often involve heat and can be
  either exothermic or endothermic.
• Exothermic chemical reactions give off heat.
  (feel hot)
• Endothermic chemical reactions take in heat.
  (feel cool)

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