16-1: Chemical Changes in Matter
- In a chemical reactions, the reactants are changed
into the products, which are different substances.
- According to the law of conservation of mass, the mass
of the reactants in a chemical reaction equals the mass of the products.
- A chemical equation is a shorthand way of describing
a chemical reaction using symbols, coefficients, and formulas.
16-2: Chemical Reactions – Up in the Air
- The ozone layer helps protect Earth by absorbing ultraviolet
radiation from the sun.
- In the upper atmosphere, CFCs (chlorofluorocarbons)
release atoms of chlorine that destroy ozone molecules.
- Replacing CFCs and regulating their use may slow down
the loss of ozone.
16-3: Chemical Equations
- A balanced chemical equation has the same number of
atoms of each element on both sides of the equation.
- The final step in the process of balancing a chemical
equation is the choice of the correct coefficients.
16-4: Types of Chemical Reactions
- Many specific chemical reactions can be classified
as one of four reaction types – synthesis, decomposition, single-displacement,
and double-replacement.
- In a synthesis reaction, two or more substances combine
to form another substance.
- In a decomposition reaction, one substance breaks down
into two or more simpler substances.
- In a single-displacement reaction, one element replaces
another in a compound.
- In a double-displacement reaction, two elements switch
places.
16-5: Energy and Chemical Reactions
- In an exothermic reaction, energy is released.
- In an endothermic reaction, energy is absorbed.
- A catalyst is a substance that speeds up a chemical
reaction without itself being permanently changed. |
