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Chemistry
Chapter 2
18
Science
8th Grade
03/08/2012

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Term

CHEMICAL EQUATION

 

 

 

Definition

means: shows  a chemical reaction using symbols/formulas

 

ex: 1 C + 2 O = CO2

      2 H + 1 O = H2O

Term
REACTANT
Definition

means:  the substances at the beginning of a chemical equation



ex:  CaCO3      yields ------       CaO + CO2

      reactant -------------------     products

Term
PRODUCTS
Definition

means:  the new substances after the reaction is complete

 

 

ex:   CaCO3     yields ----------     CAO + O2

        reactant                              products

Term

OPEN SYSTEM

 

 

Definition

means:  matter can enter or escape to the surroundings

 

 

ex.:  a burning match releases oxygen in air

 

 

        a fire releases products (oxygen, gas, smoke) in air

Term
CONSERVATION
Definition

means:  during a chemical reaction, matter is is not created or destroyed.

 

 

ex:  conserve=save

****All atoms present at beginning of reaction are still there at end of reaction

Term
CLOSED SYSTEM
Definition

means:  matter is not allowed to enter or leave...it is contained

 

 

ex.:  a pear decaying under glass

      

        bacteria growing in a closed petri jar

Term
COEFFICIENT
Definition

means:  a number placed in front of chemical formula in an equation....used to balance equations


ex:  2 H2O + O2 -----  2 H2O

Term
SYNTHESIS
Definition

means:  put things together...2 or more elements or compounds combine = more complex substance

 

 

ex.:  H + O2 = Water

      hydrogen + oxygen = water

Term
DECOMPOSITION
Definition

means: breaks down the compounds into smaller products.....opposite of synthesis

 

ex.:  2 H202 ----- 2H20 + 02

  hydrogen peroxide ----- water + oxygen gas

Term
REPLACEMENT
Definition

means:  one element replaces another ...or...2 elements in 2 different compounds trade places

 

 

ex.:  2 Cu2O + C------- 4Cu + CO2

  the 2 oxygens were traded to the C to make CO2

Term
ACTIVATION ENERGY
Definition

means:  the amount of energy needed to start (activate) the chemical reaction

 

 

ex.:  electric spark ---activates (starts) the reaction between hydrogen and oxygen in water....

 

Term
CONCENTRATION
Definition

means:  the amount of substance in a given volume


ex:  Orange juice includes mostly water mixed with orange concentrate.....

       Orange juice concentrate is the solid form of just orange.  You have to add water to make it juice...

Term
CATALYST
Definition

means:  increases the rate of reaction (makes it happen faster)


ex:  heating up a mixture increases the rate of how fast it changes....so heat can be a catalyst....boiling water

Term
ENZYMES
Definition

means:  biological catalysts.....make chemical reactions necessary for life happen at a low temperature.


ex:  enzymes in your body break down the food you eat

Term
INHIBITORS
Definition

means:  decreases ( inhibits) the rate of reaction....prevent reactants from coming together

 

ex:  preservatives added to food slow down the reactions so food doesn't spoil

Term
COMBUSTION
Definition

means:  a rapid reaction between oxygen and a fuel that causes fire


ex:  when gas (fuel) + oxyegen + heat = FIRE

Term
FUEL
Definition

means:  a material that releases energy when it burns.

 

ex:  gas, oil, wood, paper

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