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Chapter 8 Chemical Reactions

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1 Chapter 8 Chemical Reactions

2 A chemical reaction is a process in which the physical and chemical properties of the original substances change as new substances with different physical and chemical properties are formed

3 Law of Conservation of Mass
During a chemical or physical change, all mass remains the same. Mass is neither created nor destroyed.

4 Parts of a chemical reaction
Subscript tells the # of atoms in molecule Coefficient tells # of molecules in reaction 2 H2 + O H2O coefficient coefficient subscript

5 Parts of a chemical equation
Reactant is what goes into a chemical reaction Product is what results in the reaction 2 H2 + O H2O product reactant reactant

6 The ease with which atoms will form bonds is its bonding capacity.
Capacity to react The ease with which atoms will form bonds is its bonding capacity. This capacity is directly related to the electrons and their placement and number within the energy levels.

7 What happens when a chemical reaction occurs?
Atoms can form molecules Molecules can break apart to form atoms Molecules can react with other molecules

8 Balancing Equations Start with the first atom on the reactants side
Count the total number of atoms of the element on left and then on the right Add a coefficient in front of atom(s) or compounds where necessary Never change a subscript Go back through each atom and recheck and/or change until # are equal on both sides of the equation

9 Types of Chemical Reactions
SYNTHESIS 2 or more substances combine DECOMPOSITION complex substance breaks down SINGLE - REPLACEMENT uncombined element replaces another element in a compound DOUBLE - REPLACEMENT atoms of 2 compounds replace each other (a flip-flop)

10 synthesis Simple molecules or compounds combine to make a new and more complex substance 2 H2 + O H2O

11 decomposition A complex substance breaks down into simpler substances 2 H2O H2 + O2

12 single-replacement 2Na + 2H2O 2NaOH + H2
Single element replaces another element within a compound 2Na + 2H2O NaOH + H2

13 double-replacement Different atoms in two different compounds replace each other MgCO3 + 2HCl MgCl2 + H2CO3

14 In any chemical reaction: some energy is needed to start the change some energy is involved during the reaction

15 ACTIVATION ENERGY is what is needed to get a reaction started
Ex: striking a match

16 Energy involved in the reaction can be either:
Exothermic or Endothermic

17 Exothermic ex means out therm means heat
energy is released during reaction the energy in the reactants are higher than the products Ex: fireworks

18 Endothermic endo means in therm means heat
energy is absorbed during reaction the energy in the products are higher than the reactants Ex: chemical ice

19 Kinetics is the study of reaction rates
In order to react, atoms must collide. In order for bonds to be broken, formed or reformed, particles must collide at precisely the correct angle with the proper amount of energy.

20 Four factors that influence the collision theory are . . .
Rates of Chemical Reactions The more collisions, the faster the rate of the chemical reaction Four factors that influence the collision theory are . . .

21 concentration surface area temperature catalysts
the amount of reactants present surface area amount of exposed material temperature higher temperature causes atoms to display more energy & reaction rate is increased catalysts increases speed by decreasing the activation energy needed, but does not enter the reaction called enzymes in living organisms

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