Changes in Matter 2 chemical changes occurs when

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Changes in Matter 2) chemical changes- occurs when bonds break between atoms and form

Changes in Matter 2) chemical changes- occurs when bonds break between atoms and form new substances. synthesis decomposition burning oxidation chemical changes occur as a result of a chemical reaction!

chemical reaction- process in which substances break bonds between atoms and form new substances.

chemical reaction- process in which substances break bonds between atoms and form new substances. Na. OH + HCl + H Cl Na. Cl + HOH

Na. OH + reactants HCl Na. Cl yields + HOH products what goes in

Na. OH + reactants HCl Na. Cl yields + HOH products what goes in must come out! Law of Conservation of Matter The total number of atoms in a reaction remains constant; the total number of atoms of an element before a reaction equals the total number of atoms of an element after a reaction.

H 2 H H + + O O O 2 H 2 O ?

H 2 H H + + O O O 2 H 2 O ?

this equation needs to be balanced. 2 H 2 coefficient + O 2 2

this equation needs to be balanced. 2 H 2 coefficient + O 2 2 H 2 O coefficient- a number that is placed in front of a chemical formula in a chemical equation and tells how many molecules of that substance are involved in the reaction.

2 H H O + O 2 2 H 2 O

2 H H O + O 2 2 H 2 O

Balancing Chemical Equations 1) Divide the equation into reactants and products. H 2 +

Balancing Chemical Equations 1) Divide the equation into reactants and products. H 2 + O 2 H 2 O

2) List the elements on both sides of the equation in the same order.

2) List the elements on both sides of the equation in the same order. H 2 + H 2 O O 2 H H O O

3) Count the atoms of each element on both sides of the equation. O

3) Count the atoms of each element on both sides of the equation. O 2 H 2 O H 2 + H =2 O =1

4) Add a coefficient in front of the formula and recount the atoms on

4) Add a coefficient in front of the formula and recount the atoms on both sides of the equation. O 2 2 H 2 O H 2 + H =2 2 H =4 O =2 1

5) Continue to add coefficients in front of the formulas until there is an

5) Continue to add coefficients in front of the formulas until there is an equal number of atoms on both sides of the equation. 2 H 2 + O 2 2 H 2 O H =4 2 H =4 O =2

Types of Chemical Reactions 1) synthesis- when 2 or more simple reactants combine to

Types of Chemical Reactions 1) synthesis- when 2 or more simple reactants combine to create a more complex product. SO 3 + H 2 O H 2 SO 4 2) decomposition- when a large, complex reactant breaks down into 2 or more smaller products. 2 Al 2 O 3 4 Al + 3 O 2

3) single replacement- when one element replaces another to form a new product. 2

3) single replacement- when one element replaces another to form a new product. 2 Fe 2 O 3 + 3 C 4 Fe + 3 CO 2 4) double replacement- when two elements in different reactants replace each other to form 2 new products. 2 Ag. NO 3 + H 2 S Ag 2 S + 2 HNO 3

Reactions & Energy endothermic reactions- chemical reactions that absorb energy; feels cold. exothermic reactions-

Reactions & Energy endothermic reactions- chemical reactions that absorb energy; feels cold. exothermic reactions- chemical reactions that release energy (light &/or heat); feels warm.