The Dance of the Elements: Simple Chemical Reactions

5 types of reactions 1.Synthesis (S) 2.Decomposition (D) 3.Single replacement (SR) 4.Double replacement (DR) 5.Combustion (C)

Visualizing chemical reactions is much like imagining the elements involved in a simple dance. At a dance, people can pick a partner, separate and take a break, change a dance partner or change both dance partners.

At the beginning of a dance, partners join together. When elements combine to form a new compound, this is called a SYNTHESIS REACTION.

Synthesis Reactions Elements combine to form a new compound that has different properties than the elements alone. Synthesis means “to make” and what happens in this reaction is that smaller parts create a new more complex compound. Reaction

Recognizing a Synthesis Reaction All synthesis reactions follow the pattern A + B  AB Looking at a real reaction, like one below, two or more different elements/compounds combine to form one new compound 2Na (s) + Cl 2 (g)  2NaCl (s)

There comes a time for partners to stop dancing and take a break. When chemical compounds divide and break down into smaller components, this is called a DECOMPOSITION REACTION.

Decomposition Reactions Decomposition occurs when a compound breaks down from a complex molecule into simpler substances. Decomposition means “to break down” or “decay.”

Recognizing a Decomposition Reaction All decomposition reactions follow the pattern AB  A + B In an actual reaction, one larger compound breaks down into two or more smaller substances. HgCl 2 (s)  Hg (l) + Cl 2 (g)

Dancers sometimes change partners When chemical compounds change one partner for another, this is called a SINGLE DISPLACEMENT REACTION.

Single Displacement Reactions In this reaction, a more reactive ion replaces a less reactive ion and a new compound is produced. Reaction

Recognizing a Single Displacement Reaction This reaction follows the pattern AB + C  AC + B An actual single displacement reaction would free one ion and take up another ion Mg (s) + 2 H 2 O (l)  Mg(OH) 2 (l) + H 2 (g)

Dancers can also change both partners When two chemical compounds both exchange a partner, it is called a DOUBLE DISPLACEMENT REACTION.

Double Displacement Reactions Reaction In this reaction, the more reactive ions pair to form a new compound and the less reactive pair also form a new compound.

Recognizing a Double Displacement Reaction This reaction follows the pattern AB + CD  AD + CB A double displacement reaction would free ions to change partners AgNO 3 (aq) + KCl (aq)  AgCl (s) + KNO 3 (aq)

It’s that simple! Chemistry isn’t always difficult. By learning to recognize the four simplest types of chemical reactions, you have taken a big step towards learning how different chemicals interact with one another.

HOMEWORK READ lab CAREFULLY!!!! HANDOUT: front : tell type for 1—6, 8—14 Back : tell type for 1—15 Finish ch. 8 reading guide AND webquest for a late grade!! BE READY FOR QUIZ ON TYPES OF REACTIONS NEXT CLASS PERIOD!!

tch?v=JQVl1-RDFWI (you tube: types of chemical reactions intro.wmv)