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) + Cl2 (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.”
Reaction
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.
HgCl2 (s) Hg (l) + Cl2 (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 H2O (l) Mg(OH)2 (l) + H2 (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
AgNO3 (aq) + KCl (aq) AgCl (s) + KNO3 (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!!
http://www.youtube.com/watch?v=JQVl1-RDFWI
(you tube: types of chemical reactions intro.wmv)