Physical Science 9 Chemical Reactions

Transcription

1 0803 Chapter 5.1 1

2 0803 Chapter 5.1 2

3 0803 Chapter 5.1 3

4 reactants products 0803 Chapter 5.1 4

5 0803 Chapter 5.1 5

6 A combustion reaction is one of five different types of chemical reactions. In a combustion reaction, oxygen is ALWAYS one of the reactants Chapter 5.1 6

7 If there is not enough oxygen available during combustion, the CO 2 is replaced with CO (Carbon monoxide). This is why it is very important that gas appliances remain clean and obstruction free so that enough oxygen can complete the combustion reaction Chapter 5.1 7

8 A decomposition reaction is another type of reaction. You can tell a decomposition reaction because there are more products than there are reactants (the reactant(s) are decomposing to form different substances Chapter 5.1 8

9 A combination or SYNTHESIS reaction reaction is a reaction where there are more reactants than there are products. The reactants are combining to form a compound Chapter 5.1 9

10 There are two other kinds of chemical reactions. The first is single-displacement. It is where one substance takes the place of another substance. CuCl 2 + Al AlCl 3 + Cu In the above reaction, Aluminum takes the place of Copper. A single-displacement reaction takes the form AB + C CB + A 0803 Chapter

11 The last type of reaction is a double-displacement reaction. This is where two elements switch places with each other. CuCl 2 + AlF 3 AlCl 3 + CuF 2 In the above reaction, Aluminum and Coppper switch places. A double-displacement reaction takes the form AB + CD CB + AD 0803 Chapter

12 Let s review the five types of reactions A + B AB Synthesis reaction AB A + B Decomposition reaction A + O B + CO Combustion reaction 0803 Chapter

13 Let s review the five types of reactions A single-displacement reaction takes the form AB + C CB + A A double-displacement reaction takes the form AB + CD CB + AD 0803 Chapter

14 The five reaction types just reviewed were discovered by earlier chemists, and these classifications are still used today. However, modern chemists have used a new classification using the knowledge we have learned about the transfer of electrons in a chemical reaction. These type of reactions are classified as RE-DOX reactions. In redox reactions, electrons are transferred from one reactant to another Chapter

15 Let s take a look at a chemical reaction that takes place everyday the rusting of iron. The chemical equation for this reaction is Fe + O 2 Fe 2 O 3 In this reaction, iron forms the iron ion Fe +3. In other words, iron LOSES three electrons in this reaction Chapter

16 Let s take a look at a chemical reaction that takes place everyday the rusting of iron. The chemical equation for this reaction is Fe + O 2 Fe 2 O 3 Oxygen GAINS two electrons to become Chapter

17 Iron loses electrons. Substances that LOSE electrons are said to be OXIDIZED. Metals are commonly oxidized. In other words, they LOSE electrons in chemical reactions. Oxygen gains electrons in this reaction. Substances that GAIN electrons are said to be REDUCED. The terms REDUCED and OXIDIZED are where the term REDOX reaction comes from Chapter

18 An easy way to remember this is by using a mnemonic: OIL RIG Oxidation Is the Loss of electrons. Reduction Is the Gain of electrons Chapter

19 Or. LEO says GER Loss of Electrons is Oxidation.. Gain of Electrons is Reduction Chapter

20 Radicals Radicals are fragments of molecules that have at least one electron available for bonding. Polymers are formed in reactions involving radicals Chapter

21 0803 Chapter

22 Done with 5.2! 0803 Chapter