5.2 Decomposition of substances

• Scheikunde
• Middelbare school
• vwo
• Leerjaar 3

5.2 Decomposition of substances

Flashback

You know what you need for a combustion reaction

You know several methods how to extinguish a fire

You know which products can be formed with a combustion

You are able to make the balanced equation of a combustion

You can explain what is meant by a reagent

Explain which reagents are needed to identify the combustions products: water,carbondioxide and sulfurdioxide

You know the difference between a complete and an incomplete combustion

Flashback

Explain which reagents are needed to identify the combustions products: water,carbondioxide and sulfurdioxide

You know the difference between a complete and an incomplete combustion

After this lesson....

... you know how to describe decomposition.

... you know what kind of decomposition exist.

... you know what kind of products we end up with. 

What do we need for a combustion?

1. Fuel and O2
2. Fuel and C
3. Fuel and H20
4. Fuel and CO2

Decomposition Reaction

1 Reactant (always a compound)

2 or more products (Can be elements or other compounds) 

Decomposition

1 reactant

2 or more products

Reactant = a compound

Combustion

2 reactants

1 or more products

Reactant = Fuel + O2

What kind of reaction is:

CuCO​3​​(s)−>CuO(s)+CO​2​​(g)

1. Combustion
2. Decomposition

Most decomposition reactions requiers energy continuously. How do we call this kind of reaction?

1. Exothermic reaction
2. Energy-effect
3. Endothermic reaction

Energy effect of decomposition reactions.

Most decomposition reactions are endothermic.

E.g. Decomposition of limstone:

Limestone(s) --> quicklime(s) + Carbon dioxide(g)

High temperatures. 

Exotherm --> warmte komt vrij

Types of decomposition reactions

Thermal decomposition

Electrolysis

Photolysis

Which substance is formed by decomposition of sugar?

In an oven is quicklime made with heating up limestone . One of the products is Carbon dioxide. What is the formula?

CaCO​3​​

1. CaO(s)−>CaCO​3​​(s)+CO​2​​
2. CaO(s)+CaCO​3​​(s)−>CO​2​​(g)
3. CaCO​3​​(s)−>CaO(s)+CO​2​​(g)
4. CaCO​3​​(s)+CO​2​​(g)−>CaO(s)

What are the 3 types of decomposition?

Sulfer chloride is seperated in sulfer and chloride with the help of the sun.
Which one?

1. Thermal decomposition
2. Electrolysis
3. Photolysis

Water will be separated in hydrogen and oxygen when electric current is passing trough. Which one?

1. Thermal decomposition
2. Electrolysis
3. Photolysis

A hot liquid called aluminium oxide is separated in aluminum and oxygen when an electric source is added. Which one?

1. Thermal decomposition
2. Electrolysis
3. Photolysis

What is in your opinion the most important word of this lesson? (decomposition is not allowed)

Now yourselves!

Make: 18-20 and  22-25 (page 150)