Lesson 3.2: Corrosion

Corrosion costs billions of dollars every year.  Corrosive substances are responsible for injuring and killing many people every year. 

What is corrosion?  Is it something that can be prevented? 

Read Corrosion and What Affects Corrosion on page 71 in your textbook. Then, complete the following questions.

Question 1. What is corrosion?

Question 2: What kinds of substances are corrosive?

Question 3: What is the symbol used to indicate that a substance is corrosive?

Question 4. What is acid rain?

Question 5: How can you tell if rain is ordinary rain or acid rain?

Question 6: What effect does acid rain have on living things? 

Question 7: What effect does acid rain have on non-living things? 

Question 8: What causes acid rain? 

Question 9: Salt and water are a corrosive mixture.  What is the effect of salt and water on a ship? 

Question 10: What gas is mainly responsible for corrosion?

Question 11: What is the effect of temperature on corrosion? 

 

Check your answers with those that follow.

 

 

 

 

 

 

 

 

 

 

 

 

Answers to Questions:

Question 1. What is corrosion?

Corrosion is the wearing away of materials by chemical action.  Rusting is one form of corrosion that you are likely familiar with.

Question 2. What kinds of substances are corrosive?

Many substances are corrosive.  The reading on page 71 tells you that substances at the ends of the pH scale are highly corrosive.  This means strong acids and bases are highly corrosive.  Oxygen is a gas that reacts with many materials and causes them to corrode.  Salt and water speed up corrosion.

Question 3. What is the symbol that indicates a substance is corrosive?

The symbol that indicates a substance is corrosive is shown here.

Question 4. What is acid rain?

Acid rain is any precipitation that has a pH less than 5.6.  The precipitation can be in many forms such as rain, snow, sleet, hail, or fog.

Question 5. How can you tell if rain is ordinary rain or acid rain?

Determining rain to be ordinary rain or acid rain is difficult.  You cannot feel or taste the difference.  You must measure the pH of the rain to tell the difference.

Question 6. What effect does acid rain have on living things?

Acid rain corrodes living things. You can see the marks on the leaves in Figure 4.10 on page 70. 

In addition, acid rain can have some effects not discussed in the reading.  Acid rain can leach harmful metals from the soil. Plants then absorb these metals, and they are damaged or may even die.  These harmful metals can be washed into lakes and rivers where they can cause harm to organisms that live in the water.  The acid rain can lower the pH of lakes to the point that the water is so acidic that nothing can live in there.

Question 7. What effect does acid rain have on non-living things?  

Acid rain corroded non-living substances such as stone and metal.  Buildings, bridges, vehicles, and other things people make are being corroded by acid rain.  Any stone sculptures that are exposed to the weather are being damaged by acid rain.

Question 8. What causes acid rain? 

Acid rain is caused by pollutants that react with water in the air.  These pollutants are produced whenever we burn fossil fuels in our cars, power plants, factories, and home furnaces.  Some of the pollutants responsible for acid rain are sulphur and nitrogen oxides.

Question 9. Salt and water is a corrosive mixture.  What is the effect of salt and water on a ship? 

Salt and water speed up corrosion.  That is why cars rust faster when salt is put on the roads to get rid of ice and snow.  An iron ship in salt water will corrode quickly (rust) in salt water unless it is protected from corrosion.

Question 10. What is the gas mainly responsible for corrosion?  

The gas mainly responsible for corrosion is oxygen.  Other gases mentioned in the answer to question 8 are sulphur and nitrogen oxides produced when fossil fuels are burned.

Question 11. What is the effect of temperature on corrosion?   

The higher the temperature, the faster the corrosion.  This is because corrosion is a chemical reaction and chemical reactions are speeded up by higher temperatures.  Another factor not discussed in the text involves evaporation.  In higher temperatures, water evaporates more rapidly.  If you remove the water and the material is dry, then corrosion will almost stop because water is an important substance for corrosion to occur.  The best way to store your car is to keep it warm, clean, and dry.  The worst way to store your car is to keep it warm, salt covered, and wet.

 


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