Rusting

Question 1

What is steel a mixture of?

Answer 1

the metal iron and the non-metal carbon

Question 2

What is an alloy?

Answer 2

a mixture containing a metal and at least one other element

Question 3

What is rust?

Answer 3

a brown, flaky solid

Question 4

What happens when iron and steel change to rust?

Answer 4

they become very weak

Question 5

Why do iron and steel become weak when they change to rust?

Answer 5

because rust breaks easily and this robs the iron and steel of the property we need

Question 6

What is the method of the experiment to find out what creates rust?

Answer 6

1. Take 6 test tubes.
2. In the first tube stand an iron nail in the air, with no added chemicals (control).
3. In the second test tube place a few pieces of anhydrous calcium chloride in the tube followed by an iron nail. Stopper the tube. Label this TUBE 1.
4. In the third tube place an iron nail and some tap water.
5. In the fourth tube place an iron nail then cover the nail with boiled water. Add some vegetable oil, which will float on top of the water, then stopper
   the tube.
6. In the fifth test tube place a nail and some salt solution.
7. In the final tube place an iron nail that has been partially wrapped with some zinc foil then add some tap water taking care not to cover the nail.
8. Leave the tubes for one week in order to see what happens.

Question 7

Does the nail rust with air?

Answer 7

no

Question 8

Does the nail rust with dry air?

Answer 8

no

Question 9

Does the nail rust with water and air

Answer 9

yes

Question 10

Does the nail rust with boiled water only?

Answer 10

no

Question 11

Does the nail rust with air and salt solution?

Answer 11

yes

Question 12

Does the nail rust with zinc metal, water and air?

Answer 12

no

Question 13

Does the nail rust with zinc metal, water and air?

Answer 13

no

Question 14

Why was the water boiled in test tube D?

Answer 14

To remove dissolved gases from the water (i.e. oxygen)

Question 15

Why was oil added to the boiled water?

Answer 15

To prevent gases redissolving in the water as it cools down.

Question 16

Why should the test tube be stoppered with a bung?

Answer 16

To keep air out of the tube.

Question 17

What does the drying agent (anhydrous calcium chloride) do?

Answer 17

Absorbs all the water vapour keeping the nail perfectly dry.

Question 18

What does the zinc in test tube F do?

Answer 18

Zinc is more reactive than iron and corrodes first. This prevents the iron
from rusting. This is known as sacrificial protection.
Any more reactive metal will protect the iron in this way (e.g. magnesium)

Question 19

What does the experiment tell us about rusting and how it can be prevented?

Answer 19

Iron has to be in contact with both air (oxygen) and water to be able to rust. Dissolved salt speeds up the process of rusting. If the iron is in contact with a more reactive metal, it does not rust. The more reactive metal corrodes first.

Question 20

What is the difference between oxidation and corrosion?

Answer 20

there is no difference; they are the same

Question 21

What is a physical barrier?

Answer 21

something put on the surface of the iron to stop it
coming into contact with air and water

Question 22

What is sacrificial protection?

Answer 22

having the iron in contact with a more reactive metal, which corrodes first.

Question 23

What are the two substances needed for rusting of iron and steel to occur?

Answer 23

water and oxygen

Question 24

What is the word equation for rusting?

Answer 24

iron + oxygen + water → hydrated iron (lll) oxide (rust)

Question 25

What is the effect of salting roads on cars?

Answer 25

it speeds up the rusting of cars

Question 26

What are ways of protecting cars against rusting?

Answer 26

-painting
-oiling
-electroplating
-galvinising

Question 27

What kind of change is rust?

Answer 27

a chemical change

Question 28

What are some examples of physical barriers?

Answer 28

-painting
-oiling
-greasing
-covering with plastic
-electroplating

Question 29

How does sacrificial protection work?

Answer 29

A more reactive metal makes contact with the iron (either directly or via a connecting wire). This metal corrodes first and prevents the iron from rusting.

Question 30

What is galvanising?

Answer 30

a method combines both a physical barrier and sacrificial protection. For example, Iron is dipped into molten zinc, which then solidifies on the surface forming a physical barrier to air and water. If the surface layer of zinc is scratched exposing the iron, rusting will still not occur as zinc is more reactive than iron and will corrode first.