Rusting Flashcards
What is steel a mixture of?
the metal iron and the non-metal carbon
What is an alloy?
a mixture containing a metal and at least one other element
What is rust?
a brown, flaky solid
What happens when iron and steel change to rust?
they become very weak
Why do iron and steel become weak when they change to rust?
because rust breaks easily and this robs the iron and steel of the property we need
What is the method of the experiment to find out what creates rust?
- Take 6 test tubes.
- In the first tube stand an iron nail in the air, with no added chemicals (control).
- 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.
- In the third tube place an iron nail and some tap water.
- 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. - In the fifth test tube place a nail and some salt solution.
- 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.
- Leave the tubes for one week in order to see what happens.
Does the nail rust with air?
no
Does the nail rust with dry air?
no
Does the nail rust with water and air
yes
Does the nail rust with boiled water only?
no
Does the nail rust with air and salt solution?
yes
Does the nail rust with zinc metal, water and air?
no
Does the nail rust with zinc metal, water and air?
no
Why was the water boiled in test tube D?
To remove dissolved gases from the water (i.e. oxygen)
Why was oil added to the boiled water?
To prevent gases redissolving in the water as it cools down.
Why should the test tube be stoppered with a bung?
To keep air out of the tube.
What does the drying agent (anhydrous calcium chloride) do?
Absorbs all the water vapour keeping the nail perfectly dry.
What does the zinc in test tube F do?
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)
What does the experiment tell us about rusting and how it can be prevented?
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.
What is the difference between oxidation and corrosion?
there is no difference; they are the same
What is a physical barrier?
something put on the surface of the iron to stop it
coming into contact with air and water
What is sacrificial protection?
having the iron in contact with a more reactive metal, which corrodes first.
What are the two substances needed for rusting of iron and steel to occur?
water and oxygen
What is the word equation for rusting?
iron + oxygen + water → hydrated iron (lll) oxide (rust)
What is the effect of salting roads on cars?
it speeds up the rusting of cars
What are ways of protecting cars against rusting?
-painting
-oiling
-electroplating
-galvinising
What kind of change is rust?
a chemical change
What are some examples of physical barriers?
-painting
-oiling
-greasing
-covering with plastic
-electroplating
How does sacrificial protection work?
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.
What is galvanising?
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.
