- A clean steel wool
- Tap water
- Salt water
- Three paper cups
- At first cut out the steel wool into three pieces.
- Then place each piece in a paper cup.
- Fill one cup with enough tap water to submerge the piece of steel wool.
- Then fill the 2nd cup with salt water to submerge another piece of steel wool.
- Again fill the last cup with enough vinegar to submerge the piece of steel wool.
- Examine the three submerged pieces of steel wool after fifteen minutes.
- Record any kind of changes.
- Examine the pieces of steel woo after 2 hours.
- Record if there is any change.
- Examine the pieces of steel wool once a day for about 3 or 4 days.
- Record any kind of change you observe.
- A brown layer of rust is developed on all the pieces of steel wool over time.
- The piece of steel wool which was in the vinegar starts to show signs of rusting almost immediately.
- The steel wool piece that was in the salted water shows signs of rusting within a couple of hours.
- The steel wool piece that was in the tap water starts to rust in about 3 days.
Steel wool is made of iron. When iron reacts with the oxygen in the air a substance called iron oxide is created. It’s commonly known a rust.
The reaction is :
|Rust form through Chemical Reaction|
For the reaction to happen, some of the iron metal becomes iron ions in a process called ionization. Ions are electrically charged atoms which have changed chemically to either loose or gain electron. Iron metal can slowly ionize in the water. That’s why wet iron rusts. The iron ions can react with the oxygen dissolved in the water to create iron oxide. However, in salt or acidic solutions, the ionization process is a lot quicker.
In this experiment naturally the salted water is a salted solution. The presence of salt in the water boosts up the ionization process of the iron enough to make the rust visible within a couple of hours or a bit more. However, the vinegar is way better at ionizing iron. Vinegar is actually acetic acid. It can make iron oxide appear on iron within a few minutes.
The chemical reaction which causes the rust to form on iron is actually a type of corrosion. It’s the equivalent of the chemical reaction that causes green layer to appear on American pennies or copper. (To know more about this, you can read the experiment Make your coins green!) The only difference is that while pennies corrode and copper oxide is formed, the layer of copper oxide actually protects the metal underneath. But on the other hand, iron oxide destroys iron metal over time and make it fragile and useless.
MORE EXPERIMENTS FOR YOU:
- Use other kinds of acids to see and compare the effect.
- Use sugar water to see the effect!
- Can the rust be dissolved using other kinds of acids?