Purpose:
Sulfur in hot water reacts with aluminum to produce gas, hydrogen sulfide and aluminum hydroxide, which pits and makes a white coating on the aluminum foil. Baking soda makes the solution capable of conducting electric current, which allows the reaction between aluminum and silver to occur. It also helps remove the coating on the foil, exposing fresh aluminum.
Materials:
- tarnished spoon
- baking soda
- three glass jars
- aluminium foil
- safety glasses
- hot water
Procedure:
As always, wear safety glasses.
- Fill one beaker with water. This is your rinse beaker.
- Fill the other two beakers with hot water. Add a teaspoon of baking soda to each and stir.
- Wrap the bowl of a tarnished spoon tightly with aluminum foil. Put the spoon, handle up, in one of the baking-soda beakers. Wait one minute.
- Remove the spoon. Rinse it. Remove the aluminum foil gently. What happened to the tarnish?
- Crumple up a small piece of aluminum foil and put it in the second beaker. Now place the same spoon, handle down, in the beaker. Don't let it touch the aluminum foil. Wait a minute, then take it out and rinse it. What happens to the tarnish this time?
- Compare the aluminum foil you used with new, unused foil. You may need a magnifying glass.
Follow-up Discussions:
In air, silver (Ag) reacts with hydrogen sulfide (H2S) to make black silver sulfide (Ag2S), or tarnish. Aluminum (Al) is more reactive than silver; therefore, when the tarnished silver spoon touches the foil, sulfur is released from the silver sulfide and shiny silver is left behind. If the spoon doesn't touch the aluminum, nothing happens. Baking soda allows the reaction to occur by making the solution conduct electric current, and by cleaning the foil to expose fresh aluminum.
Materials:
- tarnished spoon
- baking soda
- three glass jars
- aluminium foil
- safety glasses
- hot water
Procedure:
As always, wear safety glasses.
- Fill one beaker with water. This is your rinse beaker.
- Fill the other two beakers with hot water. Add a teaspoon of baking soda to each and stir.
- Wrap the bowl of a tarnished spoon tightly with aluminum foil. Put the spoon, handle up, in one of the baking-soda beakers. Wait one minute.
- Remove the spoon. Rinse it. Remove the aluminum foil gently. What happened to the tarnish?
- Crumple up a small piece of aluminum foil and put it in the second beaker. Now place the same spoon, handle down, in the beaker. Don't let it touch the aluminum foil. Wait a minute, then take it out and rinse it. What happens to the tarnish this time?
- Compare the aluminum foil you used with new, unused foil. You may need a magnifying glass.
Follow-up Discussions:
In air, silver (Ag) reacts with hydrogen sulfide (H2S) to make black silver sulfide (Ag2S), or tarnish. Aluminum (Al) is more reactive than silver; therefore, when the tarnished silver spoon touches the foil, sulfur is released from the silver sulfide and shiny silver is left behind. If the spoon doesn't touch the aluminum, nothing happens. Baking soda allows the reaction to occur by making the solution conduct electric current, and by cleaning the foil to expose fresh aluminum.
- tarnished spoon
- baking soda
- three glass jars
- aluminium foil
- safety glasses
- hot water
Procedure:
As always, wear safety glasses.
- Fill one beaker with water. This is your rinse beaker.
- Fill the other two beakers with hot water. Add a teaspoon of baking soda to each and stir.
- Wrap the bowl of a tarnished spoon tightly with aluminum foil. Put the spoon, handle up, in one of the baking-soda beakers. Wait one minute.
- Remove the spoon. Rinse it. Remove the aluminum foil gently. What happened to the tarnish?
- Crumple up a small piece of aluminum foil and put it in the second beaker. Now place the same spoon, handle down, in the beaker. Don't let it touch the aluminum foil. Wait a minute, then take it out and rinse it. What happens to the tarnish this time?
- Compare the aluminum foil you used with new, unused foil. You may need a magnifying glass.
Follow-up Discussions:
In air, silver (Ag) reacts with hydrogen sulfide (H2S) to make black silver sulfide (Ag2S), or tarnish. Aluminum (Al) is more reactive than silver; therefore, when the tarnished silver spoon touches the foil, sulfur is released from the silver sulfide and shiny silver is left behind. If the spoon doesn't touch the aluminum, nothing happens. Baking soda allows the reaction to occur by making the solution conduct electric current, and by cleaning the foil to expose fresh aluminum.
- Fill one beaker with water. This is your rinse beaker.
- Fill the other two beakers with hot water. Add a teaspoon of baking soda to each and stir.
- Wrap the bowl of a tarnished spoon tightly with aluminum foil. Put the spoon, handle up, in one of the baking-soda beakers. Wait one minute.
- Remove the spoon. Rinse it. Remove the aluminum foil gently. What happened to the tarnish?
- Crumple up a small piece of aluminum foil and put it in the second beaker. Now place the same spoon, handle down, in the beaker. Don't let it touch the aluminum foil. Wait a minute, then take it out and rinse it. What happens to the tarnish this time?
- Compare the aluminum foil you used with new, unused foil. You may need a magnifying glass.
Follow-up Discussions:
In air, silver (Ag) reacts with hydrogen sulfide (H2S) to make black silver sulfide (Ag2S), or tarnish. Aluminum (Al) is more reactive than silver; therefore, when the tarnished silver spoon touches the foil, sulfur is released from the silver sulfide and shiny silver is left behind. If the spoon doesn't touch the aluminum, nothing happens. Baking soda allows the reaction to occur by making the solution conduct electric current, and by cleaning the foil to expose fresh aluminum.
Reprinted courtesy of the CMA Chemical Science Center, at the Capital Children's Museum, Washington, DC.
