EXPERIMENTAL SETUP 

In this experiment, the rectangular copper strip is attached to the positive terminal of a battery and the nail is attached to the negative terminal of the battery.  Then both are submerged in a solution of water and dissolved copper 

BACKGROUND KNOWLEDGE 

• The copper strip is made of copper , which is an element and only made of copper  atoms

• Copper atoms are neutral in this state (protons and electrons are equal)

• Elemental (neutral) copper will not dissolve in water 

OBSERVATIONS 

When the power is turned on:

• Copper metal starts to accumulate on the negatively charged nail

• The liquid under the copper strip looks "wavy" like something is coming off of it

• The mass of the copper strip decreases (it was weighed before and after)

DRIVING QUESTIONS: 

• What is the power supply doing that is making the copper strip dissolve?  

• Why is copper unable to dissolve when it is not hooked up to the power supply? 

• Why is undissolved copper forming on the nail?

• Is your knowledge of water particles helpful in understanding this? 

• How do atoms get charged?  Which parts of the atom are involved, which are not? How do you know?  

CONCLUSIONS:

Claim 1 - When copper  is positively charged, it will dissolve in the water.  When it is neutral is will not. 

Evidence:  The copper strip did not dissolve in the water until it was attached to the battery and the battery was turned on.  The copper strip dissolved when it was attached to the battery and the battery was turned on. 

Reasoning:  When the copper strip is attached to the positive part of the battery, it means that the copper strip is being made positive and therefore the atoms of copper are being made positive.  

When this happens the copper strip loses mass and it looks like something is coming off of the strip and going into the water.   According to the law of conservation of mass, the copper atoms cannot be created or destroyed.  Because the mass of the strip decreases, they must no longer be with the strip but they have to be somewhere.  Since the copper was submerged in water and it appears that something was leaving the strip and going into the water, it seems some copper  atoms must now be in the water but they cannot be seen.  This means that they have dissolved.  Since this did not happen to the strip before the battery was hooked up, it means that neutral copper does not dissolve in water. 

In addition, copper  metal is forming on the negatively charged nail.  This suggests that the copper attaching to the nail is positive.  Since the copper strip and the nail are not touching each other, it means that the copper forming on the nail must have come from the water which supports the earlier conclusion that the copper atoms were coming off of the strip. 

Claim 2 - Copper  atoms are losing electrons at the positive terminal and gaining electrons at the negative terminal. 

Evidence: Copper is dissolving at the positive terminal and copper is undissolving (precipitating chemically) at the negative terminal. 

Reasoning: Copper dissolves when it is positive and does not dissolve when it is neutral.  Atoms are neutral when they have the same amount of protons and electrons.  If atoms lose electrons, they become positive, if they gain electrons they become negative. 

Since the copper that was coming off of the strip was dissolving, it was positive and therefore lost electrons.  The copper that is now dissolved in the liquid is positive and it attracted to the negative terminal, where it can no longer dissolve.  This means the copper must be neutral.  If is was positive but it is now neutral, it must have gained electrons.