Question

You have a glass of liquid and combine it with a mysterious solid and notice that over time the color changes. this questions has two answers
1) give me a scenario that would explain how this coukd be a physical change
2) give me a scenario that would explain how this could be a chemical change

Answer 1

1. This can be due to the dissolving of the solid in liquid and form a solution.

Dissolving is a physical property because dissolving doesn't form new substances and the chemical composition of the solid is not changed.

The color building up over the time can be due to the rate of dissolving of the solid and amount of particles have been dissolved.

Example:

• Dissolving of CuSO₄ solid in water.
• This develops a blue color.

2. This can be due to the chemical reaction between the solid and liquid.

Chemical reaction is a chemical property because from reacting substances new substances can be formed which the chemical formula is different from initial substances.

The color building up over the time can be due to the rate of the reaction and the amount of reactants.

Example:

• The reaction between calcium metal with water.
• The color of Ca(OH)₂ is white color.
• Reaction is

       Ca(s) + 2H₂O(l) → Ca(OH)₂(aq) + H₂(g)