When two substances react chemically, the product of the chemical reaction —

A. will have very similar properties to the reactants
Incorrect. The product of a chemical reaction will have different properties than the reactants.

B. will have very different properties to the reactants
Correct!

C. cannot be predicted
Incorrect. The products of a chemical reaction can be predicted.

D. vary from reaction to reaction
Incorrect. The products of a certain chemical reaction will be the same each time the reaction is performed.

Which of the following is an example of a chemical change?

A. baking a cake
Correct!

B. cutting a cake
Incorrect. Cutting is a physical change.

C. cracking eggs
Incorrect. Cracking the eggs is a physical change.

D. mixing sugar and salt
Incorrect. Mixing sugar and salt is a physical change.

A sealed flask of a clear, colorless liquid is left sitting on an interior sunny windowsill. After about an hour, there are droplets of a clear liquid on the outside of the flask. The solution inside the glass has turned yellow. After two hours, the solution is dark brown with clear, colorless droplets of liquid on the glass. After sitting on the windowsill for a week, the walls of the flask have a silvery lining, and both the solution and the droplets are clear and colorless.

Which of the following is an indication that a chemical reaction has occurred?

  1. The formation of droplets on the outside of the flask
  2. The solution color changing from clear to yellow
  3. The solution color changing from brown to clear
  4. Formation of a silvery metallic foil on the walls of the flask

A. I and II only
Incorrect. A color change is an indication that a chemical change has taken place, but the formation of droplets on the outside of the flask is not an indication of a chemical change.

B. I and III only
Incorrect. A color change is an indication that a chemical change has taken place, but the formation of droplets on the outside of the flask is not an indication of a chemical change.

C. II and III only
Incorrect. The color changes are indication that a chemical change has taken place, but what other evidence is there?

D. II, III, and IV
Correct!

A sealed flask of a clear, colorless liquid is left sitting on an interior sunny windowsill. After about an hour, there are droplets of a clear liquid on the outside of the flask. The solution inside the glass has turned yellow. After two hours, the solution is dark brown with clear, colorless droplets of liquid on the glass. After sitting on the windowsill for a week, the walls of the flask have a silvery lining, and both the solution and the droplets are clear and colorless.

The formation of the silvery lining is an example of which of the following indicators of a chemical change?

A. Formation of a gas
Incorrect. The silvery lining is not a gas.

B. Color change
Incorrect. This is not an example of a color change because the silvery lining is a new substance.

C. Formation of a precipitate
Correct!

D. Temperature change
Incorrect. The formation silvery lining does not indicate that a temperature change has taken place.