Chemical Change_6.2

Which of the following examples shows that a chemical reaction has occurred? 

• A rock breaks into smaller pieces when it is struck with a hammer.
• Rust forms on a hammer that has been left outside to long. 
• A cup of water turns pink when a few drops of red food coloring are added. 
• A solid is formed when heat is removed from a sample of water. 

A student places a piece of a potato into a container of hydrogen peroxide. One observation the student makes is that bubbles form around the potato. The presence of bubbles might indicate the formation of a new substance because bubbles - 

• could show that a gas is forming
• always rise to the top of a liquid. 
• are almost always perfectly spherical.
• usually burst after a few minutes.

Four students performed four different investigations by combining different substances. Their results are shown in the table provided. In which experiment are new substances being formed?

• Experiment 1
• Experiment 2
• Experiment 3
• Experiment 4

A clear liquid from a flask is poured into another clear liquid in a beaker. Which of the following results of this procedure would indicate a new substance was formed?

• The level of the substance in the beaker is higher after the other liquid is added.
• A yellow solid forms and then settles to the bottom of the beaker.
• Small white crystals are left behind in the flask that held the first liquid.

Which of the following is an example that includes evidence of a chemical reaction?

• A sample of zinc is placed in water and it settles to the bottom
• A solid block of ice is heated and it completely melts into a liquid. 
• Sugar that is burned gives off an odor and turns brown and then black.
• A tomato is placed into a blender and chopped up into smaller pieces.

Evidence of a chemical reactions is anything that shows - 

• a new substance has formed
• a solid dissolved in a liquid
• interaction between 2 gases
• a change in the state of matter

Which of the following is NOT evidence that that a chemical reaction has occurred?

• produces light/heat
• production of a gas
• formation of a precipitate
• melting

Which of the following equations demonstrates an actual chemical reaction that forms a new substance?

• A
• B
• C
• D

The reactants are on the left side of the chemical equation.

• True
• False

Which of these is NOT a sign that a chemical change has occurred?

• A loss of transparency

• An unexpected color change

• A temperature change

• The formation of a precipitate