Evidence of Chemical Reactions

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. 

Tags

NGSS.MS-PS1-2

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...

• that a gas has formed

• that the color will change

• that there was no chemical change

• that the reaction is happening very fast

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

Tags

NGSS.MS-PS1-2

Hydrogen peroxide breaks down to form water and oxygen gas. Which observation is evidence that a chemical reaction has occurred?

• The mass of the solution remains the same.
•  Phase changes are observed.
•  The color of the solution remains clear.
• The temperature of the solution increases. 

Tags

NGSS.MS-PS1-2

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

• The liquids mix together.

• A yellow solid forms and then settles to the bottom of the beaker.

• The color of the liquids change

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

• Zinc is placed in water and it settles to the bottom

• A piece of paper is cut into pieces

• 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.

Which of the following is evidence of a chemical reactions

• a new substance forms

• a solid dissolved in a liquid

• two liquids mix

• A solid changes to a liquid

A solid forms when two liquids are mixed together. This solid is known as a....

• precipitate

• solution

• mixture

• resultant

You perform a reaction and you feel heat coming off of the beaker. This means that the reaction was

• exothermic

• endothermic

You make slime by mixing glue, contact solution, baking soda, and vinegar. The slime feels cold. Therefore, the reaction was

• exothermic

• endothermic

• a physical change