Unit 6 Test: Chemical Reactions

Samara put a quantity of sulfur, a yellow powder, into a test tube. She gently heated the tube and observed that the powder turned black. What happened?

• The sulfur underwent a physical change called melting.

• The sulfur underwent a chemical change called burning.

• The sulfur underwent a chemical change called melting.

• The sulfur underwent a physical change called burning.

The formula for a molecule of serotonin is show below.

C₁₀H₁₂N₂O

How many atoms in all are in the molecule of serotonin?

• 25

• 22

• 10

• 4

Does the following chemical equation follow the Law of Conservation of Mass?

2H₂ + O₂ = 2H₂O

• yes

• no

• not enough information provided

A scientist spilled a few drops of dilute hydrochloric acid (HCl) on a lab table. For safety purposes, the scientist sprinkled some baking soda into the spill. Which observation would provide the best evidence that a chemical reaction occurred?

• The baking soda and hydrochloric acid combined, and bubbles formed.

• The baking soda absorbed the hydrochloric acid.

• Some of the baking soda dissolved in the hydrochloric acid.

• The hydrochloric acid evaporated, leaving only the baking soda.

Which substances have the same number of carbon atoms?

• Substances 1 and 2

• Substances 2, 3 and 4

• Substances 2 and 3 only

• Substances 1 and 3

Which of these example is a physical change?

• 
• 
• 
• 

Is digestion an example of a physical change or a chemical change?

• Physical Change
• Chemical Change

How many elements are in C₆H₁₂O₆?

• 3

• 6

• 12

• 24

How many Nitrogen (N) atoms are in

Fe(NO₃)₂

• 1

• 2

• 3

• 6

The blue numbers in the image below represent ________

• solvents

• coefficients

• subscripts

• elements