Chemical and Physical Changes EXAM

Your first name

Your last name

Your class period

• 1st
• 3rd
• 4th
• 5th
• 6th

Students performed a lab investigation on chemical reactions. The students put on goggles and plastic gloves and then followed the steps below. Which observation would indicate that a chemical reaction occurred?

• The vinegar took the shape of the container in step 1
• The steel wool sank into the vinegar in step 3
• The temperature of the vinegar increased during step 4
• The steel wool changed shape during step 6

Which statement best describes evidence that a chemical reaction occurs as a cake bakes?

• The water in the cake batter evaporates
• The cake rises as gas bubbles form in the baking cake
• The cake takes the shape of the container in which it is baked
• The water in the cake batter is used to keep the cake moist as it bakes

Students mixed 2 liquids in a beaker and listed their observations below in the table. Based on these observations which statement contains the best evidence that a chemical reaction occurred?

• There is a change in shape
• There is a change in volume
• The two liquids mix into a solution
• The two liquids form a new substance referred to as a precipitate

Coal contains carbon and other elements. Carbon dioxide forms when coal burns in the presence of oxygen. Which of these is the best evidence that a chemical reaction occurs when coal burns?

• The shape of the coal changes
• Oxygen is present
• A new substance is produced
• Coal is made up of more than 1 element

During an investigation, a student combined the 2 clear colorless solutions shown below in the image. The student observed that the temperature changed from 25 C to 23 C when the solutions were combined and that a white substance rapidly formed and settled to the bottom of the container. What most likely happened to produce these results?

• One of the original compounds came out of solution
• A chemical reaction occurred
• Some of the water froze into ice crystals
• Rapid evaporation of water occurred, leaving a solid

A scientist spilled a few drops of dilute hydrochloric acid (HCl) on a lab table. For safety purposes, the scientist sprinkled some baking soda (NaHCO3) onto 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.

A scientist performed four investigations using eight different liquids. In each investigation, the scientist combined two of the liquids under a fume hood and recorded observations in the table below. In which investigation is it LEAST likely that the liquids reacted chemically?

• Investigation 1
• Investigation 2
• Investigation 3
• Investigation 4