Evidence of Chemical Change

The Best Friend's Club uses "invisible ink" to write notes to each other. The invisible ink is actually lemon juice that is clear when it dries on paper, but turns brown when a club member holds a burning candle under the paper. Once it is heated, it is never invisible again.

What type of change is occurring when the paper is heated?

• Chemical Change

• Physical Change

• Elemental Change

• Temperature Change

Tags

NGSS.MS-PS1-2

A student mixes two clear liquids together. After a few minutes, a white powdery solid can be seen settling on the bottom of the test tube. Which of the following is a conclusion that the student can draw based on these observations? The two clear liquids-

• were pure substances before they were mixed

• are toxic and should be handled with extreme caution

• have gone through a chemical change in which a new substance called a precipitate was produced

• have been stored too long and are no longer good

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

A student added white crystals to a clear liquid. The crystals dissolved in the liquid. After a few seconds, the liquid became quite warm and then turned bright red in color. Indications that a chemical change was taking place could be observed when –

• the white crystals were added to the clear liquid.

• the crystals dissolved in the liquid leaving only the liquid visible

• There are no indications of chemical change

• the temperature of the liquid increased and an unexpected color change occurred.

Tags

NGSS.MS-PS1-2

A student observes some sugar as it is heated and burns. The student concludes that a chemical reaction has occurred. Which of the following observations about the burning sugar provides evidence of a chemical reaction?

• Heat is added to the sugar crystals.

• The sugar melts and becomes a liquid.

• Gas is produced as the sugar turns black.

• No evidence of chemical reaction is present.

Tags

NGSS.MS-PS1-2

During an experiment, a student observes a color change when two substances are mixed. What type of evidence does this provide?

• Evidence of a physical change

• Evidence of a chemical change

• Evidence of a state change

• Evidence of a mixture

Tags

TEKS.SCI.6.6E

DOK Level 3: Strategic Thinking

What evidence(s) of a chemical reaction do you see in the pictures? (Select all that are correct)

• Gas

• Precipitate

• Color Change

• Giving off light

Tags

NGSS.MS-PS1-2

Which of the following observations would best indicate a chemical change has occurred?

• The substance changes shape

• The substance changes color

• The substance is cut into pieces

• The substance is mixed with water

Tags

TEKS.SCI.6.6E

DOK Level 2: Skill/Concept

Which observation(s) might be used as evidence that a chemical reaction occurred?

• Color change

• Odor change

• Properties change

• All of the above

Tags

NGSS.MS-PS1-2

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.

• The solutions reacted chemically.

• Some of the water froze into ice crystals.

• Rapid evaporation of water occurred, leaving a solid.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

The only sure evidence of a chemical reaction is.... (a)  

• the formation of a gas.

• a color change.

• the production of a new substance.

Tags

NGSS.MS-PS1-2