What Happened?
Ice melting is what type of change?
Physical change
A student mixes two substances in a test tube. After mixing, the test tube begins to glow.
What evidence of a chemical change did the student observe?
A. Gas
B. Light
C. Precipitate
D. Odor
B. Light
What happens to matter during a physical change?
Its form or appearance changes, but no new substance forms.
Baking soda and vinegar react and produce bubbles. What evidence supports a chemical change?
Gas production
A student says, “A chemical change only happens when a substance changes color.”
Is the student correct? Explain your answer and give an example of another type of evidence.
Answer: No. Other evidence can include gas production, light, precipitate formation, unexpected temperature change, or a new odor.
A student mixes two substances and notices that the container becomes unexpectedly cold.
What evidence of a chemical change was observed?
A. Unexpected temperature change
B. Color change
C. Gas
D. Light
Answer: A. Unexpected temperature change
A student changes a piece of paper from a rectangle into a triangle by cutting it.
Is this evidence of a chemical change?
A. Yes
B. No
Answer: B. No
Crushing a can is what type of change?
Physical change
Why can't burning paper easily be changed back into paper?
A new substance called ash forms during the chemical change.
A student puts an ice cube in a cup. The ice melts, and the student says, “A new substance formed because the ice looks different.”
What mistake did the student make?
Answer: The student confused a change in appearance/state with the formation of a new substance. The ice is still water, so it is a physical change.
Water freezing into ice is what type of change?
Answer: Physical
1. A student breaks a glass cup into several pieces. The pieces are smaller, but they are still glass. What type of change occurred? Explain your reasoning.
Answer: Physical change because the size and shape changed, but no new substance formed.
A student notices that a substance suddenly begins giving off a strong smell after being mixed with another substance. What evidence did the student observe?
Answer: A new or unexpected odor, which can be evidence of a chemical change.
2. A student leaves a wet towel outside. After several hours, the towel is dry. What happened to the water? Is this a physical or chemical change?
The water evaporated. It was a physical change because the water remained the same substance.
Two clear liquids are mixed. The mixture becomes cloudy, a solid forms, and the temperature unexpectedly decreases.
What type of change most likely occurred? Identify two pieces of evidence that support your answer.
Answer: A chemical change most likely occurred. Evidence includes the formation of a precipitate and the unexpected temperature change.
Change A: Water is heated until it becomes steam.
Change B: A clear liquid is mixed with another clear liquid. The mixture unexpectedly turns yellow, becomes warm, and produces a new odor.
Which statement is correct?
A. Both are chemical changes because both involve a temperature change.
B. Change A is physical, while Change B is chemical.
C. Change A is chemical, while Change B is physical.
D. Both are physical changes because no solid formed.
Answer: B. Change A is physical, while Change B is chemical.
During an investigation, two substances are mixed. A solid suddenly forms and sinks to the bottom of the container.
Which observation provides evidence that a chemical change may have occurred?
A. The substances were mixed
B. A solid precipitate formed
C. The container was opened
D. The liquid took the shape of the container
B. A solid precipitate formed
3. A student mixes two solutions. A white solid suddenly appears at the bottom of the container. The student did not add any solid to the mixture. What happened?
You must use the sciencetific word.
Precipitate
student is investigating whether mixing two substances causes a chemical change.
Which set of observations gives the best evidence that a chemical change occurred?
A. The substances were poured into a larger container.
B. The mixture was stirred and changed shape.
C. The mixture produced gas, an unexpected odor, and an unexpected temperature change.
D. The student measured the substances before mixing.
Answer: C.
A student observes a candle burning. At the same time, some of the wax melts.
Explain why two different types of changes are occurring during the same event.
Answer: The melting wax is a physical change because the wax changes state but remains the same substance. The burning wax is a chemical change because new substances are produced during combustion.
A student mixes two substances. The mixture becomes unexpectedly warmer, produces a new odor, and a solid forms at the bottom of the container. Is this a physical or chemical change? Use at least two pieces of evidence to support your answer.
Answer: Chemical change. The unexpected temperature change, new odor, and formation of a precipitate are evidence that new substances may have formed.
A student mixes two substances. The mixture begins to glow, produces bubbles, and becomes warmer.
Which conclusion is best supported by the evidence?
A. A physical change definitely occurred.
B. The substances changed states of matter.
C. Evidence suggests that a chemical change occurred.
D. Nothing changed because the substances are still in the container.
C. Evidence suggests that a chemical change occurred.
During an investigation, a student records the following:
"The two solutions were clear before mixing. After mixing, the solution unexpectedly turned yellow. A solid also formed at the bottom of the container."
Which TWO pieces of evidence suggest that a chemical change may have occurred?
A. The solutions were liquids.
B. An unexpected color change occurred.
C. The liquids were clear before mixing.
D. A precipitate formed.
Answer: B and D
A student says, “Any color change means a chemical change.” Is the student always correct? Explain.
No. A color change can be evidence of a chemical change, but it does not automatically prove one occurred. Scientists should consider multiple pieces of evidence
A mystery substance undergoes a change. Scientists observe:
What is the most likely type of change? Defend your answer using evidence.
Answer: Physical change. The substance changed state from solid to liquid, and there is no evidence listed that a new substance formed.