🔎 Physical Properties
Two metal cubes are exactly the same size. Cube A has a mass of 25 g and Cube B has a mass of 60 g. Which cube has the greater density? Explain.
Cube B because it has more mass packed into the same volume.
Material X is colorless, has a density of 0.8 g/mL, does not dissolve in water, and can ignite easily. Which observation is NOT a physical property? Explain.
Its ability to ignite; flammability is a chemical property because burning can form new substances.
: A 20-g piece of aluminum foil is crumpled into a ball. Its shape and volume change. Did its identity change? Classify the change.
No. It remains aluminum, so it is a physical change.
$100: A metal is placed in a liquid. Bubbles form, the temperature changes, and a new solid appears. Which evidence most strongly supports a chemical change?
The formation of new substances, indicated by gas/bubbles and a new solid; the combination of evidence strongly supports a chemical reaction.
Statement A: “Copper conducts electricity.”
Statement B: “Electricity is passing through the copper wire.”
Statement A; conductivity is a physical property.
A substance is shiny, magnetic, has a density of 7.8 g/cmÂł, and conducts electricity. How many physical properties are described?
4 — shininess, magnetism, density, and conductivity.
A metal is described as “highly reactive with acid.” A student says this statement describes a chemical change. Correct the student.
It describes a chemical property because it tells what the metal CAN do, not that the reaction is currently happening.
Ice melts and then refreezes. A student claims two different substances were produced because the state changed twice. Evaluate the claim.
Incorrect. The substance remains water; only its state changes, so both are physical changes.
A student observes bubbles when water boils and says, “Gas formed, so this MUST be a chemical change.” Why is that conclusion incorrect?
Boiling changes liquid water into water vapor; it is still the same substance, so it is a physical change.
Statement A: “Iron can react with oxygen.”
Statement B: “Iron has formed a reddish-brown coating.”
Answer: A = chemical property; B = chemical change.
A student dissolves 10 g of sugar in water. Another student says, “Dissolving proves sugar has a chemical property because it changed.” What is wrong with the student's reasoning?
Dissolving demonstrates a physical property—solubility—and does not require sugar to become a new substance.
A scientist wants to compare two metals without actually causing either one to react. She learns that Metal A can rust while Metal B resists corrosion. What type of information did she collect?
Chemical-property information.
A solid disappears when stirred into water. What additional information would help you determine whether it simply dissolved rather than underwent a chemical change?
Evidence about whether a new substance formed; recovering the original substance by removing the water would also support a physical change.
Two clear liquids are mixed. The mixture becomes cloudy and a solid forms. Why is the solid more important evidence than simply saying “the appearance changed”?
Formation of a new solid can indicate that a new substance formed, which supports a chemical change.
A substance has a melting point of 80°C. A sample is heated to 80°C and begins melting. Explain why the two statements have different classifications.
Melting point is a physical property; actually melting is a physical change.
Materials A and B have the same color and volume. A has a greater mass than B. Which physical property could distinguish them, and what would you predict?
Density; Material A would have the greater density.
Material A and Material B have identical physical properties. Material A reacts with acid while Material B does not. Can the materials still be different substances? Defend your answer.
Yes. Their different chemical properties provide evidence that they may be different substances.
A student cuts a metal wire, bends it, and then heats it until it expands. Three changes occurred. What do they have in common?
They can occur without changing the metal's chemical identity, so they are physical changes.
A nail has a mass of 10.0 g before being left outside. After rusting, its mass is slightly greater. Explain how this observation is consistent with a chemical change.
Iron reacted with oxygen, adding oxygen atoms to form a new substance—iron oxide/rust.
A mystery substance is magnetic, soluble in water, conducts electricity, and reacts strongly with acid. Sort all four observations into physical and chemical properties.
Physical — magnetism, solubility, conductivity. Chemical — reactivity with acid.
A scientist knows an unknown substance's color, texture, and state of matter but still cannot identify it. Name two additional physical properties that could provide stronger evidence and explain why.
Answers vary; density, solubility, conductivity, magnetism, melting point, etc. provide additional measurable/testable evidence.
Explain why “gasoline is flammable” and “gasoline is burning” cannot receive the same classification even though both involve burning.
Flammable describes the ability to burn—a chemical property. Burning describes the chemical change actually occurring.
Crushing and dissolving can both make a substance look dramatically different. Why can appearance alone NOT determine whether a chemical change occurred?
A substance can change form, size, or distribution without becoming a new substance; evidence of a new substance is needed.
A student says, “If a change cannot easily be reversed, it must be chemical.” Give a reason this rule is unreliable.
Reversibility alone does not determine the type of change; classification depends on whether a new substance forms.
A student writes:
Wood burning is a chemical property because wood is flammable.
Wood's flammability/ability to burn is a chemical property; wood actually burning is a chemical change.