01 Chemical Foundations and Measurement Online Quiz Questions

Classify each example as a physical property, physical change, chemical property, or chemical change, and justify each classification: wax melting, iron rusting, copper's color, and copper's ability to react with oxygen.

Classify distilled water, salt water, and a mixture of oil and water as pure substances or mixtures. For each, also identify it as an element, compound, homogeneous mixture, or heterogeneous mixture as applicable, and explain your choices.

A uniform sample is divided into smaller portions. Predict what happens to the density, color, mass, and volume of each portion relative to the original sample. Identify each property as intensive or extensive and explain your reasoning.

An object is moved from Earth to a location where the gravitational force on it is different. Explain which of its mass and weight changes, which stays the same, and what each quantity measures.

A graduated cylinder has volume marks every $1.0\ \mathrm{mL}$. The meniscus is at $12.0\ \mathrm{mL}$ plus an estimated $0.4\ \mathrm{mL}$. What volume should be reported? Explain why both $12\ \mathrm{mL}$ and $12.40\ \mathrm{mL}$ would misrepresent the reading.

Determine the number of significant figures in each value and explain the role of its zeros: $0.006070$, $4.500$, and $1.00\times 10^2$.

Calculate $\frac{8.26\times 0.34}{1.20}$ and report the result with the correct number of significant figures. Show the unrounded value and identify which measurement controls the final precision.

Evaluate $15.62+3.1-0.44$. Give the unrounded arithmetic result, determine the least precise decimal place among the inputs, and report the appropriately rounded answer.

Convert a measured temperature of $18.6\ ^{\circ}\mathrm{C}$ to kelvins. Show the conversion, explain why it requires an offset rather than simple multiplication, and report the result at a precision consistent with the measurement.

Convert $0.0048\ \mathrm{km}$ to centimeters using dimensional analysis. Show conversion factors and unit cancellation, then report the result with the appropriate significant figures.

Convert $0.825\ \mathrm{h}$ to seconds by passing through minutes. Show both conversion factors, the units that cancel, and the final value with appropriate significant figures.

A sample has a mass of $28.8\ \mathrm{g}$ and a volume of $12.0\ \mathrm{mL}$. Calculate its density, show that the units are consistent with density being mass divided by volume, and report the result with appropriate significant figures.

A student reads a graduated scale but records only the digits that align exactly with marked graduations. Explain what is missing from the reported measurement and what the final reported digit communicates.

Convert $18.6\ ^\circ\!C$ to kelvins, then use the unrounded result to convert back to degrees Celsius. Show both calculations, report each result with precision appropriate to the measured input, and explain why multiplying by a conversion factor alone would not work.

Convert $0.00840\ \mathrm{km}$ to centimeters using dimensional analysis. Show the conversion factors, the unit cancellations, and how the precision of the starting measurement affects the reported result.

A student claims that density is volume divided by mass. For a sample whose mass is measured in grams and volume in milliliters, use the definition of density and a unit check to explain why the claim is incorrect.

For the measured value $0.006040$, count the significant figures and justify how each zero is treated. Then explain why the precision of $100$ is unclear without additional notation, using two scientific-notation forms to show different intended precisions.

Evaluate $\frac{6.24\times0.035}{2.1}$. Keep extra digits during the calculation, then report the result with the correct number of significant figures and explain how you chose that precision.

Calculate $18.62-3.4$. Show the unrounded result, then report the answer at the precision supported by both measurements and explain the rounding choice.

Four portions are counted, and each has a measured mass of $2.35\ \mathrm{g}$. Find the combined mass and explain why the count of portions does or does not limit the significant figures in your answer.

Convert $2.50\ \mathrm{min}$ to seconds using $60\ \mathrm{s}=1\ \mathrm{min}$. Show the unit cancellation, report the result with appropriate precision, and explain whether the conversion relationship limits significant figures.

A container holds distinguishable pieces of copper and water, and their relative amounts could be changed without changing either material. Classify each component and the combined sample. Explain why the combined sample is not a pure substance and whether it is homogeneous or heterogeneous.

For a sample of iron, classify each of the following and justify your reasoning: its visible color, its tendency to react with oxygen, melting it, and rusting it. Distinguish properties from changes as well as physical from chemical.

A uniform material is divided into several smaller portions. Classify density, color, mass, and volume as intensive or extensive, and explain what happens to each property when the sample is divided.

A process handles material at a rate of $0.0850\ \frac{\mathrm{kg}}{\mathrm{min}}$. Convert this rate to $\mathrm{g/s}$ using $1000\ \mathrm{g} = 1\ \mathrm{kg}$ and $60\ \mathrm{s} = 1\ \mathrm{min}$. Show how the units cancel and report the result with the correct number of significant figures.

Evaluate $(12.11 + 0.3) \times 1.4$ and report the result using the correct precision. Explain how the addition and multiplication rules each affect the final answer, and avoid rounding intermediate values prematurely.

Sample A contains two elements chemically combined in a fixed proportion. Sample B contains two substances physically combined in variable proportions, and each sample of B is uniform throughout. Classify each sample as a pure substance or mixture, further identify its type where applicable, and explain why uniform appearance alone does not make Sample B a pure substance.

A solid is blue, conducts electricity, and can react with oxygen to form different substances. A sample is cut into smaller pieces, and later one piece reacts with oxygen. Classify the color, conductivity, and reactivity as physical or chemical properties; then classify cutting and reaction with oxygen as physical or chemical changes. Justify each classification using whether chemical identity changes.

A uniform sample is divided into four equal portions. Explain what happens to the mass and volume of each portion compared with the original sample, and what happens to its density. Identify which of these properties are extensive and which is intensive, and explain why the density behaves differently from mass and volume.

An object is moved to a location where gravity is weaker, without losing or gaining any material. Explain what happens to its mass and its weight, and why the two quantities respond differently. State appropriate units for reporting its mass.