Investigating Matter — Extension · Physical Science: Chemistry, Grade 11
Build the measurement, classification, and evidence skills used throughout chemistry.
Density and Measurement Evidence
Investigate
Does density stay approximately constant across sample sizes?
Use two dedicated sessions: first define the model, boundary, variables and comparison, then collect suitable records or analyze the complete supplied-data route; second complete calculations/graphs, compare alternatives, revise and prepare the report. Extend collection time where needed. Supplied-data work does not certify supervised laboratory minutes or mandated investigations.
Materials
- Balance and graduated container, if available
- Room-temperature water, three small containers
- Paper/calculator; provided data can be used
Before you begin
Use only the listed household materials or analyze the supplied data. An adult should review setup. No flames, strong acids/alkalis, unknown chemicals, household mains, radiation sources, or high-speed projectiles are needed. Keep food-study materials separate from eating and wash hands afterward.
Plan a fair test
Vary water volume; measure mass. Keep temperature, tare method, and equipment comparable.
Method
- Write a prediction and the physical/chemical mechanism behind it.
- Draw the setup or system boundary; label variables and units.
- Tare each dry container and measure water volume without spills.
- Record net water mass for each volume; repeat independently three times per volume.
- Plot net mass against volume; calculate density and compare scatter.
- Record repeated observations where possible; keep original readings and note resolution or uncertainty.
- Write a claim supported by specific numbers, explain the mechanism, and identify one limitation and a next test.
Example data — for analysis when materials are unavailable
Illustrative teaching data, not measurements from a real district laboratory. Analyze these when materials are unavailable and identify them as provided data. Do not claim to have performed a measurement you did not make.
| Volume(mL) | Mass trial 1(g) | Trial 2(g) | Trial 3(g) |
|---|---|---|---|
| 10 | 9.9 | 10.1 | 10 |
| 20 | 20 | 19.9 | 20.1 |
| 30 | 30.1 | 29.9 | 30 |
Analyze and explain
- Calculate mean mass and density for each size.
- Does the intercept/slope suggest any offset?
- Which evidence checks precision and which could check accuracy?
- Link the pattern to a labeled particle, structure, energy or amount model from the chapter.
- Distinguish supplied illustrative records from measurements actually collected.
- Identify uncertainty and propose a comparison that would test an alternative explanation.
What a strong explanation includes
- A stated prediction, conditions, and controlled variables or explicit model boundary.
- A labeled table/graph with units, calculations, and attention to repeated values or uncertainty.
- A claim citing numerical evidence and a scientifically accurate mechanism.
- A limitation, alternative explanation, and useful follow-up test.
- Preserve initial reasoning and an evidence-supported revision.
- Check units, species identity, system boundary and physical assumptions.
Parent / teacher guide: discuss after the investigation
Mean masses are 10,20,30 g; all give 1.00 g/mL. Repeats span.2 g, supporting approximate consistency in this illustrative range. A known calibration mass or independent volume standard would address accuracy; the repeats alone do not exclude common bias. Preserve the original observations, intermediate working and a labeled mechanism. Report the relevant boundary and model assumptions, discuss an alternative explanation, and identify the next useful measurement; do not replace unexpected data with the illustrative record.
Compare this model with the learner’s actual evidence. Different measurements can support a different conclusion; check the reasoning and limitations, not matching wording.
Extend the chapter investigation by evaluating its evidence and proposing a better test.
Problem 1
Answer and explanation
Mean masses are 10,20,30 g; all give 1.00 g/mL. Repeats span.2 g, supporting approximate consistency in this illustrative range. A known calibration mass or independent volume standard would address accuracy; the repeats alone do not exclude common bias. Preserve the original observations, intermediate working and a labeled mechanism. Report the relevant boundary and model assumptions, discuss an alternative explanation, and identify the next useful measurement; do not replace unexpected data with the illustrative record.
Problem 2
Answer and explanation
Mean masses are 10,20,30 g; all give 1.00 g/mL. Repeats span.2 g, supporting approximate consistency in this illustrative range. A known calibration mass or independent volume standard would address accuracy; the repeats alone do not exclude common bias. Preserve the original observations, intermediate working and a labeled mechanism. Report the relevant boundary and model assumptions, discuss an alternative explanation, and identify the next useful measurement; do not replace unexpected data with the illustrative record.
Problem 3
Answer and explanation
Mean masses are 10,20,30 g; all give 1.00 g/mL. Repeats span.2 g, supporting approximate consistency in this illustrative range. A known calibration mass or independent volume standard would address accuracy; the repeats alone do not exclude common bias. Preserve the original observations, intermediate working and a labeled mechanism. Report the relevant boundary and model assumptions, discuss an alternative explanation, and identify the next useful measurement; do not replace unexpected data with the illustrative record.
Problem 4
Answer and explanation
Mean masses are 10,20,30 g; all give 1.00 g/mL. Repeats span.2 g, supporting approximate consistency in this illustrative range. A known calibration mass or independent volume standard would address accuracy; the repeats alone do not exclude common bias. Preserve the original observations, intermediate working and a labeled mechanism. Report the relevant boundary and model assumptions, discuss an alternative explanation, and identify the next useful measurement; do not replace unexpected data with the illustrative record.
Problem 5
Answer and explanation
Mean masses are 10,20,30 g; all give 1.00 g/mL. Repeats span.2 g, supporting approximate consistency in this illustrative range. A known calibration mass or independent volume standard would address accuracy; the repeats alone do not exclude common bias. Preserve the original observations, intermediate working and a labeled mechanism. Report the relevant boundary and model assumptions, discuss an alternative explanation, and identify the next useful measurement; do not replace unexpected data with the illustrative record.
Problem 6
Answer and explanation
Mean masses are 10,20,30 g; all give 1.00 g/mL. Repeats span.2 g, supporting approximate consistency in this illustrative range. A known calibration mass or independent volume standard would address accuracy; the repeats alone do not exclude common bias. Preserve the original observations, intermediate working and a labeled mechanism. Report the relevant boundary and model assumptions, discuss an alternative explanation, and identify the next useful measurement; do not replace unexpected data with the illustrative record.