Lab 3: Density and Measurement

Flashcards cover key concepts from Lab 3: density, mass and volume measurement, calculation of density, precision vs. accuracy, measurement practices, and density-based layering of immiscible liquids.

What is density?

Density is the mass of a substance per unit volume, calculated as D = m/V.

How is mass typically measured in the lab?

Mass is measured with an electronic balance.

How is liquid volume accurately measured in the lab?

Very accurate liquid volumes are measured with measuring or volumetric pipettes.

How do you calculate the volume of a solid with a regular shape?

Volume = length × width × height.

How do you determine the volume of an irregular solid?

By displacement: the volume of water displaced equals the volume of the solid.

What equation relates mass, volume, and density?

Density = mass / volume (D = m/V).

Why is it important to repeat measurements in this lab?

To instill confidence in the results and assess precision by averaging multiple trials.

What is precision in measurement?

Precision is how closely repeated measurements cluster together, indicating repeatability.

What is accuracy in measurement?

Accuracy is how close a measurement is to the true or accepted value.

What is an outlier in a data set?

An outlier is a measurement that differs significantly from the others and may be caused by an error; it is often ignored or repeated.

How does density affect layering of immiscible liquids?

Higher-density liquids sink to the bottom, while lower-density liquids float on top.

What determines whether a solid sinks or floats in a liquid?

If the solid's density is greater than the liquid's density, it sinks; if less, it floats.

Why is density useful for identifying substances?

Density is a characteristic property of a substance and helps identify it when compared to known values.

What is the mean (average) used for in this lab?

The mean represents the central value of a set of measurements, illustrating the combined information.

What is Technique Tip 3.1 for adding liquids to a test tube?

Add liquids slowly down the side of the test tube using a long-stem funnel tilted so the stem touches the side.

What are typical densities of common liquids like isopropanol and olive oil?

Isopropanol ≈ 0.781 g/mL; Olive oil ≈ 0.911 g/mL.

What is the approximate density of seawater?

Approximately 1.02 g/mL.

How many trials are used to determine the average density in Parts A and B of the lab?

Three trials (initial measurement plus two repetitions) are used to calculate the mean.

Why should the solid be dried between trials?

Drying prevents residual mass from affecting subsequent measurements, ensuring accuracy.