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Lab 1 - Density of Solids and Liquids
32 Questions
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Lab 1 - Density of Solids and Liquids

Created by
@ColorfulTaylor

Questions and Answers

What is the purpose of the experiment?

  • Densities of water and aqueous NaCl solutions are determined
  • Densities are plotted in dependence of percent mass of NaCl in water
  • Density of an unknown, irregular shaped metal is determined
  • All of the above (correct)

    • What is the formula for density?

    D=m/v

    What is the formula for density of an irregular shaped solid?

    D=mass/(Final volume - initial volume)

    What is an intensive property?

    <p>A physical property that remains the same no matter how much of a substance is present.</p> Signup and view all the answers

    What is an extensive property?

    <p>A property that depends on the amount of matter in a sample.</p> Signup and view all the answers

    If density is intensive, why does it change with temperature and pressure?

    <p>Because volume changes with temperature and pressure.</p> Signup and view all the answers

    What is the difference between precision and accuracy?

    <p>Precision is when multiple trials have similar data, accuracy is when experimental data is correct.</p> Signup and view all the answers

    How do you calculate standard deviation?

    <ol> <li>Calculate mean; 2. Subtract mean from each data point; 3. Calculate difference for each data point; 4. Square the differences; 5. Sum square values; 6. Divide by n-1; 7. Take square root.</li> </ol> Signup and view all the answers

    What is the percent error formula?

    <p>abs(actual-measured)/actual x 100%</p> Signup and view all the answers

    To what precision should you read a 10-mL graduated cylinder?

    <p>To the nearest hundredth of a mL.</p> Signup and view all the answers

    For what did we determine density in the experiment?

    <p>All of the above</p> Signup and view all the answers

    Calculate the density of mercury (in g/mL) if 1.67 kg occupies a volume of 123 mL.

    <p>13.6 g/mL</p> Signup and view all the answers

    Does a change in lab temperature impact the calibration of a balance?

    <p>Systematic error</p> Signup and view all the answers

    Is using a 100 mL graduated cylinder to measure 5.5 mL of solution an example of random or systematic error?

    <p>Random error</p> Signup and view all the answers

    What is it called when you determine your weight by weighing yourself wearing clothes?

    <p>Systematic error</p> Signup and view all the answers

    If you measure the mass of a sample three times using the same balance and get slightly different values, is this a random or systematic error?

    <p>Random error</p> Signup and view all the answers

    In filtration experiments, if small particles pass through the filter paper, is this a systematic or random error?

    <p>Systematic error</p> Signup and view all the answers

    Which of the following is a physical property? (Check all that apply)

    <p>Color</p> Signup and view all the answers

    How would you define density?

    <p>As an intensive physical property</p> Signup and view all the answers

    Which of the following are extensive properties? (Check all that apply)

    <p>Volume</p> Signup and view all the answers

    Convert 10.5 mg to g.

    <p>0.0105 g</p> Signup and view all the answers

    Convert 0.0750 g to mg.

    <p>75.0 mg</p> Signup and view all the answers

    Convert 1.85 g/mL to kg/m³.

    <p>1.85 x 10^3 kg/m³</p> Signup and view all the answers

    Convert 23 cm³ to L.

    <p>0.023 L</p> Signup and view all the answers

    Convert 0.2000 L to mL.

    <p>200.0 mL</p> Signup and view all the answers

    How many significant figures are there in the number 0.05600?

    <p>4 sig figs</p> Signup and view all the answers

    Which is not true about analytical balances?

    <p>Have a greater total capacity than top-loading balances</p> Signup and view all the answers

    True/False: Graduated cylinders are used for the most precise volumetric measurements of liquids.

    <p>False</p> Signup and view all the answers

    What can we infer about the standard deviations of two experimental trials?

    <p>The measurements from the first experiment were more precise.</p> Signup and view all the answers

    If a 0.023211 kg sample of a liquid has a density of 0.9982 g/mL at 25 °C, what would be its volume in mL?

    <p>23.25 mL</p> Signup and view all the answers

    A piece of an unknown metal with a mass of 23.44 g is submerged in 6.02 cm³ of water in a graduated cylinder. The water level increases to 7.23 cm³. Identify the unknown metal.

    <p>Gold</p> Signup and view all the answers

    When disposing of non-hazardous liquids, which of the following statements is correct?

    <p>Non-hazardous chemicals are disposed of into the non-hazardous waste container.</p> Signup and view all the answers

    Study Notes

    Purpose of the Experiment

    • Determine densities of water and aqueous NaCl solutions.
    • Plot densities against percent mass of NaCl to predict density of a 15% NaCl solution.
    • Measure density of an unknown irregular shaped metal for identification.

    Formula for Density

    • Density is calculated using the formula: D = m/v (Density = mass/volume).

    Density for Irregular Shaped Solids

    • Density is found using the formula: D = mass / (final volume - initial volume).

    Properties of Matter

    • Intensive properties, such as density, do not change regardless of the amount of substance present.
    • Extensive properties, such as volume, vary based on the amount of matter.

    Density Changes with Temperature and Pressure

    • Density is affected by temperature and pressure as they alter volume; increased pressure decreases volume and increases density, while increased temperature increases volume and decreases density.

    Precision vs. Accuracy

    • Precision refers to the consistency of multiple trials yielding similar results, while accuracy indicates the correctness of the experimental data.

    Calculating Standard Deviation

    • Steps involve calculating the mean, finding differences from the mean, squaring differences, summing these squares, dividing by n-1, and taking the square root.

    Percent Error Formula

    • Percent error is calculated using: abs(actual - measured) / actual x 100%.

    Graduated Cylinder Measurements

    • A 10-mL graduated cylinder can measure liquid volume to the nearest hundredth of a mL.

    Density Measurement in Experiments

    • Densities determined in the experiment include that of deionized water, an unknown metal, and salt solutions.

    Example Density Calculation

    • Density of mercury is calculated to be 13.6 g/mL for a mass of 1.67 kg occupying 123 mL.

    Errors in Measurements

    • Systematic errors arise from consistent inaccuracies, such as temperature affecting balance calibration.
    • Random errors occur when repeat measurements yield slightly different values, such as measuring the same sample multiple times on the same balance.

    Physical Properties

    • Examples of physical properties include smell, melting point, and color; reactivity with water is not a physical property.

    Density Definition

    • Density is classified as an intensive physical property.

    Extensive Properties

    • Examples include mass, heat, and volume; these properties depend on the quantity of the sample.

    Unit Conversions

    • Conversion examples include:
      • 10.5 mg = 0.0105 g
      • 0.0750 g = 75.0 mg
      • 1.85 g/mL = 1.85 x 10³ kg/m³
      • 23 cm³ = 0.023 L
      • 0.2000 L = 200.0 mL

    Significant Figures

    • 0.05600 contains four significant figures.

    Analytical Balances

    • Analytical balances have higher precision than top-loading balances but generally have a lesser total capacity.

    Graduated Cylinder Usage

    • Graduated cylinders are not the most precise volumetric measuring devices.

    Standard Deviation Inference

    • Lower standard deviation indicates more precise measurements; for example, the first experiment's trials were more precise than the second's.

    Volume Calculation from Mass and Density

    • Volume of a 0.023211 kg sample with density 0.9982 g/mL is calculated to be 23.25 mL.

    Identification of Unknown Metals

    • An unknown metal with mass 23.44 g and water displacement from 6.02 cm³ to 7.23 cm³ is identified as gold.

    Proper Disposal of Non-Hazardous Liquids

    • Non-hazardous liquids should be disposed in designated containers, with rinses handled accordingly: the first two rinses as non-hazardous waste, subsequent rinses may go down the drain.

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    Description

    This quiz focuses on the first lab related to the density of solids and liquids. You will explore the purpose of density experiments and the fundamental formula for calculating density. Understand how to determine densities of various solutions and identify unknown metals based on their density.

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