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Questions and Answers
What is the purpose of the experiment?
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?
What is the formula for density?
D=m/v
What is the formula for density of an irregular shaped solid?
What is the formula for density of an irregular shaped solid?
D=mass/(Final volume - initial volume)
What is an intensive property?
What is an intensive property?
What is an extensive property?
What is an extensive property?
If density is intensive, why does it change with temperature and pressure?
If density is intensive, why does it change with temperature and pressure?
What is the difference between precision and accuracy?
What is the difference between precision and accuracy?
How do you calculate standard deviation?
How do you calculate standard deviation?
What is the percent error formula?
What is the percent error formula?
To what precision should you read a 10-mL graduated cylinder?
To what precision should you read a 10-mL graduated cylinder?
For what did we determine density in the experiment?
For what did we determine density in the experiment?
Calculate the density of mercury (in g/mL) if 1.67 kg occupies a volume of 123 mL.
Calculate the density of mercury (in g/mL) if 1.67 kg occupies a volume of 123 mL.
Does a change in lab temperature impact the calibration of a balance?
Does a change in lab temperature impact the calibration of a balance?
Is using a 100 mL graduated cylinder to measure 5.5 mL of solution an example of random or systematic error?
Is using a 100 mL graduated cylinder to measure 5.5 mL of solution an example of random or systematic error?
What is it called when you determine your weight by weighing yourself wearing clothes?
What is it called when you determine your weight by weighing yourself wearing clothes?
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?
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?
In filtration experiments, if small particles pass through the filter paper, is this a systematic or random error?
In filtration experiments, if small particles pass through the filter paper, is this a systematic or random error?
Which of the following is a physical property? (Check all that apply)
Which of the following is a physical property? (Check all that apply)
How would you define density?
How would you define density?
Which of the following are extensive properties? (Check all that apply)
Which of the following are extensive properties? (Check all that apply)
Convert 10.5 mg to g.
Convert 10.5 mg to g.
Convert 0.0750 g to mg.
Convert 0.0750 g to mg.
Convert 1.85 g/mL to kg/m³.
Convert 1.85 g/mL to kg/m³.
Convert 23 cm³ to L.
Convert 23 cm³ to L.
Convert 0.2000 L to mL.
Convert 0.2000 L to mL.
How many significant figures are there in the number 0.05600?
How many significant figures are there in the number 0.05600?
Which is not true about analytical balances?
Which is not true about analytical balances?
True/False: Graduated cylinders are used for the most precise volumetric measurements of liquids.
True/False: Graduated cylinders are used for the most precise volumetric measurements of liquids.
What can we infer about the standard deviations of two experimental trials?
What can we infer about the standard deviations of two experimental trials?
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?
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?
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.
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.
When disposing of non-hazardous liquids, which of the following statements is correct?
When disposing of non-hazardous liquids, which of the following statements is correct?
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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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