Density and Specific Gravity Quiz
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Questions and Answers

What is the specific gravity of the oil if a plummet weighs 12.64 g in air, 9.12 g in oil, and 8.57 g in water?

  • 0.755
  • 0.865 (correct)
  • 0.932
  • 1.045

How much would 50 mL of a liquid with a specific gravity of 1.2 weigh?

  • 50 g
  • 45 g
  • 55 g
  • 60 g (correct)

If 3620 mL of alcohol has a specific gravity of 0.820, what is its weight in grams?

  • 2970 g
  • 2968 g (correct)
  • 3000 g
  • 3620 g

What formula would be used to calculate grams given milliliters and specific gravity?

<p>Grams = Milliliters x Specific gravity (C)</p> Signup and view all the answers

What is the volume of 492 g of nitric acid with a specific gravity of 1.40?

<p>351 mL (A)</p> Signup and view all the answers

Which of the following best describes a practical application of specific gravity in pharmaceuticals?

<p>Converting weight of an ingredient to volume. (C)</p> Signup and view all the answers

What is the specific gravity of water considered to be?

<p>1.0 (A)</p> Signup and view all the answers

Why is specific gravity important in urinalysis?

<p>To characterize the concentration of urine. (B)</p> Signup and view all the answers

If a liquid has a specific gravity less than 1, how does it compare to water?

<p>It is lighter than water. (B)</p> Signup and view all the answers

In calculating specific gravity, what does the weight of displaced liquid represent?

<p>The weight of equal volumes of liquids. (B)</p> Signup and view all the answers

What is the formula used to calculate density?

<p>Density = mass / volume (C)</p> Signup and view all the answers

What unit is specific gravity measured in?

<p>dimensionless (C)</p> Signup and view all the answers

If a substance has a specific gravity of 0.8, what can be inferred about its density relative to water?

<p>It is lighter than water. (C)</p> Signup and view all the answers

Which of the following is considered the standard substance for specific gravity calculations of liquids and solids?

<p>Water (C)</p> Signup and view all the answers

At what temperature is specific gravity typically standardized for most substances, according to the USP?

<p>25°C (A)</p> Signup and view all the answers

Which of the following measurements would give a specific gravity of 1 for a substance?

<p>10 g substance in 10 mL water (C)</p> Signup and view all the answers

When comparing a liquid's density to water, what does a density of 1 g/mL imply?

<p>The liquid has the same density as water. (B)</p> Signup and view all the answers

Which of the following substances is used as the standard for calculating the specific gravity of gases?

<p>Hydrogen (A)</p> Signup and view all the answers

What is the normal specific gravity range of urine in adults with normal fluid intake?

<p>1.010 to 1.025 (B)</p> Signup and view all the answers

Which condition is indicated by a higher-than-normal specific gravity of urine?

<p>Glucosuria (A)</p> Signup and view all the answers

What effect does age generally have on the specific gravity of urine?

<p>It decreases (C)</p> Signup and view all the answers

Which of the following indicates dilute urine?

<p>Specific gravity of 1.005 (C)</p> Signup and view all the answers

What is the significance of urine specific gravity in clinical settings?

<p>It indicates the degree of hydration and concentration of urine (C)</p> Signup and view all the answers

In newborns, what is the typical range of urine specific gravity?

<p>1.001 to 1.020 (B)</p> Signup and view all the answers

Which method is commonly used to determine urine specific gravity in modern clinical laboratories?

<p>Refractive index method (A)</p> Signup and view all the answers

Which of the following factors may lead to a low specific gravity of urine?

<p>Excessive water intake (C)</p> Signup and view all the answers

What might a specific gravity of urine above 1.025 indicate?

<p>Excessive water loss (C)</p> Signup and view all the answers

Which of these conditions could NOT result in low specific gravity urine?

<p>Glucosuria (A)</p> Signup and view all the answers

What is the specific gravity of a liquid that weighs 601 g and displaces the weight of 473 g of water?

<p>1.27 (B)</p> Signup and view all the answers

Why is specific gravity considered a dimensionless quantity?

<p>It has no units associated with it. (A)</p> Signup and view all the answers

What measurements are necessary to calculate the specific gravity using a pycnometer?

<p>Weight of water and weight of unknown liquid. (D)</p> Signup and view all the answers

If a substance has a specific gravity of 0.78, what can be inferred about its density compared to water?

<p>It is less dense than water. (B)</p> Signup and view all the answers

What principle underlies the calculation of specific gravity using the displacement method?

<p>Archimedes' principle. (B)</p> Signup and view all the answers

What is the equivalent weight of 54.96 mL of water in grams?

<p>54.96 g (D)</p> Signup and view all the answers

Which method is specifically mentioned for determining specific gravity in a laboratory setting?

<p>Pycnometer or specific gravity bottle. (B)</p> Signup and view all the answers

How is the density of a substance expressed compared to the specific gravity?

<p>Density is a variable measurement based on units, while specific gravity is constant. (D)</p> Signup and view all the answers

What is the specific gravity of water when measured in any conditions?

<p>1 (C)</p> Signup and view all the answers

Which of the following is true about the density of substances at different conditions?

<p>Density increases with increased pressure. (A), Density decreases at higher temperatures. (C)</p> Signup and view all the answers

Flashcards

What is density?

Density is the measure of how much mass is packed into a given volume of a substance. It tells us how dense or compact the substance is.

How do we express density?

Density is typically expressed in grams per cubic centimeter (g/cc) or grams per milliliter (g/mL).

How do you calculate density?

To calculate density, you divide the mass of the substance by its volume. Equation: Density = Mass / Volume.

What is specific gravity?

Specific gravity is a ratio that compares the weight of a substance to the weight of an equal volume of water (or another standard substance like hydrogen for gases).

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How do we express specific gravity?

Specific gravity is expressed as a decimal number with no units. It's simply a ratio of weights.

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How do you calculate specific gravity?

To calculate specific gravity, you divide the weight of the substance by the weight of an equal volume of water (or the standard substance). Equation: Specific gravity = Weight of substance/Weight of equal volume of water.

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What does specific gravity tell us about a substance?

Substances with a specific gravity less than 1 are lighter than water and will float. Substances with a specific gravity greater than 1 are heavier than water and will sink.

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Why is specific gravity important?

Specific gravity is a valuable tool to convert between weight and volume, aiding in various applications like mixing solutions or determining container sizes.

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What is the standard temperature for measuring specific gravity?

Specific gravity is measured at a standard temperature, typically 25°C for liquids and solids, and 15.56°C for alcohol.

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What is a pycnometer?

A pycnometer is a special flask used to measure the volume of a substance accurately. It's used to determine specific gravity.

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Density

A measure of the mass of a substance per unit volume.

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Specific Gravity

The ratio of the density of a substance to the density of a reference substance, usually water.

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Constant value for Specific Gravity

A specific density value that does not change with the units of measurement used.

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Density of Water

The density of water at standard conditions is 1 g/mL.

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Specific Gravity of Water

The specific gravity of water is always 1.

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Specific Gravity Calculation: Known Weight and Volume

A method for calculating specific gravity of liquids using the weight and volume of both the unknown liquid and water.

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Pycnometer

A special glass bottle used to determine specific gravity of liquids by measuring the weight of the bottle filled with water and the unknown liquid.

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Displacement or Plummet Method

A method for calculating specific gravity of liquids based on Archimedes' principle, using the weight of the liquid displaced by an object.

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Archimedes' Principle

Archimedes' principle states that an object immersed in a liquid will experience an upward buoyant force equal to the weight of the liquid displaced.

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Applications of Specific Gravity

Specific gravity is used in various fields such as chemistry, pharmaceuticals, and engineering to compare the densities of liquids.

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How is specific gravity useful in pharmacy?

Specific gravity helps convert the weight of a substance to volume or vice versa.

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What other applications does specific gravity have in pharmacy?

Specific gravity helps calculate the equivalent strength of a preparation based on either weight or volume.

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How is specific gravity used in automated pharmaceutical equipment?

Specific gravity plays a crucial role in determining the weight of components in total parenteral nutrition (TPN) admixtures.

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How is specific gravity used in clinical settings?

Specific gravity is a key factor analyzed in urine tests, providing information about the kidneys' ability to concentrate urine.

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At what temperature is specific gravity usually measured?

Specific gravity is measured at a standard temperature, typically 25°C for liquids and solids, and 15.56°C for alcohol.

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How is specific gravity expressed?

Specific gravity is a unitless quantity expressed as a decimal number.

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What is specific gravity of urine?

A measure of the concentration of particles in urine, reflecting the body's hydration level.

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What is the normal specific gravity of urine in adults?

A range of 1.010 to 1.025, typically, indicating normal hydration.

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How does specific gravity of urine change with age?

It usually decreases with age.

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What is the normal specific gravity of urine in newborns?

A range of 1.001 to 1.020.

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What does a high specific gravity of urine indicate?

High specific gravity indicates concentrated urine, possibly due to dehydration, excess waste products, or conditions like glucosuria or proteinuria.

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What does a low specific gravity of urine indicate?

It indicates dilute urine, possibly due to diabetes insipidus, kidney disease, or increased fluid intake.

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How is specific gravity of urine measured in a clinical setting?

A comprehensive urinalysis, usually performed with automatic equipment.

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Why is specific gravity of urine clinically important?

It's a valuable tool to assess hydration status and detect potential health problems.

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Why does specific gravity of urine change?

It's a direct result of the concentration of dissolved particles in the urine.

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What does specific gravity of urine reflect?

It's the ability of the kidney to concentrate urine and is important for regulating body water balance.

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Study Notes

Density and Specific Gravity

  • Density is mass per unit volume at a constant temperature and pressure.
  • Density is measured in grams per cubic centimeter (g/cc) or grams per milliliter (g/mL) in the CGS system.
  • In SI units, density can be expressed as kilograms per cubic meter.
  • Density is calculated by dividing mass by volume.
  • Example: If 10 mL of sulfuric acid weighs 18 grams, its density is 1.8 g/mL.

Specific Gravity

  • Specific gravity (sp gr) is a ratio of the weight of a substance to the weight of an equal volume of a standard substance at the same temperature.
  • For liquids and solids, water is the standard.
  • For gases, hydrogen is the standard.
  • Specific gravity is a dimensionless quantity.
  • Specific gravity is calculated by dividing the weight of a substance by the weight of an equal volume of water.
  • Example: If 10 mL of sulfuric acid weighs 18 g, and 10 mL of water weighs 10 g, the specific gravity of the acid is 1.8.

Density vs Specific Gravity

  • Density is a concrete number, specific gravity an abstract number.
  • Density varies with the unit of measurement.
  • Specific gravity is constant under controlled conditions.
  • Density of water can be expressed as 1 g/mL, 1000 g/L, or 62.5 lb/cu ft.
  • Specific gravity of water is always 1.

Calculating Specific Gravity (Known Weight and Volume Methods)

  • Specific gravity = weight of substance / weight of equal volume of water
  • Example 1: If 54.96 mL of oil weighs 52.78 g, its specific gravity is 0.9603.
  • Example 2: If a pint of a liquid weighs 601 g, and a pint of water weighs 473 g, its specific gravity is 1.27.

Pycnometer or Specific Gravity Bottle

  • A pycnometer is a special glass bottle for determining specific gravity.
  • It has a volume ranging from 1 to 50 mL.
  • A pycnometer is weighed empty, then filled with water, then filled with the substance and weighed again.
  • Example: A 50 mL pycnometer weighs 120 g empty, 171 g when filled with water, and 160 g when filled with an unknown liquid. The specific gravity of the liquid is 0.78

Displacement or Plummet Method

  • Based on Archimedes' principle, a body immersed in a fluid displaces an equal volume of fluid.
  • A plummet (a weighted object) is weighed in air, water and a liquid of unknown density.
  • The difference in weight corresponds to the weights of displaced liquid.
  • Example: A glass plummet weighs 12.64 g in air, 8.57 g in water, and 9.12 g in oil. The specific gravity of the oil is 0.865.

Using Specific Gravity in Calculations

  • Specific gravity is a factor that helps determine how much heavier or lighter a substance is compared to water (water's specific gravity is 1).
  • If a liquid's specific gravity is 1.2, it weighs 1.2 times as much as an equal volume of water.
  • Example: 50 mL of a liquid with a specific gravity of 1.2 would weigh 60 grams (50 mL x 1.2 = 60 g)

Calculating Weight, Knowing Volume and Specific Gravity

  • Grams = Milliliters x Specific gravity
  • Example: What is the weight (in grams) of 3620 mL of alcohol with a specific gravity of 0.820? The answer is 2968 grams

Calculating Volume, Knowing Weight and Specific Gravity

  • Milliliters = Grams / Specific gravity
  • Example: What is the volume (in milliliters) of 492 g of nitric acid with a specific gravity of 1.40? The answer is 351 mL.

Pharmaceutical Applications

  • Specific gravity converts weight to volume and vice-versa.
  • It calculates equivalent strength based on weight or volume.
  • Pharmacists use it in automated equipment (TPN admixtures).
  • It's used to determine weights of components (e.g., dextrose, amino acids, water) in large volume liquid mixtures.

Clinical Application (Urinalysis)

  • Specific gravity is crucial in urinalysis.
  • Normal adult urine ranges from 1.010 to 1.025.
  • Specific gravity decreases with age.
  • Newborn urine ranges from 1.001 to 1.020.
  • High specific gravity indicates concentrated urine, potential excess waste products, electrolytes, glucose or protein.
  • Low specific gravity suggests dilute urine, possibly from diabetes insipidus, renal disease, increased fluid intake, IV hydration, etc.
  • Modern labs use refractive index methods to determine specific gravity in comprehensive urinalysis.

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Test your understanding of density and specific gravity concepts. This quiz covers definitions, calculations, and examples relevant to both topics. Perfect for students learning about the physical properties of substances.

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