This worksheet provides answers and detailed explanations to common density problems, helping chemistry students solidify their understanding of this fundamental concept. Density, a crucial property in chemistry, represents the mass of a substance per unit volume. Understanding density calculations is essential for various applications, from identifying unknown substances to solving stoichiometry problems.
Understanding Density: Mass, Volume, and the Relationship
Before diving into the answers, let's quickly review the fundamental density equation:
Density (ρ) = Mass (m) / Volume (V)
This equation tells us that density is directly proportional to mass and inversely proportional to volume. A higher mass in the same volume results in higher density, while a larger volume with the same mass results in lower density. Remember that units are crucial! Common units for density include g/cm³, g/mL, and kg/m³.
Density Worksheet Problems and Solutions
This section provides solutions to common density problems encountered in chemistry worksheets. We'll cover various scenarios and explain the step-by-step approach to solving them. Remember to always show your work and clearly state your units.
Problem 1: Calculating Density
Question: A sample of gold has a mass of 96.5 g and a volume of 5.00 cm³. Calculate the density of gold.
Answer:
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Identify known variables: Mass (m) = 96.5 g, Volume (V) = 5.00 cm³
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Apply the density equation: ρ = m/V
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Substitute values and solve: ρ = 96.5 g / 5.00 cm³ = 19.3 g/cm³
Therefore, the density of gold is 19.3 g/cm³.
Problem 2: Calculating Mass
Question: A block of aluminum has a density of 2.70 g/cm³ and a volume of 10.0 cm³. What is the mass of the aluminum block?
Answer:
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Rearrange the density equation to solve for mass: m = ρ * V
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Substitute values and solve: m = 2.70 g/cm³ * 10.0 cm³ = 27.0 g
Therefore, the mass of the aluminum block is 27.0 g.
Problem 3: Calculating Volume
Question: A liquid sample has a mass of 55.0 g and a density of 0.80 g/mL. What is the volume of the liquid sample?
Answer:
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Rearrange the density equation to solve for volume: V = m/ρ
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Substitute values and solve: V = 55.0 g / 0.80 g/mL = 68.75 mL
Therefore, the volume of the liquid sample is 68.75 mL.
Problem 4: Identifying an Unknown Substance
Question: A sample with a mass of 25.0 g and a volume of 10.0 mL has a density of 2.5 g/mL. Using the table below, identify the unknown substance.
| Substance | Density (g/mL) |
|---|---|
| Ethanol | 0.79 |
| Water | 1.00 |
| Aluminum | 2.70 |
| Iron | 7.87 |
Answer: The density of the unknown substance is 2.5 g/mL. Comparing this value to the table, we see that it is closest to the density of Aluminum (2.70 g/mL). Note: There might be some error in experimental density measurement.
Problem 5: Density and Temperature
Question: Explain how temperature affects the density of a substance.
Answer: Temperature typically affects the density of a substance. As temperature increases, most substances expand, increasing their volume. Since density is mass/volume, an increase in volume with constant mass leads to a decrease in density. However, there are exceptions, particularly with water near its freezing point.
Beyond the Basics: Advanced Density Concepts
While these problems cover fundamental density calculations, remember that density applications extend to more advanced concepts in chemistry, including:
- Specific Gravity: A dimensionless quantity representing the ratio of a substance's density to the density of a reference substance (usually water).
- Archimedes' Principle: Used to determine the buoyancy of objects based on their density relative to the surrounding fluid.
- Stoichiometry: Density plays a crucial role in converting between mass, volume, and moles in stoichiometric calculations.
This comprehensive guide provides a strong foundation for understanding density in chemistry. By practicing these problems and exploring further applications, students can build a solid understanding of this critical concept. Remember to consult your textbook and instructor for additional resources and clarification.
