Question

Which is less dense: high density polyethylene (HDPE) or water? How do you know?

Short answer

HDPE is less dense than water, as its density is 0.93-0.97 g/cm³ compared to water's 1 g/cm³.

Step-by-step solution

Understand Density

Density is defined as mass per unit volume. It is commonly expressed in grams per cubic centimeter (g/cm³) or kilograms per cubic meter (kg/m³).

Density of Water

The density of water is well established as approximately 1 g/cm³ at 4°C. This is often used as a reference point in comparing densities.

Density of High Density Polyethylene (HDPE)

HDPE has a density range of approximately 0.93 to 0.97 grams per cubic centimeter (g/cm³). This means it is less dense than water.

Compare Densities

Compare the density of HDPE (0.93 to 0.97 g/cm³) with that of water (1 g/cm³). Since the density of HDPE is less than that of water, HDPE will float in water.

Key concepts

Density Comparison

Density, one of the fundamental physical properties of a substance, provides insight into how mass is distributed within a given volume. Comparing densities allows us to predict the behavior of materials in various scenarios. For example, if we compare high density polyethylene (HDPE) and water, we look at their respective densities to understand floatation behavior.
HDPE, with a density ranging between 0.93 to 0.97 g/cm³, is less dense than water, which has a density of approximately 1 g/cm³.
Because HDPE's density is lower, it will float on water. This is a practical demonstration of density principles in action, highlighting how materials with a lower density than a fluid will naturally stay afloat or rise through it.

• HDPE density: 0.93 - 0.97 g/cm³
• Water density: 1 g/cm³
• HDPE floats on water due to lower density

Physical Properties

Physical properties of materials, like density, texture, color, and melting point, help describe and categorize substances without altering their chemical structure. Density is noteworthy as it influences how materials interact with their surroundings.
For HDPE, a widely used plastic, its physical property of density impacts its application significantly. Being less dense than water makes HDPE valuable for products that need to be buoyant, like containers that won't sink.
Moreover, density influences the strength-to-weight ratio, which is essential in engineering and design. Thus, understanding the physical properties, especially density, aids in choosing the right material for specific needs.

• Density impacts floatation and application
• Buoyant materials are useful in water-based applications
• Understanding physical properties guides material selection

Material Science

Material science delves into the characteristics and engineering of materials, focusing on their physical and chemical properties. A core aspect of material science is designing and improving materials to fit specific purposes by understanding properties like density.
For instance, the study of HDPE in material science is centered on its lightweight nature due to its low density, making it suitable for a plethora of applications like packaging, piping, and even toys. Research into the densities of materials enables improvements in buoyancy, strength, and flexibility.
By mastering the science behind these materials, industries can innovate and create products that are not only efficient but also sustainable and economically viable.

• Material science combines physical and chemical property understanding
• Density studies lead to improved material applications
• Innovative materials promote sustainable solutions