Density and Buoyancy of Fluids

Flashcards covering the definition of density, particle theory, calculations, graphical comparison, and sink-or-float behaviors of fluids and solids.

How is density defined in terms of mass and volume?

Density is defined as the amount of mass contained in a given volume, describing how closely packed together the particles are in a substance.

Why does warm water float on top of colder water in a lake during the summer?

Warm water has a lower density than cold water, which causes it to float on the colder, denser water below.

According to the particle theory, what causes a substance's density to decrease as it warms up?

When energy is added, particles move faster and farther apart, causing the volume to increase while the number of particles stays the same.

Generally, in which state of matter does a substance have the greatest density?

A substance generally has a greater density in its solid state than in its liquid or gas states.

Based on the molecular diagrams shown, why does solid ice float on liquid water instead of sinking?

Unlike most substances, water molecules in ice arrange into an open crystalline lattice that takes up more space, making solid ice less dense than liquid water.

What is the formula for calculating density?

$$\text{Density } (D) = \frac{\text{mass } (m)}{\text{Volume } (V)}$$

What standard measurement units are commonly used for the densities of liquids, gases, and solids?

Liquids are measured in grams per milliliter ($\text{g/mL}$), gases in kilograms per litre ($\text{kg/L}$), and solids in grams per cubic centimeter ($\text{g/cm}^3$).

What is the density of an oil sample with a mass of $1.75\,\text{g}$ and a volume of $2.0\,\text{mL}$?

$0.88\,\text{g/mL}$ ($D = \frac{1.75\,\text{g}}{2.0\,\text{mL}} = 0.88\,\text{g/mL}$)

What is the density of a $17\,\text{mL}$ sample of gasoline with a mass of $13\,\text{g}$?

Approximately $0.76\,\text{g/mL}$ ($\frac{13\,\text{g}}{17\,\text{mL}} \approx 0.76\,\text{g/mL}$)

What is the density of a $3.5\,\text{cm}^3$ glass marble that has a mass of $8.5\,\text{g}$?

Approximately $2.43\,\text{g/cm}^3$ ($\frac{8.5\,\text{g}}{3.5\,\text{cm}^3} \approx 2.43\,\text{g/cm}^3$)

Which has a greater density: $6.0\,\text{mL}$ of rubbing alcohol with a mass of $3.0\,\text{g}$, or a $9.0\,\text{cm}^3$ block of wood with a mass of $5.6\,\text{g}$?

The block of wood has the greater density ($\approx 0.62\,\text{g/cm}^3$ for wood compared to $0.50\,\text{g/mL}$ for rubbing alcohol).

On a mass-versus-volume graph, how does line slope indicate whether a substance will float or sink in water?

A substance with a steeper slope than water will sink, while a substance with a gentler slope than water will float.

Based on the provided graph, which substances have a lower density than rubbing alcohol (isopropyl)?

Gasoline and wood (pine).

If gasoline and vegetable oil are poured into the same container, which substance will sit on top?

Gasoline will be on top because it has a lower density than vegetable oil.

According to the density graph of common substances, what is the mass of $30\,\text{mL}$ of aluminum?

Approximately $81\,\text{g}$

What happens to an object placed in a fluid if the object's density equals the fluid's density?

The object will hover in place within the fluid.

Based on the density column shown in the diagram, list the three liquids in order from least dense to most dense.

Oil is the least dense, water is in the middle, and syrup is the most dense.

In the density column jar containing oil, water, syrup, a cork, a plastic block, and a grape, which item has the lowest density overall?

The cork has the lowest density because it floats on top of the oil.