Density, Viscosity, and Buoyancy 7A investigate and identify properties of fluids including density, viscosity, and buoyancy;

Density, Viscosity, and Buoyancy

7A investigate and identify properties of fluids including density, viscosity, and buoyancy;

What is Viscosity?A measure of a material’s resistance to flow Which substance here has a higher viscosity?

The Ketchup has a high viscosity compared to the water.

Seeing the Effects of Viscosity

Substances with higher viscosity take longer to flow down the ramp.

Viscosity is a measure of the resistance that one layer of liquid experiences when flowing over another layer.

Measuring Viscosity

Viscosity can be measured by how fast a object falls through a liquid.

What about Viscosity vs Density?

Is there a relationship?

Low density indicates low viscosity.

High density indicates high viscosity.

This is not always true.– Think of water and oil. Oil is more viscous but

less dense.– Think of water and corn syrup. Corn syrup is

more viscous but corn syrup has a greater viscosity.

Size and Viscosity

Which molecule would be easier to pour from a bottle?Water or oilWhich would experience more friction? How does that affect viscosity?More friction, greater viscosityLonger molecules have more friction.

Application of Viscosity

Viscosity if the most important property of motor oil.Viscosity depends on temperature –

Increase temperature will decrease the viscosity of the material.

In the winter you need a lower viscosity oil so the

oil will flow better.

In the summer, you need a higher viscosity oil so during the higher summer temperatures it will not

flow too fast. (If an oil is too thin it does not adhere to the surfaces and lubricate the moving parts.)

Motor Oil

SAE – Society of American Engineers

The viscosity of oil tends to decrease as it heats up (oil break downs)

Big molecules to little molecules.

What does 10 W 30 mean?

Viscosity Index- Cold

Engine

Meets viscosity requirements for winter (low temp)

Viscosity index – hot engine

Viscosity Review

Viscosity is the resistance to flow. For example pancake syrup flows more

slowly than water. We say the pancake syrup is more viscous. Ketchup and molasses are good

examples of “viscous” materials.Viscosity is the most important property of motor oil.Increase temperature will decrease viscosity of a material.

Density Density is a relationship between mass of a substance and its volume.

Water has a density of 1

More dense substances sink and less dense objects float

If you add salt to water it becomes more dense

If you heat a substance it becomes less dense.

D = M

V

DensityAs you heat a substance its molecules move farther apart and the substance becomes less dense.

Ice Liquid Gas

Buoyancy

The upward force on a body immersed or partly immersed in a fluid.

1. What is the density at 20C of 12.0 milliliters of a liquid that has a mass of 4.05 grams?

A. 0.338 g/mL

B. 2.96 g/mL

C. 16.1 g/mL

D. 48.6 g/mL

Powerful Plankton

The U.S. Naval Research Laboratory has created an experimental marine fuel cell that could produce enough electricity to power ocean-monitoring devices. This fuel cell runs on seawater and sediment, with the help of plankton. Some plankton on the surface of ocean sediments use dissolved oxygen to break down organic matter, releasing energy; this is an aerobic process. The plankton in the deeper sediments break down organic matter without using oxygen; this is an anaerobic process. These two processes create a difference in voltage between the surface of the sediment and the sediment farther down in the seabed. The voltage difference can be used to produce electricity—up to 5.0V; 1.0 – 2 watts of power. Energy supplied by this type of fuel cell can be obtained as long as there is organic matter in the sediment.

2. What is the mass of a 500.00 mL sample of seawater with a density of 1.025 g/mL?

A. 487.8 g

B. 500.0 g

C. 512.5 g

D. 625.0 g

3. Which of the following objects will float on water?

A. [Option 1]

B. [Option 2]

C. [Option 3]

D. [Option 4]

4. Students in a chemistry lab measure the time it takes four different 100 mL solutions to pass through a hole in the bottom of a cup. Which of the following properties of the solutions is most likely being measured?

A. Buoyancy

B. Mass

C. Viscosity

D. Volume

Watersheds

The San Antonio–Nueces Coastal Basin, shown in the map below, consists mainly of flatland. The soil in the area is mostly sandy and porous. Rainfall that collects in this area drains into the Gulf of Mexico by a series of waterways.

The San Antonio–Nueces Coastal Basin is one of more than 20 major watersheds in Texas. A watershed is a geographic area that drains water collected on its surface. Watersheds provide a way for water to move from areas of higher elevation to areas of lower elevation. Sediment and dissolved materials are also moved to lower elevations.

Rivers and streams form a general pattern within a watershed. The map shows this general pattern

within the San Antonio–Nueces Coastal Basin. This type of pattern is called a dendritic pattern and can be observed in many natural structures, including the network of nerves in the human nervous system and branching patterns in trees.

Watersheds can change as the geography and other features of an area change. Some of the causes of change are more obvious than others. For example, the clearing of wooded areas for the construction of buildings may change the way rainfall collects and drains from an area.

5. Use the information on the previous page to answer this question. A sample of water from a stream has a greater density than a sample of distilled water. Which is the best explanation for the difference in density?

A. Streams have kinetic energy.

B. Distilled water has a neutral pH.

C. Streams can contain dissolved salts.

D. Distilled water can contain dissolved gases.

6. From the data in the table, what would be the mass of a 3.0 L sample of water collected from Gunnison Bay?

A. 2515 g

B. 3171 g

C. 3579 g

D. 4193 g

7. A diet cola and a regular cola in identical cans are each placed in separate beakers containing water. Which of the following conclusions is the best for the experiment shown above?

A. The diet cola is less dense than the regular cola.

B. The diet cola has fewer calories than the regular cola.

C. There is more buoyant force on the can of diet cola than on the regular cola.

D. There is more liquid in the can of diet cola than in the regular cola.