Fluids are essential to many industrial processes and form the basis of hydraulic and pneumatic devices. Any substance that flows is considered to be a fluid. This includes such things as water, shampoo, sunscreen, and honey. Even gases, such as air, can be classified as fluids. You will investigate the properties of fluids and the impacts of technology based on the properties of fluids.


What is a Fluid?
A fluid is anything that flows. Do solids flow? Do liquids…do gases? Both liquids and gases flow from one place to another so they are both classified as fluids.

Warning, Fluids Kill!
How do fluids have negative impacts on people, animals, and plants?

Floods kill people, plants, and animals every year. Natural disasters involving fluids such as tornadoes, hurricanes, and floods kill and change lives forever. Some of these natural disasters may be brought on by human interference with natural systems. An example of this occurs when humans change water courses or water levels in an area - for instance when they build a dam.

The Impact of Fluid Spills
There are so many hazardous chemicals being used in homes, gardens, and businesses today that you would have a hard time keeping track of them all. Many homes and businesses realize that these chemicals are health hazards and are decreasing or eliminating their use, but others aren't.

How many hazardous fluids do you have in your home?

Chemical Hazards
Visit the Chemical Hazards website and identify each class of chemicals and provide an example of each.

A-Compressed Gas
Gases placed under pressure or chilled to contain it in a cylinder
Propane for a BBQ

Helium for balloons

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The Home Hazardous Fluid Hunt
1. Look for hazardous fluids in one of the following areas of your home:
  • where you store cleaning supplies;
  • where you store laundry supplies;
  • where you store paint supplies;
  • where you keep your gardening supplies;
  • where you store car, lawnmower, or chainsaw supplies.

2. Make a list of all the fluids (liquids and gasses) in these areas.
3. Identify the ways each fluid is a risk to human health and/or the environment (e.g. corrosive, poisonous, flammable, or explosive).
4. Make a list of some of the ingredients that you believe are hazardous. Use the Internet to find out how.

Disaster! Assignment
A truck filled with a hazardous chemical has just jackknifed on the highway and is leaking onto the road and down the grassy hill beside it. Some of the fluid has already reached the stream at the bottom of the hill.

1. Identify the immediate dangers of this situation.
2. Identify the long-term effects of this situation on human health.
3. Identify the long-term effects of this situation on the environment.
4. Use the Internet to find information on the procedures that should be used to clean this spill.

Oil Spills
The Effects of Oil on Wildlife
Oil Spills Impact on the Ocean
Oil Spill Worksheet

RAFT Writing
Choice #1 You are a bird that lives near the water. Create a picture book that will inform young students about the dangers of oil spills.

Choice #2 You are the ocean. Write a letter to an oil company explaining the effects of oil spills on your health.

How can hazardous fluid spills be avoided?
Brainstorm a list of all the ways to prevent harmful fluid spills. Remember to think beyond simply listing different ways of dealing with harmful fluids.


Fluids in Your Body
In the Cells Unit, you studied the importance of your blood to your life. Your blood transports all the nutrients, including oxygen, and all the waste products, including carbon dioxide, to and from all the cells of your body to keep you alive. Your life depends on this fluid. Problems with this fluid, or the components of this fluid, can affect your health drastically. Most multicellular organisms have transport systems similar to yours to keep them alive and healthy.

Water is another fluid that is essential to your life and the lives of most other living things on the planet. Without water, cells would not be able to perform their functions properly and would eventually die.

Fluids that Make Your Life Easier
Gasoline is a fluid that has made the lives of humans easier for over a century by providing a way to travel that is faster and easier than it was in the past. Gasoline comes from crude oil that is taken from the ground. Another product that is taken from crude oil is oil. Oil is a viscous fluid that protects engine parts as they slide beside each other while the engine works. If you compare how easily your hands slide on one another when they are dry compared to when they are wet or oily, you will get the idea of how oil decreases friction. There are much more ways that fluids make your life easier.

In order to understand the usefulness of fluids, you need to know more about them. You already know that, in general, solids are denser than liquids and liquids are denser than gasses. You may also know that density is related to buoyancy.

Density and Buoyancy

Why does a substance float in some fluids, but sink in others?

• If the density of a substance is greater than the density of the fluid, the substance will sink.
• If the density of a substance is less than the density of the fluid, the substance will float.
• If the density of a substance is the very same as the density of a fluid, the substance will "hover" in place.

If all metals have a greater density than water, how is it possible for metal boats to float on water? The answer is that a boat consists of more than just metal. If you consider the density of the air inside the boat and the density of all the objects in the boat, you would find that the combined density of all parts of the boat is less than the density of the water.

A hot air balloon filled with air the same temperature as the air around it will not float because its density is the same as everything around it. Hot air balloons float when they are filled with hot air because hot air is less dense than cooler air. There is also a reason why hot air balloons remain inflated as they float through the sky even though they have a big hole in the bottom of them. This reason is explained by Pascal's Law: A force applied to a fluid is distributed equally throughout the entire fluid.

Viscosity is a measurement of a fluid's resistance to flow. You have had experiences working with many fluids and know some of the differences between their flow rates, or how fast they flow.

Factors Affecting Viscosity
Some of the factors that affect viscosity: density, shape, and temperature.

Factors Affecting Density
Temperature affects density as well as viscosity. Fluids heat up they expand. This expansion means that there is the same number of particles in a larger space so the density of the fluid is decreased. Pressure also affects density.

A substance can have different densities, depending on its temperature. For example, imagine swimming in a lake on a hot summer day. The water on the surface of the lake is noticeably warmer than the water below it. The warm water floats on the cold water because it has a lower density than that of cold water.

You may have noticed that the air in a room is warmer toward the ceiling and cooler toward the floor. The warmer air has a lower density, so it rises above the cooler, higher density air along the floor.

According to the particle theory, particles in a substance move more quickly when energy is added. As a substance warms up, the particles move faster and farther apart. This causes the volume to increase even though the number of particles stays the same. With the same number of particles in a larger volume, the density decreases. A substance generally has a greater density in its solid state than in its liquid state and gas state. One exception to this is water. The particles in water move slightly farther apart as the water freezes, so ice is less dense that liquid water.

Calculating Density
Density is the ratio of mass to volume. You can calculate the density of a substance by dividing its mass by its volume.

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1. A 15-mL sample of gasoline has a mass of 11 g. What is the density of the gasoline?
2. What is the density of a 2.5 cm3 glass marble that has a mass of 7.5 g?
3. The mass of 5.0 mL of rubbing alcohol is 4.0 g. The mass of an 8.0 cm3 block of wood is 5.6 g. Which of these materials has the greater density?

Hydraulics and Pneumatics

Explain Hydraulics

Many of the machines in your world use hydraulics or pneumatics. The compression characteristics of fluids have been used for the benefit of humans. Both air and liquids - most often oil - are used to do work that was once performed by humans. So, just how useful have they been? The use of pressurized air is called pneumatics (pronounced new-ma-ticks) while the use of liquids is called hydraulics. You are probably at least somewhat familiar with these terms.

Gasses and liquids do similar jobs in pneumatics and hydraulics, but the pressure involved is different, and the reasons each is used are different. Often it is important that there be no source of spark or fire in a work area where there are explosive gasses. That is why pneumatics was developed. Pneumatic systems minimize electrical use in a work area. Buses use pneumatic doors because they work at a lower pressure and at a larger temperature range than hydraulic devices.