Flour is an ingredient that is found in most kitchens and used regularly for baking and cooking. Consequently, it is considered safe, and people do not regard the potential hazards. In reality, flour and dust explosions are extremely dangerous, and reducing the risk of such an explosion is a major concern to the agriculture and food processing industries.
The purpose of this demonstration/activity is to illustrate the importance of being aware of potentially harmful situations and practices in the workplace. In particular, the dustiness of a material can affect the nature of chemical reaction, affecting a safe working environment.
How does it work?
Flour is combustible. When sitting as a stable pile the fuel (flour) is more connected to other flour particles than oxygen particles. As dust, each dust particle is surrounded by oxygen particles. This supports the combustion of the flour particle. As each particle moves through the flame, the combustion moves with the particles. Flour explosions tend to be connected to the movement of flour through air. The source of ignition is often discovered to be a static discharge.
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The boiling point of a liquid depends on the external air pressure. When water is placed under vacuum, the boiling point decreases and the water boils. Boiling, however, is an endothermic process—as the water boils, the temperature decreases, and the water soon freezes!
In this demo, pressure changes cause a sample of acetone freezes while still boiling.
Click here for the complete instructions, courtesy of Flinn Scientific
Image courtesy of Steve Spangler
This demo models how convection occurs in the atmosphere and hydrosphere by showing what happens at the interface of a hot fluid and a cold fluid. This simulates what happens when cold and hot air masses meet, as well as why/how the ocean regulates climate. Continue reading
In this demonstration, students will see a model showing that antibodies bind to antigens as an immune response to foreign invaders. Continue reading
Most people don’t need matches, safety glasses and hydrogen gas to crack open an egg. But then again, Steve always finds the most unusual method to do the simplest things. Don’t try this at home. Continue reading
This is a simple, yet extremely effective model of human lungs. Students are able visualize how the lungs, thoracic cavity and diaphragm work together to facilitate inhalation and exhalation. Continue reading
In this demo, two polyethylene strips are charged on one end by rubbing with wool. One charged strip is then mounted on an evaporating dish and the other charged strip is used to make the dish spin. Continue reading
41800307 – main blood cells in scale isolated on white background
Cells require a constant supply of glucose and oxygen to produce energy. Cellular respiration occurs in the mitochondria of a cell. As a result of this process, large quantities of waste carbon dioxide must be expelled from the cell. All materials involved in this reaction are either imported or exported through the cell membrane by diffusion.
Students observe the effect of cell volume and surface area on the extent of diffusion of the sodium hydroxide solution through the “cell”.