Learn the proper procedures for washing your hands and help prevent the spread of infection.

Negative Pressure Exists! http://bit.ly/TFilQ8
Vsauce's Space Straw: http://bit.ly/XubIm3
Smarter Every Day's Prince Rupert's Drop: http://bit.ly/10VQBGW
ViHart's Optimal Potatoes: http://bit.ly/14egJoe

Thanks to Questacon for filming! Check out their slow-mo playlist: http://bit.ly/ZoWFGR
Science Alert brings science to your news feed: http://on.fb.me/14ehuxA

Music by Kevin Mcleod (http://incompetech.com): Pale Rider & The Cannery

What is the longest drinking straw that you can actually drink out of? Well in this video, we put the theory to the test. We started off with a one metre long straw made out of drinking straws taped together. We moved on to two pieces of plastic tubing, each 6 metres in length with different diameters. Then we tried a 10.5 metre tube over a cliff's edge. The maximum we achieved was about 7 metres though theoretically up to 10.3 metres is possible if a perfect vacuum is created.

Acetylene burns brightly when calcium carbide reacts with ice.

This video is part of the Flinn Scientific Best Practices for Teaching Chemistry Video Series, a collection of over 125 hours of free professional development training for chemistry teachers - http://elearning.flinnsci.com

ATTENTION: This demonstration is intended for and should only be performed by certified science instructors in a safe laboratory/classroom setting.

All purpose flour is spread out over several birthday candles. Since the flour particles are spread out, they have enough oxygen gas molecules to react with and hence the flour burns quickly.

Beautiful reflective coating of silver plates out on the inside of flasks or glass ornaments. Redox reaction "mirrors" the way silver mirrors are actually produced!

This video is part of the Flinn Scientific Best Practices for Teaching Chemistry Video Series, a collection of over 125 hours of free professional development training for chemistry teachers - http://elearning.flinnsci.com

ATTENTION: This demonstration is intended for and should only be performed by certified science instructors in a safe laboratory/classroom setting.

Compare physical and chemical changes using regular paper and flash paper.

This video is part of the Flinn Scientific Best Practices for Teaching Chemistry Video Series, a collection of over 125 hours of free professional development training for chemistry teachers - http://elearning.flinnsci.com

ATTENTION: This demonstration is intended for and should only be performed by certified science instructors in a safe laboratory/classroom setting.

When a grape is cut nearly in half and placed in a microwave, plasma is produced. Please use caution if attempting this experiment: don't leave the microwave on for too long, make sure the area is well ventilated, and stand back. Remember the contents will be very hot afterwards.

http://www.abc.net.au/catalyst/. Oceans are silently choking on our plastic waste. Plastic and synthetic materials are the most common types of debris in our oceans and are having horrific impacts on marine wildlife and systems. As an island continent "girt by sea" marine debris is of particular importance for Australia. Creatures get entangled in plastics and drown and ingested concentrated toxins from plastics pose a threat to the health of the food chain. Plastics also transport and introduce species into new environments. Anja Taylor catches up with the CSIRO research team spearheading the Marine Debris Survey, a world first study of the plastics around our coastline.

When air is compressed very quickly, it can reach high temperatures. In this demonstration we show how cotton wool can reach the point of auto-ignition by quick compression of air in the fire syringe.

Synthesis reaction releases light and heat.

This video is part of the Flinn Scientific Best Practices for Teaching Chemistry Video Series, a collection of over 125 hours of free professional development training for chemistry teachers - http://elearning.flinnsci.com

ATTENTION: This demonstration is intended for and should only be performed by certified science instructors in a safe laboratory/classroom setting.

Shoot a Nerf ball from PVC pipe using the energy released when alcohol burns.

This video is part of the Flinn Scientific Best Practices for Teaching Chemistry Video Series, a collection of over 125 hours of free professional development training for chemistry teachers - http://elearning.flinnsci.com

ATTENTION: This demonstration is intended for and should only be performed by certified science instructors in a safe laboratory/classroom setting.

Exciting, popular demonstration illustrates the fire triangle.

This video is part of the Flinn Scientific Best Practices for Teaching Chemistry Video Series, a collection of over 125 hours of free professional development training for chemistry teachers - http://elearning.flinnsci.com

ATTENTION: This demonstration is intended for and should only be performed by certified science instructors in a safe laboratory/classroom setting.

Dramatic demonstration of the effect of particle size and surface area on the rate of combustion.

This video is part of the Flinn Scientific Best Practices for Teaching Chemistry Video Series, a collection of over 125 hours of free professional development training for chemistry teachers - http://elearning.flinnsci.com

ATTENTION: This demonstration is intended for and should only be performed by certified science instructors in a safe laboratory/classroom setting.

Einstein's classic thought experiment involves sitting on a train travelling at the speed of light. If you hold a mirror in front of your face, will you see your reflection in a mirror? How could light from your face reach the mirror if the mirror is travelling away from you? But it would be a pretty spooky train if you couldn't see your reflection so Einstein felt this solution wasn't realistic. On the other hand if you could see your reflection, it would mean light was travelling at the speed of light inside the train. But that meant the same light observed from outside the train would be going twice the speed of light. This again seems inconsistent. So Einstein resolved that you must see your reflection but that light must travel at the same speed inside and outside the train. The only way this is possible is if space and time are perceived differently by observers inside and outside the train.

An introduction to alpha, beta, and gamma radiation

Microwave grape plasma: http://www.youtube.com/watch?v=RwTjsRt0Fzo
Northern Lights: http://www.youtube.com/watch?v=knwiWm4DpvQ
Nanodiamonds in candle flames: http://www.youtube.com/watch?v=KzOkuGQC3Rw
Relight Candle Trick: http://www.youtube.com/watch?v=1tXPVTIisl0

Is a flame really a plasma? Well it depends on your definition of plasma, but there are certainly ions in a flame, formed as molecules collide with each other at high speed, sometimes knocking electrons off of their atoms.

Special thanks to the Palais de la Decouverte for helping me perform this experiment. Using tens of thousands of volts on two metal plates, we created a strong electric field around the plasma. This pulled positive ions in one direction and negative ions in the other direction elongating the flame horizontally and causing it to flicker like a "papillon" (butterfly). Then we showed that much longer sparks can be made through the flame than through air since the ions increase the conductivity.

Light is so common that we rarely think about what it really is. But just over two hundred years ago, a groundbreaking experiment answered the question that had occupied physicists for centuries. Is light made up of waves or particles?

The experiment was conducted by Thomas Young and is known as Young's Double Slit Experiment. This famous experiment is actually a simplification of a series of experiments on light conducted by Young. In a completely darkened room, Young allowed a thin beam of sunlight to pass through an aperture on his window and onto two narrow, closely spaced openings (the double slit). This sunlight then cast a shadow onto the wall behind the apparatus. Young found that the light diffracted as it passed through the slits, and then interfered with itself, created a series of light and dark spots. Since the sunlight consists of all colours of the rainbow, these colours were also visible in the projected spots. Young concluded that light consist of waves and not particles since only waves were known to diffract and interfere in exactly the manner that light did in his experiment.

The way I have always seen this experiment performed is with a laser and a manufactured double slit but since the experiment was conducted in 1801 I have always thought that it should be possible to recreate the experiment using sunlight and household materials. That is basically what I did here. I will show the interference pattern I observed with my homemade double slit on 2Veritasium but I chose to use a manufactured double slit here to ensure that the pattern was impressive for observers at the beach.

Special thanks to Henry, Brady, and Rupert for their cameos, Glen for filming and Josh for helping create the apparatus. Thanks also to the Royal Society for allowing us to view the original manuscript of Young's lecture and the University of Sydney for lending the double slits.

Music by Kevin Mcleod (incompetech.com) Danse Macabre, Scissors

A 16mm film now incorporated into my article http://www.gcmstudio.com/acoustics/acoustics.html because it's not only relevant to water, but sound and light waves as well. It is from my own collection that clearly demonstrates how 2 sources of vibration interact. Anybody who uses more that 1 speaker to listen to audio should see this, especially engineers. It shows an ideal world, free of reflections (echoes or reverberation) but is educational never the less.
Yet, this form of interference is largely ignored, even in texts about acoustics.

It has been edited for time but no concepts covered have been removed.

The world's roundest object helps solve the longest running problem in measurement -- how to define the kilogram.
A kilogram isn't what it used to be. Literally. The original name for it was the 'grave', proposed in 1793 but it fell victim to the French Revolution like its creator, Lavoisier. So begins the tale of the most unusual SI unit. The kilogram is the only base unit with a prefix in its name, and the only one still defined by a physical artifact, the international prototype kilogram or IPK.

But the problem with this definition has long been apparent. The IPK doesn't seem to maintain its mass compared to 40 similar cylinders minted at the same time. The goal is therefore to eliminate the kilogram's dependence on a physical object. Two main approaches are being considered to achieve this end: the Avogadro Project and the Watt Balance.

The Avogadro project aims to redefine Avogadro's constant (currently defined by the kilogram -- the number of atoms in 12 g of carbon-12) and reverse the relationship so that the kilogram is precisely specified by Avogadro's constant. This method required creating the most perfect sphere on Earth. It is made out of a single crystal of silicon 28 atoms. By carefully measuring the diameter, the volume can be precisely specified. Since the atom spacing of silicon is well known, the number of atoms in a sphere can be accurately calculated. This allows for a very precise determination of Avogadro's constant.

Special thanks to Katie Green, Dr. David Farrant, the CSIRO, and the National Measurment Institute for their help. Thanks also to Nessy Hill for filming and reviewing earlier drafts of this video.

There is debate as to whether this is truly the roundest object ever created. The Gravity Probe-B rotors are also spherical with very low tolerances such that they may in fact be rounder.

Music by Kevin McLeod (incompetech.com) Decision, Danse Macabre, Scissors