Playing a video (Stop)
Powered by Haskell (GHC 8.8.4 )

https://youtu.be/McttXAsFDNg

Water Bender

Scientific Principle: Static Electricity - Electric Forces

Tools: sink with running water, balloon filled with air, woolen clothing.

How to work:First turn on the faucet to create a steady, narrow stream of water. Then rub the balloon against woolen clothing for about 10 seconds. Finally hold the balloon near the water stream, making sure it doesn’t touch the water, and observe how the stream bends.

Explanation:

Static electricity is a type of electricity that arises from an imbalance between positive and negative charges within a material. This occurs when electrons (the negatively charged particles within an atom) transfer from one material to another. If the material receiving the electrons is either isolated or not an electrical conductor, it tends to retain the electrons, leading to the accumulation of electric charge.

On the other hand, when there is presence of electric charges within matter, electric forces (a type of non-contact force), exert their influence on objects without any physical contact. Since objects can possess positive, negative, or neutral charges electric forces can either attract or repel the objects, depending on the nature of the charges that the objects possess. The magnitude of the force is determined by both the charge and the distance between the objects involved.

In our experiment, when you rub a balloon with woolen clothing or your hair, it accumulates extra electrons, resulting in a net negative charge on the balloon. Water molecules are polar, meaning they have a slightly positively charged end (the H2 end) and a slightly negatively charged end (the O end). When you bring the negatively charged balloon close to a stream of water, the positive ends of the water molecules are attracted to the balloon, causing the stream to bend toward it.

Greek Team

https://youtube.com/shorts/UAp0wLECfM0

Refraction of light

Tools:

- a glass filled with water

- a straw

- drawn arrow

- sphere glass

 

What to do:

- pour water into a glass and put a straw in it - observe how the light refracts, i.e. how the straw looks from the side, and how it looks from above

- look at the drawn arrow through a glass full of water

- look at the arrows through the glass ball

 

Results:

When the light beam goes from a rarer medium into a denser, light refracts toward the perpendicular line to the medium, and when it goes from a denser to a rarer medium it refracts from the perpendicular line to the medium.

This video also shows some effects:

- The arrow behind the glass of water is horizontally reversed

- arrows behind a sphere glass are both: horizontally and vertically reversed

 

Croatian team / Novska

https://youtube.com/shorts/PlV16rEXCDs

 

Pressure is inversely proportional to the surface area

 

Tools: a few plastic cups, a flat tray, and a student's backpack with books or some other heavy object

 

What to do:

1. Place two plastic cups on the table and cover them with a flat tray. Put a heavy object on a flat tray.

2. Place a few plastic cups on the table and repeat the experiment.

 

Explanation:

When we place an object of some mass on two plastic cups, they will break due to the weight of the load, i.e. the pressure created by that weight.

When we place more plastic cups under the load, increasing the area over which the weight is distributed, glasses remain whole, because we have reduced the pressure.

 

Croatian team / High school Novska

https://youtube.com/shorts/d_WfZqnMV_o?feature=share

Electricity and water

 

This video shows how an electrified plastic stick interacts with water.

 

Tools:

- plastic stick

- wool rubber

- a flow of water

 

What to do:

- rub plastic stick with a wool rubber

- bring the stick close to the flow of water, but do not touch it

 

Result:

- as you bring the electrified stick near the flow of water, it moves closer to the stick, because the stick is negatively charged, and water is neutral, so the positive part of the water molecules are brought closer to the stick, which moves the flow of water toward the stick.

 

Croatian Team / Novska

https://youtube.com/shorts/s4ebY_WOkmU

Static Electricity - Electrification by rubbing

 

This video shows how a person can electrify a balloon and see its electric field.

 

Tools:

- a balloon

- a sweater or a T-shirt

- small pieces of paper or someone's hair

 

What to do:

- rub a balloon with a sweater or a T-shirt

- bring the electrified balloon closer to small pieces of paper or someone's hair

 

Result - small pieces of paper or hair are brought to the electrified balloon

 

Caution - it might not work if there is a lot of humidity

 in the air.

 

Croatian Team / Novska

 

https://youtube.com/shorts/93F-5aeZRl8?si=yyxoqC7_RMg2ofqE

 

Water rising into a glass covering candle

 

Scientific Principle:Gay Lussac’s Law

 

Tools:Candles, Beaker or Large Glass, Shallow Dish or Casserole Dish, Butane Lighter,Water

 

How to work:First fill our shallow dish with two or three centimeters of water. The next step in our experiment is to take your candle and place it in the center of the water and light it with a butane lighter. For the final step take your beaker or a large glass and place it over top of the candle. After a little while of having our beaker over the candle you'll notice the candle flame will get smaller and smaller until it is extinguished. If you watch closely you'll see that the water level underneath our beaker begins to rise as the candle fades away. The water level will continue to rise for a short time after the candle has been fully extinguished. You'll notice that the water underneath the beaker is much higher than the water in the shallow dish.

 

Explanation:Gay Lussac’s Law states that the temperature and pressure of an ideal gas are directly proportional, as long as its mass and volume remain constant. This means that as the temperature increases the pressure increases and vice versa.

 

In our experiment, the beaker contains gaseous air molecules. The energy from the flames is transferred to these air molecules, exciting them and raising their temperature. As the air molecules become more excited, they attempt to spread further apart. However, since the beaker does not expand like a balloon, the volume of space available for the air molecules is limited. Consequently, the air molecules exert increasing pressure against the beaker’s walls and the water at its base.

 

This rise in air pressure within the beaker causes the water level underneath it to be lower than the water level outside. The higher the temperature or energy of the air molecules, the greater the pressure created under the beaker. As the candle flames burn, they consume some of the oxygen in the beaker for combustion. The resulting products are carbon dioxide gas and water vapor. With more hot carbon dioxide gases and water vapor produced, they accumulate at the top of the beaker, displacing the oxygen needed for the candles to burn.

 

Once the flame is extinguished, the air molecules under the beaker cool down, losing their excitement and lowering the temperature. Consequently, the pressure exerted by the air molecules against the beaker’s sides and the water at its base decreases. To achieve equilibrium, the air under the beaker pulls on the sides and the water, causing the water level inside the beaker to rise and equalize the pressure.

 

Greek team

https://www.youtube.com/watch?v=4rGr7UGaxQk

Density column experiment

Scientific principle: Less dense matter floats above denser matter.

Tools: empty test tubes or beakers, materials of different densities (vegetable oil, colored water, dishwashing soap, alcohol, glue, sugar solution)

How to work: We start pouring the materials one by one, but quietly and carefully. It is preferable to pour the materials so that they flow quietly along the wall of the inner tube.

Result: We will notice that the materials are arranged so that the material with the greatest density will remain at the bottom of the tube, then the material with the lowest density will be above it, and thus we get a column of materials arranged according to their density, with the highest density material at the bottom, and the least dense material at the top.

Note: More materials than those used in the experiment may be used.

- Consult your teacher first.

Jordan Team

https://www.youtube.com/watch?v=OdQ-cRoLrWs

Car model industry

Scientific principle: Using Newton's third law (action and reaction)

Tools: an empty soft drink can, wooden sticks (we will use them as car axes), a balloon, adhesive, a tool for piercing the plastic can (an iron nail, for example, + wooden tongs)

How to work: We first heated the iron nail over the flame with the help of the teacher (be careful), then we pierced the plastic can four holes (two holes opposite each other), after that we inserted the wooden sticks into the holes, then using silicone adhesive we installed the covers of the plastic cans as car wheels. After that, we inflated the balloon and attached it to the top of the car using adhesive tape. When all the cars were ready, we held a competition for the car that would travel the greatest distance (https://www.youtube.com/watch?v=zZIGiMDsMzM ). It was a fun experience.

Jordan Team

Physics-experiments