Tuesday, 28 October 2014

Air 'Bergas' + Gula-gula 'Berpudina' = Air Pancut

Apa yang diperlukan?
Bahan-bahan yang diperlukan untuk menjalankan eksperimen ini adalah sebotol minuman ringan bergas (sebarang perisa) dan beberapa biji gula-gula berpudina. 

Bagaimana cara membuatnya?
Buatkan satu lubang kecil pada penutup botol. Ikatkan gula-gula berpudina pada seutas benang. Kemudian, masukkan benang tersebut melalui lubang pada penutup botol dan biarkan gula-gula berpudina di bahagian bawah penutup botol (sila rujuk pada gambarajah  di bawah). Tuang keluar sedikit air bergas dari botol tersebut (anggaran sehingga paras di mana gula-gula berpudina tidak akan mencecah air bergas di dalam botol). Kemudian, tutup dengan kemas penutup botol tersebut. Pegang tali dengan kemas. Akhir sekali, lepaskan tali tersebut. Gula-gula berpudina akan masuk ke dalam minuman bergas. Perhatikan apa yang berlaku. Air pancut akan terhasil melalui lubang pada penutup botol. 

1. Penyediaan untuk eksperimen ini perlu dijalankan dengan kadar yang segera bagi mendapatkan kesan yang lebih ketara.
2. Untuk melakukan eksperimen ini, gula-gula tersebut boleh juga dimasukkan begitu sahaja ke dalam botol minuman bergas (tidak semestinya diikat pada tali) tetapi cara yang dinyatakan di atas  adalah untuk mendapatkan kesan yang lebih ketara.

Apa yang berlaku?
Di dalam air bergas terdapat gas karbon dioksida. Gas ini sebenarnya yang menyebabkan rasa 'gas' di dalam minuman ringan. Apabila gula-gula dimasukan ke dalam air bergas, sejenis bahan kimia yang terdapat dalam gula-gula berpudina tersebut iaitu 'Arabic Gum' akan melemahkan ketegangan permukaan air bergas dan menyebakan gas karbon dioksida di dalam minuman akan mengembang. Proses ini dibantu juga dengan dengan permukaan gula-gula berpudina  yang kasar yang menyebabkan lebih banyak lagi gas karbon dioksida yang akan terhasil. Proses ini dinamakan 'penukleusan'. Oleh kerana telalu banyak gas karbon dioksida yang terhasil, maka tekanan di dalam botol menjadi tinggi dan seterusnya menyebabkan letusan air pancut keluar dari lubang pada penutup botol tersebut. 

Posted by Ayu
Learning Specialist, Petrosains

Tuesday, 21 October 2014

Can You Hold Fire In Your Hand?

Fire is very dangerous. But, did you know that you actually can juggle it in your hands with a bit of help from science? To do so, you need to make a cloth ball that's made of 100% cotton. You could use your old t-shirts to make itTake the piece of cloth, then roll it up into a ball. Push the thread through the cloth with a needle. Wrap and sew it into a shape of ballMake sure it is not synthetic fibre like nylon or polyester because it might burn or melt, with unpleasant consequences. Other materials that you will need to prepare are some hand sanitizer, salt, a lighter, a fire-proof baking or frying pan, tongs and a responsible adult to help you.
To start with, you will need to locate and prepare a safe environment. While these handheld fireballs maintain low temperatures, it can still burn and ignite other materials in the process. Put a pail of water nearby or do it near a sink. In case you panic you can just drop the fireball into the pail or sink. You can also put the frying pan lid over the fireball to suffocate the flame. There is no point in trying to blow the fireball out as it is quite hard to do so. 

First, mix the hand sanitizer with some salt and swirl it in the baking pan. Soak the cloth ball in that mixture with tongs. To further protect your hands, sprinkle some water on your palm to create a barrier from the heat. Use tongs to pick the cloth ball up. Get your responsible adult to light it and then quickly roll the ball back and forth with both hands so that you won’t feel the heat or burn your hands. The trick is to not hold it for too long in one hand. Put it back in the baking pan when you lose your courage handling it.  Ta-da!

Salt is added to the hand sanitizer to give off yellow flames so that you can see it. If salt is not added, the flame will be almost invisible or blue and white in color. It doesn’t hurt when you hold the fireball because ethanol from the hand sanitizer evaporates before the ball gets hot. Another reason is because the heat is not being transferred to the hands as the ball is moving constantly. Here's a video of how we do it in Petrosains:

The process of combustion requires 3 main properties which are oxygen, fuel and heat. In this case, fuel comes from the ethanol in the hand sanitizer and the heat is from the lighter.

The fireballs are reusable. Put them out when they run out of fuel or else the cotton will burn (you can tell this is happening when the ball starts to blacken and produce sooty smoke). If you get to the point where the cotton itself is burning, the fireball will be too hot to hold. Ideally you should extinguish the fireball before it consumes all of its fuel. To reuse it, soak it in more lighter fluid and relight it. 

Lastly, remember to use proper safety precautions and common sense. Don't get burned or set your house on fire. This project is best for adults. If you're not an adult, make sure you have FULL ADULT SUPERVISION and assistance! Stay safe, enjoy and understand the science.

Shared by Melissa
Guest Blogger

Saturday, 11 October 2014

Do Fish Urinate?

Yes they do!  But why?

Well, like most living things, fish too produce waste from their metabolic processes.   Peeing is one way of doing that and is referred to as excretion.  Elimination on the other hand refers to pooping, i.e. the removal of solid waste comprising undigested foods and digestive by-products.  How much they pee depends on the environment they live in and the adaptations it has undergone for survival.

Marine fish drink a lot while freshwater fish pee a lot. Why?

Freshwater Fish and Marine Fish
The difference between these two types of fish lies in the salinity of the fish’s environment and the inside of its body. Since the fish’s skin is so thin, especially around places like the gills, external water constantly tries to invade the fish’s body by osmosis and diffusion.

Image credit: Indiana University-Purdue University Indianapolis Earth Sciences

Maintaining the Balance
Osmosis takes place when two solutions are separated by a partially permeable membrane. A partially permeable membrane lets some particles through but not others. Cell membranes are partially permeable. Water can move freely through them but other particles, such as sugar molecules, cannot.

Osmoregulation is the process of maintaining an internal balance of salt and water in a fish’s body and is carried out with the help of the kidneys.  Do bear in mind that a fish is a collection of fluids floating in a fluid environment, with only a thin skin to separate the two.  

Role of the Kidneys
The kidneys are slightly different from mammals. They are smaller, stretched and do not resemble beans. Generally, within fish, the kidney is located towards the very middle of the fish both lengthwise and height wise.

Freshwater Fish
Body is more saline than the surrounding water and constantly gains water from the environment

The kidney prevents excess solute loss as they contain more salts within their blood than the water located around their bodies. 

Water will diffuse into the fish through osmosis causing large amounts of water to build up inside. 
The kidney will then increase the amount of water that passes out in the urine and actively reabsorb the salts that would pass out to maintain balance. 
This results in the production and excretion of large amounts of dilute urine - almost completely composed of water.

Marine Fish
Body is less saline than the surrounding water and constantly loses water to the environment.

The function of the kidney here is almost opposite to that of the freshwater fish as the water and liquid around them is highly concentrated with salts and other solutes. 
Water in the fish is constantly being 'sucked out' into the surrounding water through osmosis. This is because the fluids inside their bodies are less concentrated than the saltwater around their bodies. 
The fish must counteract this process through drinking water and the use of their kidneys. 
By constantly taking in water, the fish is constantly replacing water that is sucked out of it however, this can lead to an extreme intake of salts and buildup of harmful substances within the fish. 
These salts are removed through the use of the kidneys whereby they help the fish retain water and actively excrete salts to produce a very concentrated urine. This also means that marine fish do not urinate as much as freshwater fish.

Shared by Azni
Learning Specialist, Petrosains

Friday, 3 October 2014

Ukulele From A Box?

If you have ever imagined creating a ukulele out of a box, you are at the right page! It's called a 'box-elele'! This box-elele is constructed using a cardboard box and has 4 ukulele strings made of nylon polymer. The size of a box-elele is similar to the figure-eight body shape of a typical ukulele. 

Here's how to make a DIY Box-elele :-

Step 1

Place a small rectangular board (white side up) underneath a long piece of wood. Using a pencil, mark the position for the holes on the board.

Step 2

Punch out 4 holes based on your markings. Repeat these steps with the other board.

Step 3

Place both boards onto the wood, ensuring that the holes are clear. Insert the gears into each hole, secure tightly with 2 small screws using a screwdriver.

Step 4

Place the piece of wood in the inner middle part of the box cover & glue it together. Let it dry!

Step 5

Draw four lines (1 cm apart) across the square board. Using a cutter, poke holes along the lines.

Step 6
Fold the board based on the lines, forming a triangle-shaped saddle. Tape the saddle with masking tape to keep it in shape. Then glue the saddle 9 cm from the middle-end of the box cover. 

Step 7

Measure 3 cm from the end of the saddle and draw a 4 cm line parallel to the saddle. Mark or indent 4 holes (1 cm apart) on the line. 

Step 8

To make the bridge, screw 4 big screws into each hole markings / indents. Leave a 0.5 cm gap between the surface and screw head.

Step 9

To make a second saddle, tape 2 mini boards together. Then, tape a bolt to the boards. After that, glue the second saddle next to the first one. 

Step 10

Glue the long boards one by one onto the neck to make the fretboard.

Step 11

To make the nut, tape 4 small boards together. Then, tape the bolt to the boards. Then, glue the nut on top of the fretboard.

Step 12

Measure the scale length which is the distance from nut to bridge.

Nut to First Fret
(NutToFret[1]) = (Scale Length))/17.817

Round up to three decimal places

Nut to Second Fret

Calculate value of bridge to first fret:
BridgeToFret[1] = ScaleLength – NutToFret[1]

Formula for second fret

NutToFret[2] = (BridgeToFret[1])/17.817  + NutToFret[1]

General Formula for all Frets
First step:
BridgeToFret[n-1] = ScaleLength – NutToFret[n-1]

Second fret (and after):
NutToFret[n] = (BridgeToFret[n−1])/17.817  + NutToFret[n-1]

Step 13

Tie one end of the string to the bridge. Insert the other end of the string through the tuning peg and tighten it by turning the peg head. 

Step 14

Ensure that you have strung your box-elele correctly.

Step 15

You have finished building your box-elele

Try strumming out a song!

Shared by Izhana