Tuesday, December 13, 2011

Science for Kids - Ice on a String – Pick Ice cube using thread experiment

If I tell you to pick up an Ice cube using thread what would be your reaction? Of course the condition is, you should not tie a knot to Ice cube using thread. I know some of you must be started thinking me as fool.
Ok, before thinking hard, let’s try the experiment. So our today’s Science project with Ice will require following things – One Ice cube, one thread about 1 feet length, Salt, small cup of water.
Things mentioned above are easily available. Ok here we go, take a thread and insert it into a cup of water. Let the thread be immersed in water until it becomes completely wet. Then lay the string or thread onto ice cube. Make sure that at least an inch of thread is touching the Ice surface. Now sprinkle salt on thread area which is touching the Ice surface. Wait for at least 30 seconds and then pick the thread. You will be amazed to see that, Ice cube also gets picked up by thread.
How come Ice got picked by thread even if I did not tie Ice to thread?
Science Fact –
Let’s understand the facts. If we mix saline substance to other substance and it gets dissolved in the other substance then melting point of that other substance get reduced.
What is melting point – The melting point of a solid substance is the temperature at which it changes the state from solid to liquid. For example, the temperature at which Ice turns into water again is called as melting point of Ice. The normal melting point of Ice is 0 degrees or 0degrees is the temperature at which Ice turns back to water.
Salt (or scientific name – NaCl – Sodium Chloride) is saline substance. When we sprinkle salt on Ice then melting point of Ice is reduced. Means Ice will not turn to water at 0 degrees rather below the 0 degrees temperature. Hence melting point of Ice is reduced because of salt.
When you lay wet string on Ice and sprinkled salt, Ice cube started melting at temperature much below than 0 degrees.  That is temperature of Ice cube surface which is in contact with salt dropped and turned into water.  When the temperature of water regains its original temperature, melted water freezes back to Ice. Thread becomes the part of Ice and Ice cube lifts up easily.
If we mix saline liquid with other substances, then melting point reduced because mixed saline resists crystallization of other substance. More the salinated liquid, more reduction in the melting point. Pure solid state substance will always have high melting point as compared to impure solid state substances.
If you live in a place that has lot of snow, this is the reason why salt is sprinkled on snow during winter on roads by highway departments. This reduces melting point of snow and roads become free of snow and traffic can continue.

If you use Ice and salt in correct ratio then you can lower temperature to -23 degree Celsius. This mixture is widely used in many industries and of course to prepare everyone’s favorite – IceCream.
Hope above experiment was good learning experience for you and you did not get bored.

Stay tuned for more in coming days…

Happy Salting!!!

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