Lead is the world’s most famous example of a material that lacks buoyancy. An object made of lead will sink like an anchor, whether shaped into a ball or a boat, no matter how big or small it is. This same property also makes using lead in large quantities very hazardous to human health because its heavyweight causes people to inhale so much more of it than they would otherwise.
Why Does Lead Not Float in Water?
Anything that is significantly less dense than water will float on water. Lead sinks because it has almost 11 times the density of water, which is typically defined as 1 gram/cubic centimeter, or 1 g/cm3.
Lead doesn’t float because it has greater specific gravity than 11.3466, which means that each cubic centimeter of lead (1 g/cm^3) will displace more than 1 cubic centimeter of water (1 g/cm^3). In simpler words, approximately 11 grams of water will be replaced by 1 gram of lead. So when you put something made of lead in water, that cc of lead is pressing down on the 1 cc of water below it with force greater than its weight and will thus fail to float.
A cubic foot of lead weighs about 544 pounds, which means that even if you were holding it at rest in the air, there is no pressure from below on it. The sole pressure exerted on it would be coming from the atmosphere i.e., the atmospheric pressure.
Of course, you also have to consider the pressure from the air above the liquid surface when it is immersed in water. But let’s ignore that for now because, at sea level, where most people live, air pressure is almost always constant.
How to Make Lead Float in Water?
Apart from having odds, such as specific gravity, all standing against lead, we can still work out things to keep it up and going when brought into contact with water. Yup, there are ways materials as stubborn as lean can be made to float in water. If you understand the concept of buoyancy and specific gravity we explained earlier, you can probably think of 10 ways to do that yourself. However, here are a few:
Saltwater:
The easiest way to make lead float is to add salt to water then add your lead. When you add salt (NaCl) to water, it dissociates into Na+ and Cl– ions. Your piece of lead will sink at first, then start floating on the top. The sodium and chloride ions from table salt are pushed together by electrical interactions. Chloride is larger than sodium which causes them to form a shell around each ion with the smaller ion inside. But this shell is pretty hostile with no room for the lead, which eventually pushes the material upwards.
A Touch of Chemistry:
Water sticks together because of hydrogen bonds. That allows small insects like bugs and butterflies to float on the surface without sinking into the liquid. The lead can be made to float by working around this principle with a tad bit of the magic touch of chemistry.
A few chemicals will be needed.
- A large container of water.
- Hydrogen peroxide (It is available at any drug store).
- Baking soda (sodium bicarbonate).
- A glass beaker or similar type of receptacle.
- Two spoons for stirring and mixing the ingredients experiment is quite simple and easy to do.
First, add 1 spoonful of baking soda into the glass beaker. After that, add 1 spoonful of hydrogen peroxide to the powder and begin to stir it. It will start fizzing. The combination produces a lot of carbon dioxide gas, which is heavier than air and therefore pushes down on the water surface inside the glass beaker.
Although lead is denser than water and sinks, when it contacts this carbon dioxide gas-rich mixture, the gas bubbles attach to its surface and thereby reduce the density of the metal enough so that it can float.
Melting the Lead:
This method can be used with various malleable substances that don’t float on water. What you need to do is melt your lead and pour it on aluminium foil. The melting point of lead is 327 degrees C, whereas Aluminum melts at 567 degrees C, so don’t worry about your foil melting.
Try to spread the lead as much as possible, and since it is malleable, it means its atoms can be rearranged into thin foil. Once you have thinned it down enough, carefully place it into the water. If it is actually thin enough, it will float.
Few Other Methods:
Here are a few other methods you can use to make lead float on water:
- A hollow ball made of very thin sheet of lead will float on the water since it is filled with air. Air, being lighter than water, will displace water to move water. However, this only works if the sheet is thin so that the buoyancy of the water will be enough to lift the ball (This is also what happens in ships, as they are mostly filled with air too).
- You can try covering your piece of lead in tire sap or some viscous oil. In most of the tires, the viscosity of the oil is lower than that of water which will make lead float along with itself. However, this tool is applicable for pieces having larger surface area only.
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