Observations and resultsDid the egg float in cup 1 and 2, but not in cups 3, 4 or 5? You likely saw that the egg floated best in cup 1, floated a little less in cup 2 (but part of it was above the surface) and did not float in the other cups. Cup 1 had the undiluted salty solution that you originally prepared, which was one half cup of salt in two and one half cups water total. The concentrations of the salt solutions in cups 2 to 4 were halved as you increased in cup number; for example, the concentration of the salt in cup 2 was half that of cup 1, and the concentration of the salt in cup 3 was half again of cup 2. (Cup 5 had plain tap water.) The egg should have sunk in cups 3, 4 and 5 because the density of the egg was higher than the density of the solutions (or plain tap water) in those cups. Cups 1 and 2 had more salt in them than the other cups (with cup 1 having the most salt), which means these solutions were denser. The egg should have floated (with part of it above the water surface) in these two cups because the solutions were denser than the egg. The actual density of the egg is in between the density of the solution in cup 3 and that in cup 2. More to exploreWhat Is Density?, from Charles E. Ophardt, Elmhurst CollegeWhy Is the Ocean Salty?, from Herbert Swenson, U.S. Geological Survey PublicationFun, Science Activities for You and Your Family, from Science BuddiesHow Salty Does the Sea Have to Be for an Egg to Float?, from Science Buddies
Just as air can have different densities, water can have different densities as well. As the salinity of water increases, the density increases as well. Fresh eggs will float saltwater, but will sink in freshwater. This will show that as the salinity increases the density also increases.
Why Does Adding Salt To Water Make An Egg Float EXCLUSIVE
The increased density of salty water increases the weight of water. An egg will be buoyant (float) if the weight of the egg is less than the weight of the water it displaces. The egg sinks if it weighs more than the weight of the water that is displaced.
Have you ever wondered why some objects float on top of the ocean, and other objects sink to the bottom? It has to do with the density of the objects compared to the density of the salt water surrounding them in the ocean. If you add salt to plain water, it increases the density of the water. In fact, if you add enough salt, you can make the water so dense that an egg will actually float in it! Explore how this works in this science activity.
If you put an egg in a cup of tap water, it will sink to the bottom. But, if you add enough salt, the egg will float back up to the surface! Why is this? Because the density of the egg is higher than the density of tap water, the egg sinks. Density is the mass of a material per unit volume. For example, the density of freshwater under standard conditions is approximately one gram per cubic centimeter. Adding salt to the water increases the density of the water because the salt increases the mass without changing the volume very much.
Extra: In this science activity you figured out, within a factor of two, how much salt it takes to float an egg. You could narrow down the range further by testing additional salt water dilutions to try and determine the density of the egg. To do this, start your dilution with the salt concentration in which the egg first floated and make a new dilution series, as you did before. Now in which cup does the egg first float? What does this tell you about the density of the egg?
You likely saw that the egg floated best in cup one, floated a little less in cup two (but still had part of the egg above the water level), and did not float in the other cups. Cup one had the undiluted salty solution that you originally prepared, which was cup salt in 2 cups water total. The concentrations of the salt solutions in cups two to four were halved as you increased in cup number; for example, the concentration of the salt in cup two was half that of cup one, and the concentration of the salt in cup three was half that of cup two. (Cup five had plain tap water.) The egg should have sank in cups three, four and five because the density of the egg was higher than the density of the solutions (or plain tap water) in those cups. Cups one and two had more salt in them than the other cups (with cup one having the most salt), which means these solutions were denser. The egg should have floated (with part of it above the water level) in these two cups because the solutions were denser than the egg. The actual density of the egg is in between the density of the solution in cup three and the solution in cup two.
Fill two clear glasses with lukewarm water. Pour 1 tablespoon of salt into one glass, and stir until the salt dissolves. Gently drop a fresh egg into the plain water. The egg will sink to the bottom. Remove the egg and place it in the saltwater. The egg will float.
The higher the salt content of water, the higher an object will float. If you add less than 1 tablespoon of salt to a glass of water, it is possible to make the egg float in the middle. This also can be accomplished by adding 1 tablespoon of salt to water and not stirring. Because the salt is denser than the water, the salt will sink. When you drop the egg into the water, it will sink through the plain water until it reaches the saltwater at the bottom of the glass. The density of the saltwater prevents the egg from sinking any lower, so the egg will float in the middle of the glass.
Try this experiment again, but instead of using an egg use a potato slice or a carrot slice. You will have to play around with the amount of salt you add to the water because all objects have their own unique density. Add salt a tablespoon at a time and mix well until you cannot see any salt in the solution, then add your object to see if it floats or sinks. Remove your object and keep adding salt until you can get your object to float. To make it a true science experiment, create a data table to keep track of how much salt you add to the solution.
The egg floats because the density of the salt water changes to be greater than the egg and the density of the egg becomes less dense so then the egg floats. But when you put an egg in tapwater the density of the egg is greater than the density of the tapwater which makes the egg sink.
The egg is denser than the fresh water (more molecules per square inch), this causes it to sink. When you start dissolving salt in the water, this is increasing the density (adding more molecules per square inch). Eventually the water becomes denser than the egg causing the egg to float. When you carefully add fresh water again, this fresh water is less dense than the salt water so it floats right on top!
In order to make the egg float, we need to makeit less dense than the water surrounding it. Asyour teacher has probably explained in class,adding salt makes the surrounding solution moredense. How much salt we need to add will vary fromegg to egg, since the density of each egg willprobably be slightly different. However, we canmake a rough estimation! According to a couple ofwebsites I found online, eggs have a density ofabout 1.03g/mL. That means in a volume of 1mL,there is about 1.03g of the stuff that comprisesan egg. The density of pure water is about1.00g/mL. So let's calculate how much salt we needto add to account for this difference indensities!
To make the calculation a little easier, let usassume we have 1L of water. We need to figure outhow many grams of salt to add to the water toincrease the density by at least 0.03g/mL. Theequation we want to solve for this problem is:
Now, it is important to keep in mind that thedensity of the egg varies and you may not use 1Lof water, but some other amount. This means theamount of salt we would need to add will vary aswell, but this is a ball-park estimate of abouthow much salt we should add (i.e. we would beadding tablespoons as opposed to cups of salt to1L of water). I hope this helps!
The reason the egg can float in saltwater is thatsaltwater has a higher density than freshwater.The density increases with salt concentration, sothe amount of salt you need might depend slightlyon the egg. A good starting point would be 6tablespoons of salt in 1 glass of water (make sureit is fully dissolved by stirring). If the eggdoes not float, just add some more salt!
You want to know how much salt it would take tohave an egg float in water. An object, such as anegg or a boat, can float in water if it candisplace enough water to match its own mass. Thereare 2 general ways to do displace water. One, you can design the object to displace a lotof water, such as boats. Two, you can make eitherthe object less dense than the water. In the caseof eggs, the second option is more appropriatesince it is difficult to reshape an egg into aboat.
Salt adds mass while adding very little volumeso it is a good additive to make the densityhigher. Adding salt increases the mass but volumestays constant. The density will increase with theamount of salt you are adding.
The explanation behind this phenomenon is simple - DENSITY! In the Salt Water Egg experiment, you have observed that the egg placed in saltwater floated and the one in tap water didn't. Because saltwater is denser than fresh water, the egg does not end up sinking like it usually does!
Now let's go back to the question of why objects float or sink. Placing an object that's denser than fresh water automatically sinks. In our Salt Water Egg experiment, because the egg is denser than tap water, it pushes away water particles so it can make space for itself hence the sinking motion. But in the case of the salt water, since it is heavier than ordinary tap water, it is more capable of holding the egg up - hence the egg floating. In easier words, objects sink when their own density is greater than the liquid's density.
Now you must be wondering what's in the salt that makes water denser when mixed with it? When salt is added and dissolved in water, it breaks down into ions that are then attracted to the water molecules. This attraction causes them to bind tightly, increasing the amount of matter per volume (density). Instead of just having the molecules hydrogen and oxygen in the water, sodium and chlorine joins the equation (since salt is made up of sodium and chlorine particles). Saltwater now has more particles in it compared to the ordinary tap water we started with. This is why saltwater is denser than tap water. 2ff7e9595c
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