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One of the most significant things that separate Earth from the other planets in our solar system is water. Without water, there is no life, including humans! Water also takes up a vast majority of the Earth’s surface, 70% to be exact.
Most of that 70% isn’t the fresh, drinkable water that we are most familiar with. It’s actually saltwater! Saltwater, the type of water found in seas, oceans, and some lakes, is the most abundant type of water on Earth. But did you know that it isn’t just the saltiness of saltwater that sets it apart, it’s also the weight?
How much does a gallon of saltwater weigh?
A single gallon of saltwater weighs, on average, 8.55 pounds (3.87 kg), but this weight can vary depending on the salinity of the water, the amount of other minerals present, and where the saltwater is from.
Saltwater, surprisingly, isn’t as simple as it seems, and if you need to transport this water or plan on using it for a fish tank, you’re going to want to know exact weights. Read on to find out why not all saltwater weighs the same and if saltwater is heavier than fresh water.
How Much Does a Gallon of Saltwater Weigh?
An average gallon of saltwater weighs 8.55 pounds or 3.87 kilograms, but there are some variations between different types of salt waters.
The average weight of saltwater is based on the weight of salt water that comes from the ocean. Ocean water is the most abundant type of saltwater by far. In fact, saltwater from other bodies of water is incredibly rare by comparison.
The more salt in the water, the heavier it will be. The amount of water dissolved in salt is known as salinity.
The average salinity of ocean water is 3.5%, making it heavier than freshwater, but are there types of saltwater heavier than ocean saltwater? Yes! Different lakes, seas, and lagoons across the world have saltier, and therefore heavier, water than the ocean.
What Are The Heaviest Types of Saltwater?
The heaviest types of saltwater on Earth come from lakes and seas instead of oceans. Five of the saltiest lakes or seas on Earth are:
- Great Salt Lake- 5%-27%
- The Dead Sea- 33.7%
- Garabogazköl- 35%
- Don Juan Pond- 44%
These bodies of water are pretty incredible! The Dead Sea is so salty that the only life that can survive in its waters are microorganisms and a few types of algae, and Don Juan Pond, the saltiest body of water in the world, never freezes even though it is located in Antarctica!
Is Saltwater Heavier or Lighter Than Freshwater?
Saltwater is denser and therefore heavier than freshwater. Freshwater is lighter than salt water.
Simply put, because of the addition of salt to saltwater, it weighs more than fresh water. Salt, or sodium chloride, itself has weight, which means when it’s added to water, it makes the water heavier.
- A gallon of saltwater weighs 8.55 pounds on average.
- A gallon of fresh water weighs 8.34 pounds on average.
How Much Heavier Is Saltwater Than Freshwater?
Since saltwater weighs 8.55 pounds per gallon and freshwater weighs 8.34 pounds per gallon, saltwater weighs 0.21 pounds, or 3.36 ounces, more than freshwater.
A gallon of saltwater and a gallon of freshwater are less than a single pound apart in weight, which might not seem like much, but even that miniscule amount can become problematic when multiplied.
For example, if you are filling a fish tank full of 100 gallons of freshwater, those 100 gallons will weigh 834 pounds total. On the other hand, 100 pounds of saltwater weighs 855 pounds, a whopping 21 pounds difference!
Does Saltwater Weigh More When Frozen?
No, saltwater does not weigh more when frozen, but saltwater does weigh more than ice by volume. So a gallon of seawater that was then frozen will weigh 8.55 pounds, but a gallon of ice would only weigh 7.59 pounds.
When water, whether it be fresh or saltwater, is frozen, it does not change the chemical composition of the water. All the same molecules and atoms that made up the water in the first place will still be present, just moving slower, therefore changing the liquid water into solid ice.
So even though the water will change from its original liquid state to a solid state, it will not weigh any differently.
Does Saltwater For An Aquarium Weigh The Same As Regular Salt Water?
Knowing how much water for an aquarium weighs is important for a multitude of reasons, but the most pressing matter tends to be whether the stand for the aforementioned aquarium can support it when filled with water.
If any calculations are off, even by a little bit, disaster can occur when a tank stand or the tank itself gives out, flooding your home and causing death to any of the tank’s inhabitants.
Because of how catastrophic a miscalculation can be, aquarium owners round up the weight of saltwater, just to be safe.
Yes, saltwater for an aquarium weighs the same as regular saltwater, but to have a decent margin of error, aquarium owners tend to calculate a gallon of aquarium saltwater as 10 pounds per gallon instead of 8.55 pounds per gallon.
It might seem to be going overboard to add almost a pound and a half to each gallon when measuring tank water, but tanks can vary slightly in size and can also be accidentally overfilled.
For these reasons, and to give aquarium owners a little wiggle room safety-wise, measuring a gallon of saltwater for a tank as 10 pounds is the recommended calculation.
What is the weight of saltwater per cubic foot?
Saltwater weighs around 64 pounds per cubic foot.
What does 1 cubic mile of seawater weigh?
One cubic mile of seawater would weigh an incredible 9.2 trillion pounds.
Does saltwater freeze?
Yes, saltwater freezes just like freshwater, but at a lower temperature. Saltwater freezes at roughly 28.4 degrees Fahrenheit, while freshwater freezes at 32 degrees Fahrenheit.