Gasoline is an extremely volatile liquid with a very low flash point. It’s stored in gas stations and other facilities as a safer alternative to storing it as a flammable vapor. Gasoline has a specific gravity of 0.7, which means that it’s not weightless, but it’s also not nearly as heavy as water or other common liquids like motor oil or ethanol. Whether gasoline floats on water or sinks depends on the specific gravity of both liquids. The specific gravity of any liquid measures how dense that liquid is compared to another standard volume of water. Liquids with higher specific gravities are denser than those with lower ones, so if you were to measure the density of gasoline and water at the same temperature and pressure, gasoline would always be heavier than water. Let’s take a closer look at whether gasoline floats or sinks and why that is the case.
Is Gasoline Heavier Than Water?
The short answer is that, no, gasoline is not heavier than water. The specific gravity of gasoline is 0.7 while the specific gravity of water is 1. The specific gravity of a substance is defined as the ratio of the density of the substance to the density of water. Therefore, the specific gravity of gasoline is less than that of water, meaning that it is lighter than water.
Why Gasoline Isn’t Heavier Than Water?
1. Density Is Measured By Mass, Not Volume
The density of a substance is the mass per unit volume of that substance. If you measure the amount of H20 versus the amount of gasoline required to fill a certain volume, you’ll see that gasoline is actually less dense than water. However, in a liquid, molecules are free to move around to some extent. This means that the volume of a liquid varies depending on the temperature and pressure applied. Although it’s a bit of a simplification, you can think of density as the amount of “stuff” in a given volume. The density of water is about 1000 kg/m^3 at standard conditions, whereas the density of gasoline is about 690 kg/m^3. In other words, water has a density that is about 10% greater than gasoline, which is why gasoline floats on top of the water.
2. Gasoline Is More Molar Than Water
Molar mass (or molar weight) is the mass of a substance expressed in grams per mole (which is the number of molecules in a substance). Gasoline is primarily composed of long hydrocarbon chains, with a molecular mass of around 80-95 g/mol. In comparison, water (H20) has a molecular mass of 18 g/mol. This means that gasoline molecules are much heavier than water molecules. However, it’s important to note that molar mass is a very limited way to determine density. The density of a liquid is primarily determined by the number of dissolved molecules: if you have more molecules in a given volume, the density of the liquid will be greater. Since water molecules are smaller than gasoline molecules, there are more of them in a given volume. This means that the overall density of gasoline (including the ethanol added as an antifreeze) is actually less than water.
3. Air Has A Greater Density Than Gasoline
The air inside a gas tank is mostly made up of nitrogen and oxygen (79% and 21% respectively). Since oxygen is heavier than nitrogen, the air inside a fuel tank has a higher density than gasoline. As a result, the air settles at the bottom of the tank while the gasoline sits on top. This is one reason why some vehicles require you to fill the tank while the engine is off; the gasoline may start to flow if the tank is pressurized.
4. Water Has A Greater Density Than Oil
There are many different compounds in crude oil, with varying molecular masses. However, the most abundant compound is methane (CH4), with a molecular mass of 16 g/mol. In comparison, water has a molecular mass of 18 g/mol. This means that water has a greater density than crude oil. Crude oil is often found near the surface of ponds and lakes because it’s less dense than the water around it. This is also why crude is often transported via pipelines under the ocean.
Why Does Gasoline Sink?
- Gasoline has a lower specific gravity than water, which means that it’s less dense than water. This means that gasoline will naturally rise to the top of any nearby water source, meaning that it will naturally float on the surface of the water. However, gasoline also has another feature that causes it to sink. In fact, gasoline is a mixture of several different hydrocarbons, and one of these is toxic benzene, which is heavier than water. This means that even though gasoline has a lower specific gravity than water, it also contains a heavier substance that causes it to sink. Now, in order to mix the two substances, you could pour the water into the gasoline. In most cases, you’d notice that the gasoline mixes with the water.
- Gasoline is a mixture of chemicals. Because it’s less dense than water, it will float in water. However, if you take a sample of gasoline and add it to water and let them sit together, the gasoline will sink to the bottom of the container. The reason for this is that gasoline consists of hydrocarbons. These are molecules that are composed of hydrogen and carbon atoms arranged in chains. In order for these chains to remain in their liquid phase, they must be surrounded by other hydrocarbon chains with less energy than they have.
- When gasoline mixes with water, it forms an emulsion that has the same weight as the original volume of gasoline did before mixing with water (it is 7 times heavier than freshwater). If you separate the two layers through settling or decanting, you can recover your original volume of fuel. The reason why oil floats on top of the water is that oil molecules are lighter than those found in freshwater (freshwater consists).
When Does Gasoline Float On Water?
- If the temperature of the water is lower than the temperature of the gasoline, the gasoline will be lighter than the water.
- This phenomenon can occur if you spill gasoline in water or if there’s a leak. As the gasoline floats to the top of the water, it displaces the less-volatile water below it, creating a hazard.
- If the temperature of the water and gasoline are the same, there is no difference in density between the two. This means that the liquid has no reason to “float” on top of the water.
What Happens When You Mix Gasoline And Water?
- Let’s say you mix a large sample of water and gasoline. In this case, depending on the proportions of each substance, you may notice that the fuel floats on the surface of the water or sinks to the bottom of it. Well, if you have more gasoline than water, then due to its lower specific gravity, it will naturally rise to the top of the mixture since it displaces less water than the water does.
- However, if you have more water than gasoline, then gasoline will tend to sink to the bottom. In fact, gasoline is so dense that if you have more than nine times more water than it, it will sink to the bottom of the water, no matter if you pour the water into the gasoline or vice versa.
- Combining gasoline and water can be dangerous because it creates a mixture that is explosive. The mixture of the two liquids forms a chemical called methyl alcohol, which is highly flammable. If the mixture is heated, it can ignite and create a fire or explosion.
- Gasoline floats on water because its specific gravity is less than one. In other words, it’s lighter than water. While gasoline floats on water, other liquids with lower densities (specific gravities) will also float on top of the water.
- Concentration refers to the amount of matter in a given volume of a substance at a specific temperature and pressure. It is expressed in moles per liter or moles per cubic meter (mol/L or mol/m3). A mole (mol) is equal to 6.022 x 1023 particles and molecules; 1 mole of any substance contains Avogadro’s
Final Words
The specific gravity of any liquid is determined by measuring how dense that liquid is compared to another standard volume of water. Gasoline has a specific gravity of 0.7, which means that it’s not weightless, but it’s also not nearly as heavy as water or other common liquids like motor oil or ethanol. If you were to pour a sample of gasoline into a glass of water, you’d notice that the gasoline doesn’t mix with the water. In Depending on the proportions of each substance, you may notice that the fuel floats on the surface of the water or sinks to the bottom of it.
