The density of water at 4 degrees Celsius is 8.345 lbs/U.S. gal. This is equal to a rounded value of 1 gram per milliliter (g/ml) or 1 gram per cubic centimeter (g/cm3) or 1000 kg/m3.
Water has a maximum density of 39.2ºF or 4ºC.
At this temperature, a gallon of water weighs around 8.345 lbs.
| The density of water lb/U.S gallon | 8.345 lb/U.S gal |
| The density of water g/mL | 1 g/mL |
| The density of water g/cm3 | 1 g/cm3 |
| The density of water kg/m3 | 1000 kg/m3 |
| The density of water lb/ft3 | 62.4 lbs/ft3 |
| Unit weight of water | app 1 g/cm3 at 25 degrees Celsius |
| viscosity of water | 0.01 poise or 0.001 Pa.s (Pascal seconds) at 20 degrees Celsius |
| the specific gravity of water | 1 at 4 degrees Celsius (no units) |
| a cubic foot of water weight | 62.48 pounds at room temperature. |
Table of Contents
What is density?
Density refers to the amount of substance per unit volume. It is the mass-to-volume ratio of the material. If we take equal parts wood and iron. We’ll find that iron is heavier than wood. This is since iron has a greater amount of substance than wood.
Density (ρ) formula = mass (m) of substance ÷ volume (v) of substance
The density of water in lbs/U.S. gal
The density of water (ρwater) is around 8.345 lbs/U.S. gal. However, this value varies depending on the temperature and impurities in the water.
Common units of ρwater are grams per milliliter (1 g/ml), grams per cubic centimeter ( g/cm3), and pounds per cubic foot (lb/ft3). At 4°C, the density of fresh water on Earth is generally understood to be 1000 kg/m3.
Weight of Water
The weight of a gallon of water depends upon storing the temperature of the water, For the sake of the question, ‘How much does a gallon of water weigh?’, we are going to focus on the weight of water at 62 °F (17 °C).
1 US gal of water = 8.345 pounds = 3.785 kg (at 17 °C).
1 Imperial gal of water = 10.02 pounds = 4.545 kg (at 17 °C).
Weight of 1 liter (l) of pure water (at 4 °C) = 1 kilogram (kg).
Units of Gallon
There are three different Units of Gallon:
| Weight of a Gallon of Water | Fluid ounces | Liters | lbs | Kg |
| 1 US gallon of water at 17 °C | 128 | 3.785 | 8.345 | 3.785 |
| 1 Imperial gallon of water at 17 °C | 153.72 | 4.545 | 10.02 | 4.545 |
| 1 US dry gallon of water at 17 °C | 128 | 4.405 | 9.711 | 4.405 |
The specific weight of water
The specific weight of water is the weight of water per unit volume. It is represented by the symbol γ.
At 4°C, the specific weight of water on earth is 9.807 kN/m3 = 62.43 lbs/ft3.
Check the full article “Specific gravity of water”.
Calculating the specific weight of water
The density of water in g/ml = 1 g/ml
ρwater at 4°C (1 atm) is 1000 kg/m3
gravity (g) = 9.807 m/s2.
Weight (W) = mass (m) x gravity (g)
W = m x g
Specific weight (γ) = (ρ x volume x g)/volume
γwater = ρwater x g = 1000 kg/m3 x 9.807 m/sec2 = 9.807 kN/m3 ( 1 N = kg⋅m/s2)
Density Of Water in lbs/U.S. gal -Example Problem
The mass (m) of 8 liters of water is 8 kg. Its ρwater will be:
Volume = 8 liters = 8 x 10-3 m3
m=8 kg.
ρwater =mass/volume.
The density of water (g/ml) = 8kg/(8 x10-3 m3 )
= 1 g/ml = 8.3454 lbs/U.S gal
Why does ice float on water?
The less-dense stuff floats on top of the dense liquid.
Because the ρwater of ice is smaller than the ρwater of water, ice floats on water.
In general, a solid mass of a substance sinks when immersed in a liquid of the same substance. Solid atoms or molecules are more closely packed together than liquid atoms or molecules.
Therefore, the ρsolid > ρliquid > ρgas
There are some exceptions to this rule. Some materials like Silicon, germanium, bismuth, and water are less dense in solid form than in liquid form.
However, this exceptional behavior is never seen in nature for any of these materials except water because melting points are very high except for water. Check the full article “Melting point of water”.
To understand the concept of ice floating on water, we must first study the structure of water.
Every water molecule is made up of two hydrogen atoms bonded to one oxygen atom. Due to this molecular structure, water behaves abnormally when cooled.
It continues to contract and shrink in volume as it cools until it reaches 4°C.
Beyond this temperature, its volume expands and exceeds the starting volume.
Hence, its ρwater decreases and becomes more than the initial volume.
This enables ice to be lighter than water, allowing it to float.
Ice has about 8.3 percent lower density than water.
| Density value | Reference |
| The ρice is in the range 0.9167 -0.9168 g/cm3 at 0 °C and a standard atmospheric pressure of 101,325 Pa | “Definition of ICE”. www.merriam-webster.com. Retrieved 19 June 2018. |
| The ρwater is in the range of 0.9998 -0.999863 g/cm3 at the same temperature and pressure | The density of water explanation by USGS |
The Specific Gravity of Water
The specific gravity (G) of a substance is its density divided by the ρwater.
The specific gravity of water is one. It is the ratio of a material’s ρ with that of water at 4 °C (where it is most dense and is taken to have the value of 999.974 kg m-3).
There are no specific gravity units. It’s a ratio.
For something that floats, the specific gravity shows the proportion of that object below the water while floating.
Consider a cube of wood floating on water with a specific gravity value of 0.2.
The specific gravity of 0.2 indicates that 20% of the hardwood cube will be immersed in water.
What is Freshwater?
Freshwater (or freshwater) is any naturally occurring water safe to drink.
It has a dissolved salt content of fewer than 500 parts per million (ppm) of dissolved salts. Freshwater accounts for only 3% of the world’s water. Freshwater ecosystems cover less than 1% of the world’s total surface area.
The minimal freshwater requirements for human needs (per person) are 5 liters per day.
Properties of Freshwater
- Naturally occurring water is safe to drink.
- Mineral-rich waters such as chalybeate springs are included in the category of freshwater.
- Dissolved salts and other total dissolved solids are present in low quantities.
- Neither seawater nor brackish water is naturally occurring freshwater.
- Freshwaters from ice sheets, ice caps, glaciers, icebergs, bogs, ponds, lakes, rivers, and streams are also included in the category of freshwaters.
- It can only be restocked through the process of the water cycle, in which water from seas, lakes, forests, land, rivers, and reservoirs evaporates, forms clouds, and returns as precipitation.
Types of Freshwater
Freshwater can be broadly separated into two types, namely:
- Stagnant water (water that is still. some of its sources are lakes, marshes, and swamps)
- Flowing water (water that is constantly moving. Some of its sources are such as rivers and streams)
The density of Water in g/ml (Effect of Temperature)
The temperature of the water can affect the ρwater.
Even little changes in temperature have an effect on the weight of water.
When we heat water, the kinetic energy of the water molecules increases.
As a result, water molecules get more agitated and spread out.
As a result, the quantity of space required by each molecule is higher.
This results in a decrease in the ρwater
Therefore, the density of the cold water is greater than it would be in the hot water.
How much does a gallon of water weigh at its highest density?
Water has a maximum density of 39.2ºF or 4ºC.
At this temperature, a gallon of water weighs around 8.345 lbs.
If we turn the heating way up to 200ºF though, a gallon of water will weigh around 8.04 lbs.
At room temperature (70°F or 21°C), a US gallon of water weighs 8.33 lbs (3.78kg).
Factors Affecting Density of Water
- Temperature of water
- The purity of water
Summary
- The density of water in lbs/U.S gal is 8.345 lbs/U.S gal at 4 degrees Celcius.
- The density of cold water is higher than the density of hot water.
- Freshwater contains a concentration of dissolved salts less than 500 parts per million (ppm) of dissolved salts
Related Links
How Many Bottles of Water Equal a Gallon
Hydrogen Bond| Definition and Easy Explanation
Atmospheric Pressure| Pascal, And Newton
Mass vs Weight| 5 Easy Examples
Frequently Asked Questions (FAQs)
1. Why does oil float on water?
Oil floats on water because its density is lower than that of water. Density in liquids is defined as the amount of mass that may be filled into a cubic meter of volume. Water has a density of roughly 1000 kg/cubic meter, while oil has a density ranging from 800 to 960 kg/cubic meter.
2. What is a water molecule and how many hydrogen atoms are in a molecule of water?
Water is a substance that exists in gaseous, liquid, or solid phases and is made up of the chemical elements hydrogen and oxygen. It is one of the most abundant and necessary chemicals. At room temperature, it is a tasteless and odorless liquid with the critical capacity to dissolve many other compounds. Water’s capacity as a solvent is critical to living creatures.
A water molecule consists of two hydrogen atoms attached to the sides of a single oxygen atom.
3. Is boiling water a chemical change?
The boiling of water is not a chemical change as the water vapors retain the same molecular structure as liquid water.
Seawater is saline water with a higher concentration of dissolved salts. Its ρ is 1.0240 g/cm3 at 20°C and 1.0273 g/cm3 at 0°C at a constant salinity.
On cooling, water continues to contract and reduce in volume until 4°C.
Beyond this temperature, its volume increases and becomes more than the initial volume.
Hence, its ρwater decreases and becomes more than the initial volume.
This makes ice lighter than water, enabling it to float.
One US liquid gallon equals 16 cups and one US dry gallon equals 18.61 cups. One cup is one-half a US pint (236.6 ml). For details, check out the article How Many Cups in a Gallon? Cups to Pints, Quarts, and More
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