A gram is a metric unit of mass. It is equal to 1/1000th of a kilogram. When we think about the mass of small objects, like a paperclip or a raisin, we often use grams as the unit. But what exactly makes up 1 gram? Let’s take a closer look and break it down.
Defining a Gram
As mentioned above, a gram is defined as exactly 1/1000th of the mass of a kilogram. The kilogram is the base unit of mass in the metric system. To define a kilogram, in the late 19th century, scientists created a physical cylinder made of platinum-iridium alloy that weighed exactly 1 kilogram. This prototype kilogram, called the International Prototype Kilogram or IPK, was then used to create exact copies which were sent around the world to define the kilogram in different locations.
The IPK cylinder was used for over 100 years to define the kilogram. All other metric units, like the gram, were based off the mass of this physical prototype. However, in 2019, the definition of the kilogram shifted to be based on fundamental physical constants instead of a physical artifact. Now, 1 kilogram is defined by setting the Planck constant to be exactly 6.62607015×10−34 kg⋅m2/s. Using this constant, the mass of 1 kilogram can be precisely reproduced without needing a physical prototype.
The 2019 Redefinition
The decision in 2019 to redefine the kilogram based on physical constants was made to improve precision and universality. Over time, the IPK cylinder had fluctuated slightly in mass due to surface contamination and other damage. This meant the definition of the kilogram was not perfectly stable. Basing the kilogram on fundamental constants creates a more precise and consistent definition that does not depend on a physical object.
What is a Gram Made Up Of?
Now that we know a gram is defined as 1/1000th of the mass of a kilogram, what exactly constitutes that mass? Here are the basic components:
- Atoms – At the most fundamental level, the mass of all matter is determined by the number and type of atoms it contains. The atom is the basic unit of a chemical element, comprising a dense nucleus surrounded by a cloud of electrons. Different elements have atoms of differing masses; a hydrogen atom is much lighter than an iron atom, for example. The number and identity of atoms in an object determine its mass at the atomic scale.
- Molecules – Atoms connect together to form molecules and more complex structures. The molecules in a substance contribute to its overall mass. For instance, water molecules each contain two hydrogen atoms bonded to one oxygen atom. The mass of a water molecule comes from the mass of these component atoms.
- Bulk Matter – When many atoms and molecules are assembled together, they make up the bulk matter we can observe and interact with on a large scale. The gram is a unit defined to describe macroscale mass as we experience it regularly. Although mass originates at the atomic level, the gram abstracts away the complex details of individual atoms and molecules to simply measure the total mass present.
The Role of Atoms
To summarize, atoms are the basic building blocks that constitute all matter and contribute fundamental mass. The particular atoms, and how they are assembled into molecules and larger structures, determine the mass of the resulting bulk material. By precisely defining the kilogram based on Planck’s constant and the mass of atoms, all macroscale mass units can be connected back to the atomic origins of mass.
Some Examples of 1 Gram Objects
Let’s make things more concrete by looking at some examples of objects that weigh approximately 1 gram:
- A paperclip
- A small raisin or grape
- A cubic centimeter of water (1 mL)
- A 5 mm cube of aluminum
- A U.S. dollar bill (1 g paper)
- 5 standard aspirin tablets
- A small piece of sliced cheese
- 2 standard size paperclips
As you can see, 1 gram represents a very small mass that we encounter frequently in everyday objects. It takes 1,000 objects of 1 gram to make up 1 kilogram. Given how light a gram is, it’s no wonder we need thousands of them to reach a kilogram!
Mass vs Volume
When thinking about these examples, it’s important to distinguish mass from volume. For instance, 1 mL (1 cubic cm) of water has a mass of 1 gram, but a larger volume object like a penny has a mass of around 3 grams. Mass describes how much matter is present, while volume refers to the amount of 3-dimensional space occupied.
What Does 1 Gram Look Like?
It can be hard to visualize just how small 1 gram is. Here are some ways to picture it:
- A standard paperclip weighs about 1 gram.
- A packet of artificial sweetener typically contains around 1 gram.
- A standard wooden match weighs roughly 1 gram.
- A 1 gram cube of water would have sides just under 1 cm long.
- A U.S. dollar bill weighs about 1 gram.
As these examples illustrate, 1 gram is very light and takes up a tiny amount of space. It’s only about the weight of a small paperclip – something we consider to have almost no noticeable mass when we hold it.
Comparisons
To give more perspective:
- 10 grams is about the mass of a large paperclip.
- 100 grams is about the mass of a deck of playing cards.
- 500 grams is just over 1 pound.
As we scale up through orders of magnitude, we quickly get to masses that feel more substantial to us. But at just 1 gram, the mass is extremely small and delicate.
What Does 1 Gram Feel Like?
So we know what 1 gram looks like in various objects, but what does it feel like when you hold it in your hand? Here are some descriptions:
- Almost weightless and floating on your palm
- Similar sensation to holding a paperclip, plastic tip of a shoelace, or a penny
- Easy to make small movements and oscillations with tiny muscle forces
- Hardly noticeably unless you move it around – could balance it on a fingertip
- Can flick it through the air with minimal effort
In essence, 1 gram feels extremely light and insubstantial. You have to pay close attention to notice that you are holding or moving something of that mass. The sensation is akin to holding a tiny plastic fragment or paper snippet.
Force of Gravity
The small force you feel when holding 1 gram comes from Earth’s gravity acting on its mass. However, because the mass is so tiny, this gravitational force is only around 0.01 Newtons – similar in magnitude to the force needed to hold up a medium paperclip against gravity.
This sub-Newton level force is difficult for us to notice unless we concentrate on the fine sensations in our fingers tips. So while the gravitational force is certainly present, the effect on our sensory perception is minimal.
How Many Atoms Are in 1 Gram?
We know that at the smallest scale, mass originates from atoms. So how many atoms make up 1 gram? Let’s find out.
The two most common elements in ordinary matter are hydrogen and oxygen. A hydrogen atom has a mass of about 1.7 x 10-24 grams. An oxygen atom is heavier, with a mass of around 3 x 10-23 grams.
To determine the number of atoms in 1 gram, we divide the gram by the atomic mass:
- Hydrogen: 1 g / 1.7 x 10-24 g/atom = 5.9 x 1023 atoms
- Oxygen: 1 g / 3 x 10-23 g/atom = 3.3 x 1022 atoms
As you can see, it takes an enormous number of atoms to make up just 1 gram! This illustrates how tiny individual atoms really are.
Atoms and Molecules
It’s important to note these calculations look at individual atoms, rather than molecules. In reality, atoms join together to form molecules like water (H2O) that have more mass than a lone hydrogen or oxygen atom. On the order of 1022 molecules would make up a more realistic 1 gram mass of a substance.
Conclusion
To summarize, 1 gram represents an extremely small amount of mass, equal to just 1/1000th of a kilogram. This mass originates from a huge number of atoms, on the order of 1022 to 1023 for common elements. While we rarely think about the atomic composition of matter in our everyday lives, this connection to fundamental particles is what ultimately defines the mass of any object we encounter. So the next time you pick up a 1 gram item, take a moment to appreciate just how many tiny atoms had to come together to create that seemingly insignificant speck of material in your hand!