Yes, sugar is a pure substance, because is made up of only one kind of compound.
The article that follows explains what a pure substance is, what sugar is, and why sugar qualifies.
Why Is Sugar A Pure Substance?
What Is A Pure Substance?
The first step to understanding why sugar is a pure substance is understanding what a pure substance is.
A pure substance is a material that is made up of only one type of building block.
This building block can be an element (such as gold). If the building block is an element, then there are only atoms of that element in the material.
This building block can also be a compound.
A compound is made when two or more elements form chemical bonds to each other.
These compounds are the same in every instance, in the types of elements and in the structure of the components.
Water is a good example of a pure substance that has a compound as its building blocks.
The compound that is water is made of hydrogen bonded to oxygen. Two hydrogens connected to one oxygen. On repeat.
What Is Sugar?
To understand how and why sugar is a pure substance, we need to understand what sugar is.
Sugar is the informal name for sucrose. Sucrose is a molecule (not an atom or an element). It is formed from 12 carbons, 22 hydrogens, and 11 oxygens (C12H22O11).
You can also call the molecule that is sucrose a compound.
Why Is Sugar A Pure Substance?
Sugar is considered a pure substance because it is composed of a a compound, C12H22O11, on repeat.
There are no other elements or compounds that are needed to make up this substance.
That being said, if the sugar/sucrose is mixed up with other elements or changed by heat or a reaction, then it may no longer be considered a pure substance.
It just really depends upon whether the changed substance is still only made up of one kind of building block (element or compound).
Is Sugar A Mixture?
No, sugar is not a mixture. The substances that make up sugar are chemically bonded to each other, and cannot be easily separated without breaking those chemical bonds.
A mixture is a substance made up or more than one material, when those materials are physically combined. The materials can be separated back into their original substances, though they might not be able to be returned to their original form (like an egg, as an example).
The materials are not chemically bonded to each other.
Sugar is made up of carbon, hydrogen, and oxygen. These materials are chemically bonded to each other, and sugar does not exist if those chemical bonds are broken.
A good example of a mixture is beach sand, which is a granular material containing many different kinds of rocks and minerals. These materials are physically in the same space, but can be separated from each other without having to break chemical bonds.
Is Sugar A Compound?
Yes, sugar is a compound.
Chemically, a compound is formed when two or more elements form bonds to each other.
Sugar is formed when carbon, hydrogen, and oxygen atoms form bonds (C12H22O11).
Is Sugar An Element?
No, sugar is not an element.
An element is a substance which cannot be broken down into more simple parts.
For example, water is a substance that can be broken down into simpler parts. It is made when you connect hydrogen to oxygen. It can be made more simple by breaking the hydrogen and oxygen apart.
Like water, sugar can be broken down into smaller parts. It is composed of hydrogen, carbon, and oxygen bonded together.
These bonds can be broken, and the components can be separated.
Since sugar can be broken down into more simpler parts, it is not an element.
Is Sugar An Atom?
No, sugar is not an atom.
Sugar is a molecule. It is formed when several atoms of carbon, hydrogen, and oxygen form chemical bonds.
The substances that make up sugar are considered atoms, but each unit of sugar that is formed when the right combination of atoms bond to each other in the right shape is called a molecule.
You could also call sugar a compound.
Is Sugar A Lipid?
No, sugar is not a lipid.
While we generally think of a lipid as “fat,” chemically speaking, it is a macro biomolecule that is insoluble in water and soluble in non-polar solvents. (source)
Sugar is soluble in water. Consequently, sugar is not a lipid.
Is Sugar Dissolved In Water A Heterogeneous Mixture?
This depends on how much sugar is added to the water.
See also: Does Sugar Dissolve In Alcohol?
A heterogeneous mixture is one that is not consistent chemically throughout.
A homogeneous mixture is one that is consistent and the same throughout.
A certain amount of water can only dissolve a certain amount of sugar.
If you keep adding sugar to the water, the water will become saturated, and then sugar will not dissolve into the water.
Instead, it will fall to the bottom of the glass.
If the water is not saturated with sugar, then the water should be a homogeneous mixture.
But if the water is saturated with sugar, then there will be more sugar at the bottom of the container, and the mixture will be heterogeneous.
We suppose this will also depend on the size of the water container and how much sugar as been added, and also how long the water and sugar has been combined.
It can take time for the sugar to dissolve into the water and spread itself out evenly throughout the unit of water, especially if it is a significant amount of water, or the sugar is very little.
See also: Is Sugar a Mineral?