Which of the following are pure substances and which are mixtures? a. table sugar b. distilled water c. soft drinks d. oxygen gas (in tank) e. human breath
The Correct Answer and Explanation is :
Let’s go through each of the substances listed and classify them as either a pure substance or a mixture:
a. Table Sugar (Sucrose) – Pure Substance
Table sugar, or sucrose, is a compound consisting of carbon (C), hydrogen (H), and oxygen (O) atoms in a fixed ratio. It is chemically uniform throughout and does not vary in composition. It is classified as a pure substance because it is made up of a single type of molecule, specifically sucrose molecules.
b. Distilled Water – Pure Substance
Distilled water is water that has been purified through a process of distillation, which removes impurities, salts, and other substances. It is composed solely of H₂O molecules and does not contain any other components. Therefore, distilled water is considered a pure substance because it consists only of one type of molecule and has a uniform composition.
c. Soft Drinks – Mixture
Soft drinks are mixtures because they consist of several different substances, including water, sugars (such as sucrose or high-fructose corn syrup), flavorings, carbonation, and other additives. These components are not chemically bonded but physically mixed, and their proportions can vary from one brand or type of soft drink to another. This variability in composition makes soft drinks a mixture.
d. Oxygen Gas (in tank) – Pure Substance
Oxygen gas (O₂) in a tank is a pure substance. It consists of only oxygen molecules, each containing two oxygen atoms bonded together. While oxygen can exist in different forms (such as O₃ or ozone), oxygen gas in a tank typically refers to pure O₂ and is homogeneous in nature.
e. Human Breath – Mixture
Human breath is a mixture because it contains a variety of gases, including oxygen, carbon dioxide, nitrogen, and trace amounts of other gases such as water vapor and argon. These components are not chemically combined but are simply mixed together in varying proportions, which makes human breath a mixture.
Summary:
- Pure substances: Table sugar, distilled water, oxygen gas.
- Mixtures: Soft drinks, human breath.
In chemistry, a pure substance is a material made up of only one type of atom or molecule, whereas a mixture contains two or more different substances physically combined, without any chemical bonding between them.