Which of the following substances is a heterogeneous mixture?
A) sodium
B) baking soda
C) dextrose (a sugar) dissolved in water
D) salt and pepper in a glass
The correct answer and explanation is :
The correct answer is D) salt and pepper in a glass.
Explanation:
A heterogeneous mixture is a type of mixture where the components are not uniformly distributed and can be distinguished from one another. This differs from a homogeneous mixture, where the components are evenly mixed and appear uniform throughout. Let’s examine each of the options to understand why “salt and pepper in a glass” is the best choice for a heterogeneous mixture:
- A) Sodium: Sodium (Na) is an element, not a mixture. It is a pure substance, which means it is made up of only one type of atom. Pure substances, whether they are elements or compounds, are not considered mixtures and, therefore, cannot be classified as either homogeneous or heterogeneous mixtures. So, sodium is not a heterogeneous mixture.
- B) Baking Soda: Baking soda (sodium bicarbonate, NaHCO₃) is a pure compound, not a mixture. A compound is a substance made up of two or more elements that are chemically bonded. In the case of baking soda, the elements are combined in a fixed ratio, making it a homogeneous substance. Hence, baking soda is not a heterogeneous mixture.
- C) Dextrose (a sugar) dissolved in water: When dextrose dissolves in water, it forms a homogeneous mixture known as a solution. In this case, the sugar molecules are evenly distributed throughout the water, and you cannot distinguish between the water and the dissolved sugar. This even distribution qualifies it as a homogeneous mixture, not a heterogeneous one.
- D) Salt and pepper in a glass: This is a classic example of a heterogeneous mixture. When you mix salt and pepper together, the particles of each substance are not evenly distributed, and you can easily see and separate the two components. The salt and pepper are not chemically bonded and retain their individual properties. This makes the mixture heterogeneous because the components are not uniformly mixed.
In summary, a heterogeneous mixture contains visibly distinct components, and the mixture of salt and pepper in a glass meets this criterion. The other options either refer to pure substances or homogeneous mixtures.