Properties and Changes of Materials - Separating mixtures (filtering, sieving, and decanting)
Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
A mixture consists of two or more substances that are physically combined but not chemically bonded, meaning they can be separated using physical methods.
Sieving is a method used to separate a mixture of solids with different particle sizes. Smaller particles pass through the holes in the sieve, while larger particles remain behind.
Filtering (Filtration) is used to separate an insoluble solid from a liquid. The liquid that passes through the filter paper is called the filtrate, and the solid trapped is the residue.
Decanting is the process of separating a liquid from a settled solid or another immiscible liquid by carefully pouring the top layer off. It is often used when the solid is heavy and sinks to the bottom, such as sand in .
Insoluble substances are materials that do not dissolve in a solvent. For example, sand is insoluble in , making it possible to separate them via filtration or decanting.
The choice of separation method depends on the physical properties of the materials, such as particle size, solubility, and density.
📐Formulae
💡Examples
Problem 1:
A student has a mixture of flour and dried pasta shapes. Which method should they use to separate them, and why?
Solution:
The student should use sieving.
Explanation:
Flour has very small particles, while pasta shapes are much larger. When placed in a sieve, the flour particles will pass through the mesh, leaving the larger pasta shapes behind.
Problem 2:
Explain how to separate a mixture of chalk powder () and water () to obtain clean water.
Solution:
The best method is filtering.
Explanation:
Chalk is insoluble in water. By pouring the mixture through filter paper in a funnel, the chalk () acts as the residue and stays on the paper, while the clean passes through as the filtrate.
Problem 3:
After washing some rice, the rice settles at the bottom of the bowl of water. How can you remove the water without using any equipment like a sieve or filter?
Solution:
The method used is decanting.
Explanation:
Because the rice is denser than and insoluble, it settles at the bottom. You can carefully tilt the bowl to pour the water out while keeping the solid rice at the bottom.