2.5 Colloids & Suspensions
Colloid
These are heterogeneous mixtures in which the solute particles are larger than those present in true solutions but not large enough to be seen by the naked eye. A colloid is a mixture with particles ranging in diameter, yet are still able to remain dispersed without settling at the bottom of the container. These are also known as colloidal dispersions because the substances remain dispersed and do not settle. The particles are large enough to scatter a beam of light, which is known as the Tyndall effect. The Tyndall effect is the main characteristic that distinguishes colloids from solutions, making them false solutions or colloidal solutions. Examples include starch, albumin, soap solutions, blood, milk, ink, jelly, and toothpaste.
Suspension
A suspension is defined as a heterogeneous mixture in which solid particles are spread throughout the liquid without dissolving. It is a mixture of undissolved particles in a given medium. The particles are large enough (greater than 1000 nm) to be seen with the naked eye. Examples include chalk in water (milky suspension), paints, and milk of magnesia (suspension of magnesium oxide in water).
Comparison of Solution, Colloids, and Suspension
| S.No | Solution | Colloids | Suspension |
|---|
| 1 | A homogeneous mixture of two or more components | A heterogeneous mixture of two or more components | A heterogeneous mixture of two or more components |
| 2 | Particle size is less than 1 nm, not visible to the naked eye | Particle size varies from 1-1000 nm, not visible to the naked eye | Particle size greater than 1000 nm, visible to the naked eye |
| 3 | Particles can pass through normal and ultra-filter paper | Particles can pass through normal filter paper but not ultra-filter paper | Particles cannot pass through normal or ultra-filter paper |
| 4 | Cannot scatter light (due to small size) | Can scatter light (Tyndall effect) | Can scatter light (Tyndall effect) |
| 5 | Does not separate | Does not separate | Separates or settles when stationary |
| Examples | Sea water | Milk | Muddy water |
Key Points
- Anything that has mass and occupies space is called matter.
- Plasma is an electrically charged gas, affected by electrical and magnetic fields.
- The property of an element to exist in different physical forms is called allotropy.
- An element is the simplest form of matter made up of the same type of atoms.
- A compound is a substance formed when two or more different atoms chemically combine.
- A homogeneous mixture of two or more components is called a solution.
- An aqueous solution is formed by dissolving a substance in water.
- A solution containing the maximum amount of solute at a given temperature is called a saturated solution.
- A solution containing a lesser amount of solute than required to saturate it at a given temperature is called an unsaturated solution.
- A colloid is a mixture with particles ranging between 1 and 1000 nanometers in diameter.
- A suspension is a heterogeneous mixture where solid particles are spread throughout the liquid without dissolving.
Review Questions
- Encircle the correct answer:
- (i) Anything that has mass and occupies space is called:
- (a) Liquid
- (b) Gas
- (c) Solid
- (d) Matter
- (ii) Following are states of matter:
- (a) Gas
- (b) Liquid
- (c) Solid
- (d) All of these
- (iii) Macroscopic properties are properties that can be visualized by:
- (a) the naked eye
- (b) microscope
- (c) electron microscope
- (d) telescope
- (iv) Matter can be described by both its:
- (a) physical properties and chemical properties.
- (b) physical properties
- (c) chemical properties.
- (v) A substance formed when two or more different elements combine chemically is called:
- (a) atom
- (b) compound
- (c) element
- (d) solution
- Give short answers:
- Can you write the formula of the carbon dioxide gas that we exhale?
- Define the element, compound, and mixture. Differentiate between compound and mixture.
- Differentiate between concentrated and dilute solution.
- Define the term Allotropes. Explain the allotropes of Carbon.
- What is the difference between Homogeneous and Heterogeneous solutions?
- Differentiate between colloids, suspension, and solution.
- If there are 18 protons in the Argon atom, what is the atomic number of Argon?
- Describe the state of matter with examples.
- Differentiate between the following:
- Colloids and Suspensions
- Elements and Compounds
- Concentrated and Dilute solutions
- Examine the concept of solubility.
- Think Tank:
- Why is a solution considered a mixture?
- How will you test whether a given solution is a colloid or a solution?
- Project:
- Create a poster that illustrates the various forms of matter in the student's everyday environment.