Heterogenous (suspension ad colloids)

HETEROGENEOUS

1. HETEROGENOUS SUSPPENSIONS AND COLLOIDS

2. RECAP

3. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Suspensions Suspensions What is the difference between a suspension and a solution? A suspension ….

4. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Suspensions Suspensions What is the difference between a suspension and a solution? A suspension is a mixture from which particles settle out upon standing.

5. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. A suspension differs from a solution because the particles of a suspension are much larger and do not stay suspended indefinitely. Suspensions

6. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. A suspension differs from a solution because the particles of a suspension are much larger and do not stay suspended indefinitely. Suspensions The particles in a typical suspension have an average diameter greater than 1000 nm. By contrast, the particle size in a solution is usually about 1 nm.

7. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Suspensions A solution is a homogeneous mixture. Suspensions are heterogeneous because at least two substances can be clearly identified.

8. Suspensions The difference between a solution and suspension is easily seen when the type of mixture is filtered. The small size of the solute particles in a solution allows them to pass through filter paper. The particles of a suspension can be removed by filtration.

9. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Explain why a mixture of sand and water can be separated by filtration, but a mixture of salt and water cannot.

10. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Explain why a mixture of sand and water can be separated by filtration, but a mixture of salt and water cannot. A mixture of sand and water is a suspension, and a mixture of salt and water is a solution. The particles in the sand mixture are much larger than the ions in the salt mixture. The sand particles are too large to pass through filter paper; the ions are not.

11. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Colloids Colloids What distinguishes a colloid from a suspension and a solution?

12. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Colloids A colloid is a heterogeneous mixture containing particles that range in size from 1 nm to 1000 nm. The particles are spread, or dispersed, throughout the dispersion medium, which can be a solid, liquid, or gas.

13. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Colloids The first substances to be identified as colloids were glues. Some Colloidal Systems System Type Example Dispersed phase Dispersion medium Gas Liquid Foam Whipped cream Gas Solid Foam Marshmallow Liquid Liquid Emulsion Milk, mayonnaise Liquid Gas Aerosol Fog, aerosol Solid Gas Smoke Dust in air Solid Liquid Sols, gels Egg white, jelly, paint, blood, starch in water, gelatin

14. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Colloids Colloids have particles smaller than those in suspensions and larger than those in solutions.

15. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Colloids Colloids have particles smaller than those in suspensions and larger than those in solutions. These intermediate-sized particles cannot be retained by filter paper as are the larger particles of a suspension. They do not settle out with time.

16. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Colloids The Tyndall Effect You cannot see a beam of sunlight unless the light passes through particles of water (mist) or dust in the air. These particles scatter the sunlight. Similarly, a beam of light is visible as it passes through a colloid.

17. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Colloids The Tyndall Effect The scattering of visible light by colloidal particles is called the Tyndall effect . Flashlight Solution Colloid Suspension

18. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Colloids Suspensions also exhibit the Tyndall effect. The particles in solutions are too small to scatter light. Flashlight Solution Colloid Suspension

19. Colloids This table summarizes the properties of solutions, colloids, and suspensions. Properties of Solutions, Colloids, and Suspensions Property System Solution Colloid Suspension Particle type Ions, atoms, small molecules Large molecules or particles Large particles or aggregates Particle size 0.1 –1 nm 1 –1000 nm 1000 nm and larger Effect of light No scattering Exhibits Tyndall effect Exhibits Tyndall effect Effect of gravity Stable, does not separate Stable, does not separate Unstable, sediment forms Filtration Particles not retained on filter Particles not retained on filter Particles retained on filter Uniformity Homogeneous Heterogeneous Heterogeneous

20. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Key Concepts A suspension differs from a solution because the particles of a suspension are much larger and do not stay suspended indefinitely. Colloids have particles smaller than those in suspensions and larger than those in solutions. KEY CONCEPTS