Unit 2, Lesson 2.5 - Suspensions and Colloids

Unit 2, Lesson 2.5 - Suspensions and Colloids

Lesson Outline:
1. Suspensions
2. Colloids
3. Properties of Colloids
4. Summary: Solution, Suspension, Colloid

1. Suspensions & Colloids (Unit Two, Lesson 2.5) By Margielene D. Judan

2. Lesson Outline Suspensions Colloids Properties of Colloids Summary: Solution, Suspension, Colloid

3. 3 Types of Mixtures Solutions Suspensions Colloids

4. Suspensions cloudy and heterogeneous. Solute doesn’t dissolve and settle at the bottom Large particles (can be filtered)

5. The solute doesn’t dissolve. If you leave the mixture for a time, the sand particles will settle at the bottom.

6. Colloids Between a solution and a suspension Molecules are bigger than in a solution but smaller than in a suspension Components doesn’t separate out

7. Colloids vs. solutions Both solutions and colloids have a homogeneous appearance. But colloids can be determined by its light-scattering effect .

8. Colloids vs. solutions Solution Colloid Light-scattering

9. Colloids vs. solutions Solutions cannot scatter light because the particles are too small. Light-scattering is known as “Tyndall effect”.

10. Colloids Colloids are not only for liquid mixtures. The medium could be solid, liquid or gas, and the dispersed substance can also be solid, liquid or gas.

11. Solution (left); Colloid (right); Notice their difference when light passes through .

12. Properties of Colloids Tyndall effect Brownian movement Adsorption

13. 1. Tyndall Effect Known as “light scattering” Discovered by an Irish, John Tyndall

14. Tyndall effect in the sky; it happens when large particles are dispersed in the air.

15. Tyndall effect in the morning.

16. 2 . Brownian movement Continuous, random motion of colloidal particles Particles collide Discovered by an English botanist, Robert Brown

17. Continuous, random motion of colloidal particles (notice the blue lines)

18. Q.) If the molecules are larger than of a solution, why do molecules don’t settle down like suspension?

19. A .) Electric charges on the particles repel each other and prevent them from combining to larger particles. But heating destroys a colloid because it destroys the electrostatic charges, making them settle down the bottom.

20. 3. Adsorption The binding of molecules to a surface It is different from absorption. (ex. Activated carbon – binds molecules to purify)

21. Summary: Solution, Suspension, Colloid

22. Assignment: Bring a periodic table ON OUR NEXT MEETING .

23. Answer THIS in a whole sheet of paper. How are colloids important to us? Cite some of its importance. How does it help or benefit you in daily life? (refer to p. 62 for some details) Minimum of two paragraphs (10 pts)

24. Sources: Science Links 7 http://www.edinformatics.com/math_science/solutions_suspensions_colloids.htm