1. Chemistry XXI Unit 1 How do we distinguish substances? Module 2: Modeling Matter DISCUSSION Central goal: To explain the diversity in properties and behaviors of the different substances in a system based on the particulate model of matter.

2. Chemistry XXI Explain The particulate model of matter can be used to explain a variety of phenomena in our surroundings. Let’s see how good you are at building these types of explanations. Why do water puddles eventually disappear, given that T never reaches 100 o C? Let′s Think!

3. Chemistry XXI Explain Not all of the particles in a substance move at the same speed at a given temperature. Faster particles at the surface of the liquid are constantly escaping and being blown away. What is the difference between a substance getting wet and being dissolved in a liquid at the particulate level? Let′s Think!

4. Chemistry XXI Explain When something is wet, the solvent molecules can penetrate and “stick” to the molecules of the material, but the interactions are not strong enough to separate one from the other.

5. Chemistry XXI This happens when you put food coloring on chalk and put one extreme of the chalk on rubbing alcohol. How do you explain it using the particulate model of matter? Let′s Think!

6. Chemistry XXI Chromatography Different substances interact more or less strongly with both the solvent (rubbing alcohol) and the substrate (chalk), thus moving at different speeds.

7. Chemistry XXI T int = T ext P int = P ext T int > T ext P int = P ext Heat up T int = T ext P int < P ext Cool down How would you explain the phenomenon shown in this video using the particulate model of matter? Let′s Think!

8. Chemistry XXI Analyze How many phases are present in this system? How many elements and compounds are in each phase? How would you separate the different components? What would happen if T increases to 90 o C? Hexane (T b = 80.7 o C) T = 20 o C P = 1 atm

9. Chemistry XXI Analyze How many phases are present in this system? 3 PHASES  2 LIQUIDS, 1 GAS How many elements and compounds are in each phase? L1  1C (H 2 O) L2  2C (C 6 H 14, H 2 O); 1E (N 2 ) G  2E (N 2, O 2 ) How would you separate the different components? Use a separatory funnel; distillation What would happen if T increases to 90 o C? C 6 H 14 would go to the gas phase Hexane (T b = 80.7 o C) T = 20 o C P = 1 atm

10. Chemistry XXI Predict In which of the phases: Are the intermolecular forces strongest? Is the average potential energy per particle the lowest (most negative)? Is the average particle speed the highest? Is the average kinetic energy per particle the lowest? Which of the two main substances, water or hexane, has the greater vapor pressure? Hexane (T b = 80.7 o C)

11. Chemistry XXI Predict In which of the phases: Are the intermolecular forces strongest? L1 rich in H 2 O Is the average potential energy per particle the lowest (most negative)? L1 rich in H 2 O Is the average particle speed the highest? L1 rich in H 2 O Is the average kinetic energy per particle the lowest? The same in all phases (same T) Which of the two main substances, water or hexane, has the highest vapor pressure? Hexane Hexane (T b = 80.7 o C) T = 20 o C P = 1 atm