Properties of States of Matter: Diffusion and Solubility

Introduction

• Focus on article number one in unit one of Chemistry, Excel International GCSE
• Chapter questions: Numbers 4 to 6 on pages 12 and 13

Diffusion

• Definition: The spreading out of particles in a gas or liquid.
• Process: Particles move from high concentration to low concentration until equalized.
• Example:
  • Two jars: One with bromine (dark brown) and one with air.
  • When the glass lid is removed, both gases mix through diffusion.
• Comparison:
  • Gases: Diffusion occurs rapidly.
  • Liquids: Diffusion is slower due to less particle movement and more collisions.

Solution

• Components:
  • Solute: Substance that dissolves (solid, liquid, or gas).
  • Solvent: Substance in which the solute dissolves (most commonly water).
  • Solution: Mixture of solute and solvent.
• Saturated Solution: Contains maximum dissolved solute at a specific temperature, with undissolved solute present.
• Solubility: The maximum mass of solute that dissolves in 100 grams of solvent at a specified temperature.
  • Example: Sodium chloride solubility in water at 25°C is about 36 grams per 100 grams of water.
• Solubility Formula:
  • Solubility = (Mass of solute / Mass of solvent) x 100

Solubility Curves

• Solubility changes with temperature, can be graphed.
• Example:
  • Potassium chloride vs. potassium nitrate in 100 grams of water at varying temperatures.
• Curves illustrate differences in solubility between different solutes.

Chapter Questions

Question 4

• Reaction between ammonia (NH3) and hydrogen fluoride (HF) forms ammonium chloride (NH4Cl) as a white solid.
• Diffusion Experiment:
  • Ammonia and hydrochloric acid (HCl) gases create a white ring due to diffusion.
  • Reason for Delay in Ring Formation:
    • Diffusion is slow in liquids.

Question 5

• Process of Dissolving: Sodium chloride in water forms a solution where water is the solvent and sodium chloride is the solute.
• At 50°C, solution may become saturated and sodium chloride crystals may form.

Question 6

• Measured solubility of sodium chlorate at different temperatures:
  • 0°C: 3g
  • 20°C: 8g
  • 40°C: 14g
  • 60°C: 23g
  • 80°C: 38g
  • 100°C: 55g
• Graphing: Plot temperature on the x-axis and solubility on y-axis.
• Finding Solubility at 50°C: Approx. 18 grams.
• Maximum Mass Calculation: Using the solubility formula for 40g of water at 30°C, the answer is 4 grams of sodium chlorate.
• Crystal Formation: Crystals will form at a specific temperature when cooled.
  • If cooled to 17°C, additional calculations needed for total mass of formed crystals.

Conclusion

• Review and practice the concepts of diffusion and solubility.
• Assignments and further questions to be discussed in the next session.