Download Colligative Properties: Understanding the Impact of Solutes on Freezing and Boiling Points and more Study notes Chemistry in PDF only on Docsity! Colligative Properties 2018.notebook 1 April 09, 2018 Mar 114:12 PM Colligative Properties Aim: To observe and explain the affect that a solute has on colligative properties (freezing and boiling points) Mar 114:18 PM DO NOW • Why do you put salt in water when cooking pasta? • Why do you put rock salt down on the roads when its icy? Mar 114:18 PM DEMO‐ Boiling Point of Water Mar 114:18 PM COLLIGATIVE PROPERTIES AND FREEZING POINT • In terms of particle arrangement, explain what occurs when a substances freezes. • How is the presence of salt molecules affecting the freezing process of water? • What will this do to the amount of energy that must be lost to freeze the water? • How will the salt affect the freezing point of water? • The particles move closer together as they freeze. • The salt molecules are blocking the water molecules from freezing together. • This increases the amount of potential energy that must be lost to freeze. • The freezing point decreases. Colligative Properties 2018.notebook 2 April 09, 2018 Mar 114:18 PM COLLIGATIVE PROPERTIES AND BOILING POINT • In terms of particle arrangement, explain what occurs when a substance boils. • How are the presence of salt molecules affecting the boiling process of water? • What will this do to the amount of energy that is required to boil the water? • What will the requirement for more energy do to the boiling point? • The particles move farther apart as they vaporize. • The salt molecules are blocking the water molecules from boiling and escaping • This increases the amount of potential energy that must be absorbed to boil • The boiling point increases. Mar 114:18 PM Concentration, Dissocation and Colligative Properties • According to the diagrams above, which compound dissociates into ions? • Complete the dissolving equations for the compounds below. If dissociation occurs, write the individual ions and their charges. C6H12O6 (aq) à NaCl (aq) à • Sodium chloride Na+ (aq) + Cl‐ (aq)C6H12O6 (aq) NO DISSOCIATION; Covalent bonds Mar 114:18 PM Concentration, Dissocation and Colligative Properties Which of these compounds would cause a greater change in the boiling point or freezing point of a substance, 1 M NaCl or 1 M C6H12O6? Explain your answer in terms of particle quantities and concentrations. (Hint: Think about dissociation) The 1 M NaCl solution because it dissociates into ions and yields more particles in solution to cause more interference with the water boiling or freezing. Feb 2210:18 AM What affects colligative properties? The addition of any solute to a solution will increase the boiling point and decrease the freezing point. This is because the solute particles block the water molecules from escaping as a gas when boiling and from moving together to form a solid when freezing. As a result additional energy is required to boil (higher BP) and additional energy must be lost to freeze (lower FP).