Integrated Science Chapter 1 PDF

# Chapter 1: The Role of Solutions and Concentrations in the Movement of Water and the Distribution of Living Organisms ## Lesson Eight * In this lesson, we will study: * Aqueous solutions * Colligative properties of water * You may have noticed that the water in water bodies is not pure, but it...

# Chapter 1: The Role of Solutions and Concentrations in the Movement of Water and the Distribution of Living Organisms ## Lesson Eight * In this lesson, we will study: * Aqueous solutions * Colligative properties of water * You may have noticed that the water in water bodies is not pure, but it is a mixture of water and several dissolved or suspended substances. * The concentration of these dissolved substances affects directly: * Properties of water. * Water currents. * The distribution of marine living organisms at different depths. ## Aqueous solutions * **The solute** * It is the dissolved substance in solvent which exists in a smaller quantity. * **The solvent** * It is the main component of solution in which the other substances (solute) dissolve and it exists in a greater quantity. * **Solution** * It is a homogeneous mixture of a solvent and a solute. * **In the aquatic environment:** * The solvent is usually water. * The solute is salts or other substances. * **Concentration** * It is the amount of solute in a certain amount of solvent. | | By Time | By time | |---|---|---| | Diffusion of potassium permanganate (solute) in water (solvent) | Diluted solution of potassium permanganate | Concentrated solution of potassium permanganate | ## The effect of concentration on water density * The density of solution is directly proportional to the concentration of the solute, the higher the concentration of the dissolved substance (solute) in water, the higher the density of solution and vice versa. **So** * The density of salty water in seas and oceans * The density of fresh water in rivers and freshwater lakes * Changes in water density of the aquatic environment can lead to different movements of water, such as vertical currents that carry organisms to different depths or to the surface. ## Choose the correct answer: The opposite graph shows four different masses of (NaCl) salt dissolved in equal masses of water, which of the following solutions has the highest density? * A * **C** * B * D ## The opposite figure shows four different solutions of the same solute, arrange these solutions from the highest concentration to the lowest concentration. * **D** * **C** * **B** * **A** ## The colligative properties of solutions * Some properties of solutions differ from the properties of pure solvents (liquids) forming them at the same conditions, these properties are called the colligative properties of solution. ## The colligative properties of solution * They are properties of the solution that depend on the number of solute particles (ions or molecule) in the solution, not on its type. | 1 | 2 | 3 | 4 | |---|---|---|---| | Lowering of the solution vapor pressure | Colligative properties of solutions | Elevation of boiling point | Osmotic pressure (It was studied in lesson 4) | ## 1 Lowering of the solution vapor pressure * At a certain temperature, the volume of water in an open container decreases over time as a result of evaporation of water molecules on the surface. * When a certain volume of water is placed in a closed container, some water vapor molecules return from the air to the surface, which is known as condensation. * When the rate of the evaporation process is equal to the rate of condensation, this is known as (the dynamic equilibrium) between the liquid and its vapor. ## Vapor pressure * It is the liquid vapor pressure above liquid surface in a closed container, when the liquid and its vapor are in dynamic equilibrium at a certain temperature. ## Dynamic equilibrium * It is an equilibrium between the evaporation rate of the liquid and the condensation rate of its vapors at a certain temperature in a closed container. * The vapor pressure of pure water differs from that of solutions, where : | In pure water | In solution | |---|---| | The molecules of liquid surface consists of | The molecules of liquid surface consists of | | Water molecules only | Water molecules and some solute molecules | ## Forces that water molecules must overcome to be liberated from the surface | Pure water | Solution | |---|---| | ① Attraction forces among water molecules to each other. | ① Attraction forces among water molecules to each other. | | ② Attraction forces resulting from the hydrogen bonds caused by the polarity of water molecules. | ② Attraction forces resulting from the hydrogen bonds caused by the polarity of water molecules. | | | ③ Attraction forces between water molecules and solute molecules. | ## Where * The attraction forces between solvent molecules to each other is **Weaker than** * The attraction forces between solvent and solute molecules * So, * The vapor pressure of pure solvent is * **Greater than** * The vapor pressure of the solution ## From the previous, it is concluded that * The vapor pressure of the solution is usually less than that of pure water (solvent) that is forming it. ## Note: * The decrease in the liquid vapor pressure of a solution is directly proportional to the number of solute molecules or ions in the solution. ## For illustration only * The liquid surface area that is exposed to air doesn't affect the liquid vapor pressure at the same temperature.