SOLUTIONS DAY 2

INTRODUCTION Did you ever hold a piece of candy on your tongue for a long period of time because you wanted to make it last? What happened?

INTRODUCTION It disappeared, right? That’s because most of your saliva is made up of water. Water is often called the universal solvent. There are not too many things that when placed in water will not eventually dissolve.

INTRODUCTION The electrical charges of water are what helps it separate the particles of a solute and spread them evenly throughout the water.

INTRODUCTION When a solute is added to a solvent the solute only splits if there is a greater attraction to the parts of the solvent than the forces holding the solute together.

INTRODUCTION If the attraction between the parts of the solute is too great it will not dissolve.

INTRODUCTION There are two types of solutions we are interested in, ionic solutions, and molecular solutions.

INTRODUCTION Ionic solutions, like salt water, form when an ionic compound is dissolved in a solvent, like water. The polar molecules surround the positive and negative particles of the salt and pull it apart. The particles are then spread throughout the solution by the water molecules.

INTRODUCTION A molecular solution, like sugar water, forms because the sugar molecules are pulled apart from each other by the attraction to the water molecules, and each sugar molecule bonds with a water molecule. The sugar molecules stay intact. The sugar molecules are then spread throughout the solution by the water molecules.

OBJECTIVES Explain why water is called the universal solvent. Differentiate between molecular and ionic solutions.

IN QUESTION What are the parts of a solution? Solute Solvent

VOCABULARY Polar molecule – Molecule in which one end has a positive charge and the other end has a negative charge. Molecular solution – the molecule stays intact but bonds with the molecules of the solvent and then spreads throughout the solvent.

VOCABULARY Ionic solution – the ionic bonds of the molecule are broken by the greater attraction to the solvent and the ions are pulled apart and spread throughout the solution.

NOTES Water molecules are polar. One end is positive the other end is negative. The oxygen end is negative. The hydrogen end is positive.

COPY THIS IN YOUR NOTES Polar molecule of water.

NOTES Greater attraction to polar molecules is what breaks down compounds in a solvent. The charged ends of a water molecule help separate particles of a solute. Once separated the particles are spread throughout the water.

NOTES Molecular solutions form when force of attraction between solvent molecules and solute molecules is greater than forces of attraction holding particles of solute together. Sugar water is a molecular solution.

EXAMPLE

NOTES Ionic solutions are formed when ionic compounds are added to water and the water pulls apart the ions making up the compound. Salt water is an ionic solution.

EXAMPLE

OUT QUESTIONS Will water dissolve in water? No. it only mixes. A substance is placed in water but does not dissolve. Explain why. It is insoluble.