Substances, Mixtures, and Solubility Chapter 21

What is a solution? O Substance – matter that has the same fixed composition and properties O Cannot be broken down by simple physical processes O Are bonded O Examples – molecules, compounds

Mixtures O Mixtures are combinations of substances not bonded together O Can be separated by physical processes O Heterogeneous – substances are not evenly mixed together (seeds in a watermelon) O Homogeneous – substances are evenly mixed together (lemonade) O All homogeneous mixtures are called solutions

Solutions O Molecules spread out evenly O Substance that dissolved is the solute O Substance that dissolves the solute is the solvent

Solids from Solutions O Crystallization – solid solute comes back out of a solution through physical means O Example – salt crystal comes out of a salt water solution when the water evaporates O The solid that comes out of the solution has not been “created”

Solids from Solutions O Precipitate – a solid created as a result of a chemical reaction in a solution O Example – chunky milk O The solid that comes out of the solution was created by the reaction

Types of solution O Liquid – liquid : vinegar, water is the solvent and acetic acid is the solute O Liquid-gas : carbonated beverage, water is the solvent and carbon dioxide is the solute O Liquid – solid : saltwater, water is the solvent and salt is the solute O Solid – solid : steel, iron is the solvent and carbon is the solute

Section 1 Review O A substance is either an element, molecule or a compound. Examples may include water or elements, such as oxygen. A mixture is two or more substances mixed together. Examples may include salt water or lemonade. Substances are chemically bonded but mixtures are not.

Section Review O The tops of carbonated beverage cans are usually made from a different alloy than the pull tab because the tab must be stronger so that it will open the can without breaking.