Material World
Particle Theory Matter is anything that has volume and mass. The particle model is a scientific model based on the idea that matter is made up of small particles. Matter is also organized into 3 phases Solid Liquid Gas
Particle Theory
Atoms and Molecules An atom is the smallest particle of matter. It cannot be divided by chemical means. A collection of atoms with the same number of protons and electrons are elements A molecule is a group of two or more atoms held together by chemical bonds.
Atom
Molecule
Molecule
Molecule
Mixtures and Pure Substances A mixture consists of at least 2 different substances This means that it has two different types of particles They can either be homogeneous or heterogeneous. A pure substance consists of only one substance, it contains only one type of particles. A pure substance can either be compounds or elements
Mixtures A heterogeneous mixture is made up of at least two substances that can be distinguished with the naked eye. A homogeneous mixture is made up of at least two substances that cannot be distinguished with the naked eye. Colloids are a specific type of homogeneous solution which can be distinguished with a microscope Milk is an example of this where the fat globules can be seen with a microscope.
Heterogeneous
Homogeneous
Colloids
Solutions Solutions are homogeneous solution that cannot be distinguished under a microscope. There are two components Solute is dissolves in another substance. Solvent is what is dissolving a solute.
Properties of Pure Substances Pure substances have characteristic properties. A characteristic property is one that helps identify a pure substance or the group which the pure substance belongs. Characteristic properties can be divided into two categories Physical Chemical
Physical Properties Physical properties are characteristics which help us identify a pure substance without changing the nature of the substance in the process. There are 4 which will be discussed in class: Melting point Boiling point Density Solubility
Melting and Boiling Point The melting point of a substance is the temperature at which it passes from a solid to a liquid. The boiling point is the temperature where the substance passes from a liquid to a gas. These are expressed in C Different substances have different melting/boiling points.
Density Density represents the mass per unit of volume. Density is calculated using the following formula ρ = m / V ρ represents density m represents mass V represents volume Density is typically represented in g/ml
Density Example You have 25 ml of an solution It has a mass of 32 g Density of the substance is 32 g/25 ml ρ = 1.28 g/ml
Solubility The solubility of a substance is the maximum amount of solute that can be dissolved in a given volume of solvent. This can be expressed in g/l or in % % m/v, % m/m, % V/V Solubility is greatly affected by the temperature of the liquid Higher temp = Higher solubility
Solubility
Saturation Saturation is defined as a solution which has reached a maximum solubility. A solution can become supersaturated. This involves heating a solution, saturating it, and then cooling it down. Since solubility decreases as temperature decreases, the solution now contains too much solute.
Properties of Solutions A given solution has a concentration. This can be given in one of 4 forms g/l A number of grams of solute per liter of solution % m/v A number of grams of solute per 100 ml of solution % V/V A number of ml of solute per 100 ml of solution % m/m A number of grams of solute per 100 g of solution
Calculating Concentration Concentration in g/l can be calculated with the following equation C = m / V where C = Concentration m = mass of the solute in g V = Volume of the solution in L
Dilution Dilution is a laboratory technique that involves decreasing the concentration of a solution by adding solvent. If you are given a solution with a concentration of 4 g/ml and you quadruple the volume, you will end up with a solution of 1 g/ml. It is important to remember that the amount of solute does not change in a dilution, only the solvent.
Dilution The equation for dilution is as follows C1 V1 = C2 V2, where: C1 is the concentration of the original solution V1 is the volume of the original solution C2 is the concentration of the new solution V2 is the volume of the new solution
Dilution You have 125 ml of a solution of NaCl with a concentration of 14 g/l You add 375 ml of water to the solution. What is the new concentration? Identify which variables you know and start calculating.
Dilution C1 = 14 g/ml V1 = 125 ml C2 = x V2 = 125 ml + 375 ml = 500 ml 14 g/ml 125 ml = x 500 ml x = 14 g/ml 125 ml / 500 ml = 3.5 g/ml