PROPERTIES OF MATTER LAW OF CONSERVATION OF MATTER Matter cannot be created nor destroyed, it can only be changed from one form to another. Matter and energy are interchangeable according to E=mc 2 (E=amount of energy, m = amount of matter, c= a constant equal to the velocity of light) The Law of Conservation of Matter is why we must balance a chemical equation : 4Al + 3O 2 2Al 2 O 3 (reactants) (product) - The total number of atoms in the reactants is equal to the total number of atoms in the product. - Two pieces of matter cannot occupy the same space at the same time. Example: When you get into a bathtub filled with water, the water level rises (water displacement). Matter can be defined as anything that has mass and takes up space (volume). Mass is the amount of MATTER in an object Volume is the amount of space that the MATTER in an object takes up. Matter can exist in 4 states: 1. solid - has definite shape and volume. Example: ice, salt, wood. 2. liquid - has definite volume but no definite shape. Example: water, milk, mercury. 3. gas - has no definite volume or shape. Example: air, water vapor, CO2. 4. plasma - the state of matter that exists at high temperatures, it consists of electrically charged particles. Example: sun, nuclear fusion
Examples of changes of state: (these are considered physical changes) 1. evaporation - liquid to gas 2. condensation - gas to liquid 3. freezing - liquid to solid 4. sublimation - solid to gas 5. melting - solid to liquid water 6. deposition gas (vapor) to solid Relevant key terms: crystal - arrangement of the particles in a solid in repeating patterns. viscosity - the property of a liquid that describes how it pours. Density - is the mass of a substance per unit of volume or how tightly packed an object's atoms or molecules are. Less dense materials float on denser materials. Density of water (@4 o C) = 1 g/cm 3 Density is a physical property and intensive property. Density = mass/volume Density is expressed in grams per cubic centimeter (g/cm 3 ) or (g/ml) KINETIC THEORY OF MATTER - all matter is made up of tiny particles called molecules, these particles are in constant motion. SOLID LIQUID GAS Definite volume Definite volume No definite volume Definite shape No definite shape No definite shape NOTE: increasing temperature will increase the speed of molecules and result in an increase of kinetic energy.
CHEMICAL AND PHYSICAL PROPERTIES Physical property a quality of a substance that can beobserved or measured by using physical senses. Examples: color, mass, size, density, magnetic, melting point, boiling point, texture, shape. Chemical property the ability of a substance to undergo chemical reactions and to form new substances Examples: Was heat, light, sound, or some other form of energy generated? Did a reaction take place at all (if not, the materials are non-reactive - which is a chemical property)? Were gases formed? Was it endothermic or exothermic? The chemical properties of an element are determined by the number of valence electrons it has. CHANGES IN MATTER - PHYSICAL AND CHEMICAL Physical change: change in physical properties - a change in shape, size, or state without a change in actual composition. - Example: breaking a rock, melting ice, evaporation, freezing water. Chemical change: Change in which a substance becomes another substance with different properties. - Example: souring of milk, silver tarnishing, electrolysis of water - an energy change always accompanies a chemical change - loss or gain of heat, light, or some other form of energy.
SOME PHYSICAL PROPERTIES OF MATTER: A. BIOLING POINT - The temperature at which a substance changes from a liquid to a gas. B. CONDENSATION POINT - The temperature at which a substance changes from a gas to liquid; same temperature as boiling point. C. DENSITY - The mass of a specific volume of substance. D. FREEZING POINT - The temperature at which a substance changes from a liquid to a solid; same temperature as melting point. E. MELTING POINT - The temperature at which a substance changes from a solid to a liquid. F. RESISTANCE - The opposition of a substance has to the flow of electric current. G. SOLUBILITY - The degree to which a substance will dissolve in a given amount of another substance, such as water. Physical properties of matter are categorized as either Intensive or Extensive: Intensive - Properties that do not depend on the amount of the matter present and are used to identify a substance. o Color o Odor o Luster - How shiny a substance is. o Malleability - The ability of a substance to be beaten into thin sheets. o Ductility - The ability of a substance to be drawn into thin wires. o Conductivity - The ability of a substance to allow the flow of energy or electricity. o Hardness - How easily a substance can be scratched. o Melting/Freezing Point - The temperature at which the solid and liquid phases of a substance are in equilibrium at atmospheric pressure. o Boiling Point - The temperature at which the vapor pressure of a liquid is equal to the pressure on the liquid (generally atmospheric pressure). o Density - The mass of a substance divided by its volume
o Extensive - Properties that do depend on the amount of matter present and cannot be used to identify a substance. Mass - A measurement of the amount of matter in a object (grams). Weight - A measurement of the gravitational force of attraction of the earth acting on an object. Volume - A measurement of the amount of space a substance occupies. Length- A measurement of distance from poit A to point B PURE COMPOUNDS and MIXTURES A pure substance is either an element or a compound that has a constant composition with fixed ratios of elements. A MIXTURE is a combination of two or more substances that are not chemically united and do not exist in fixed proportions to each other. Most natural substances are mixtures. A mixture can be physically separated into pure compounds or elements. HOMOGENEOUS MIXTURES : The prefix "homo"- indicates sameness A homogeneous mixture has the same uniform appearance and composition throughout. Many homogeneous mixtures are commonly referred to as solutions. Solutions have particles which are the size of atoms or molecules - too small to be seen. A solution is a mixture of two or more substances in a single phase. At least two substances must be mixed in order to have a solution. HETEROGENEOUS MIXTURES: The prefix "hetero" indicates different. A heterogeneous mixture consists of visibly different substances or phases of matter. Particle size distinguishes homogeneous solutions from other heterogeneous mixtures.