Unit 1-7 pure matter and energy Do now: find in the textbook the difference between atom, element, molecule and compound
The Particulate Nature of Matter • Matter has mass and occupies space. • It is composed of tiny particles called atoms (undividable).
Elements • Pure elements contain only one type of atom – elemental copper contains only copper atoms and elemental gold contains only gold atoms.
Molecules and Compounds • Molecules are particles that contain two or more atoms. • Compounds are particles that contain two or more different types of atoms.
Terms • Matter- anything that has mass and volume • Atom- smallest unit of an element that keeps the properties of element • Element- pure substance made of only one type of atom …. think of an element as being a group of the same type of atoms … the plural of atom • Molecule- formed from two or more atoms held together with chemical bonds (ionic, covalent) • Compound- a group of two or more different types of atoms … again, think of it as being the plural of molecule
The States of Matter (pure) • Pure matter exists in three states: • Solid: a rigid substance with a definite shape and volume • Liquid: has a definite volume but takes the shape of its container (indefinite shape) • Gas: takes the shape and volume of its container
States of Matter • Solids • particles vibrate but can’t move around • fixed shape • fixed volume • Virtually incompressible
States of Matter • Liquids • particles can move around but are still close together • variable shape • fixed volume • Virtually incompressible
States of Matter • Gases • particles can separate and move throughout container • variable shape • variable volume • Easily compressed • Vapor = • gaseous state of a substance that is a liquid or solid at room temperature
States of Matter Definite Volume? Definite Shape? Temp. increase Com-pressible? Slight Expansion Solid YES YES NO Slight Expansion Liquid NO NO YES Large Expansion Gas NO NO YES
Energy Changes in Matter • When any change occurs, energy is always involved • Where is the energy? …. in the bonds • To break bonds, energy is added • When bonds reform, energy is given off • Where does the energy come from or go to? System vs. Surroundings • Energy is never destroyed or created (law of conservation of energy)
Law of conservation Law of Conservation of Energy • Energy can be neither created or destroyed in ordinary changes (not nuclear), it can only change form. Law of conservation of mass • The matter cannot be destroyed or created. • Mass before chemical change = mass after chemical change • They are not just good ideas … they’re the laws.
Two major types of energy • Potential- stored energy; energy due to position • Kinetic Energy- energy something has because its moving
Types of Energy based on sources • Heat- the energy that moves because of a temperature difference. • Chemical energy- energy released or absorbed in a chemical change found in the chemical bonds. • Electrical energy - energy of moving charges • Radiant Energy- energy that can travel through empty space (light, UV, infrared, radio) • Nuclear Energy – Energy from changing the nucleus of atoms • All types of energy can be converted into others.
Homework • Handout page 1, due tomorrow
Properties & Changes in Matter Do now: define extensive vs. intensive properties, physical vs. chemical properties
Physical Properties • Physical Property • can be observed without changing the identity of the substance
Physical Properties • Physical properties can be described as one of 2 types: • Extensive Property • depends on the amount of matter present (example: length) • Intensive Property • depends on the identity of substance, not the amount (example: scent)
Extensive vs. Intensive • Examples: • boiling point • volume • mass • density • conductivity intensive extensive extensive intensive intensive
Chemical Properties • Chemical Property • describes the ability of a substance to undergo changes in identity
Physical vs. Chemical Properties • Examples: • melting point • flammable • density • magnetic • Tarnishes/rust in air physical chemical physical physical chemical
Physical vs.. chemical changes • Physical Change • changes the form of a substance without changing its identity • properties remain the same • Examples: cutting a sheet of paper, breaking a crystal, all phase changes
Evaporation = Condensation = Melting = Freezing = Sublimation = Liquid -> Gas Gas -> Liquid Solid -> Liquid Liquid -> Solid Solid -> Gas Phase Changes examples
Chemical Changes • Process that involves one or more substances changing into a new substance • Commonly referred to as a chemical reaction • New substances have different compositions and properties from original substances
Chemical Changes • Signs of a Chemical Change • change in color or odor • formation of a gas • formation of a precipitate (solid) • change in light or heat
Physical vs. Chemical Changes • Examples: • rusting iron • dissolving in water • burning a log • melting ice • grinding spices chemical physical chemical physical physical
What Type of Change?
Homework • Handout page 2, due tomorrow