atomic theory 原子论

Order Particles fixed in position
Gas
Liquid
Solid
• Solids, Liquids, and Gases
– Gases have no defined shape or defined volume
• LoFra Baidu bibliotek density
– Liquids flow and can be poured from one container to another
• The phlogiston theory. (A) In this theory, burning was considered to be the escape of phlogiston into the air. (B) Smelting combined phlogiston-poor ore with phlogiston from a fire to make a metal. (C) Metal rusting was considered to be the slow escape of phlogiston from a metal into the air.
• Lavoisier heated a measured amount of mercury to form the red oxide of mercury. He measured the amount of oxygen removed from the jar and the amount of red oxide formed. When the reaction was reversed, he found the original amounts of mercury and oxygen.
Atomic theory
Dalton’s Postulates
1. Every element is composed of tiny particles called atoms 2. All atoms of a given element are identical 1. Atoms of different elements have different properties 3. Atoms of an element are NOT changed into atoms of another element by chemical processes 1. Matter can neither be created nor destroyed 4. Compounds are formed when atoms of more than one element combine
• Discovery of Modern Elements
– Antoine Lavoisier suggested that burning was actually a chemical combination with oxygen. – Lavoisier realized that there needed to be a new concept of elements, compounds, and chemical change. – We now know that there are 89 naturally-occurring elements and at least 23 short-lived and artificially prepared.
– The phlogiston theory viewed phlogiston as a component of all matter. – The burning of a material was considered to be the escaping of phlogiston from the matter. – If a material did not burn, it was considered to contain no phlogiston.
• Sugar (A) is a compound that can be easily decomposed to simpler substances by heating. (B) One of the simpler substances is the black element carbon, which cannot be further decomposed by chemical or physical means.
• A classification scheme for matter.
– A physical change is a change that does not alter the identity of the matter. – A chemical change is a change that does alter the identity of the matter. – A compound is a pure substance that can be decomposed by a chemical change into simpler substances with a fixed mass ratio – An element is a pure substance which cannot be broken down into anything simpler by either physical or chemical means.
Elements and the Periodic Table
• Classification is arranging items into groups or categories according to some criteria. • The act of classifying creates a pattern that helps you recognize and understand the behavior of fish, chemicals, or any matter in your surroundings.
2. The Law of Conservation of Mass:
“The total mass of materials before and after a chemical reaction must be the same. For example, if we combine 89 grams of oxygen with 11 grams of hydrogen under the appropriate conditions, 100 grams of water will be produced—no more and no less.”
• Indefinite shape and takes on the shape of the container.
– Solids have a definite volume
• Have a definite shape.
• Mixtures and Pure Substances
– A mixture has unlike parts and a composition that varies from sample to sample – A heterogeneous mixture has physically distinct parts with different properties. – A homogeneous mixture is the same throughout the sample – Pure substances are substances with a fixed composition
Dalton’s Laws
1. The Law of Constant Composition:
“Any given compound always consists of the same atoms and the same ratio of atoms. For example, water always consists of oxygen and hydrogen atoms, and it is always 89 percent oxygen by mass and 11 percent hydrogen by mass”
• The elements of aluminum, Iron, Oxygen, and Silicon make up about 88 percent of the earth's solid surface. Water on the surface and in the air as clouds and fog is made up of hydrogen and oxygen. The air is 99 percent nitrogen and oxygen. Hydrogen, oxygen, and carbon make up 97 percent of a person. Thus almost everything you see in this picture us made up of just six elements.
EXAMPLE
Isopropyl alcohol is a A. heterogeneous mixture B. homogeneous mixture C. pure substance
D. Compound
E. pure substance and compound
E
• Elements
• Reconsidering the Fire Element
• Here are some of the symbols Dalton used for atoms of elements and molecules of compounds. He probably used a circle for each because, like the ancient Greeks, he thought of atoms as tiny, round hard spheres.
• Priestley produced a gas (oxygen) by using sunlight to heat mercuric oxide kept in a closed container. The oxygen forced some of the mercury out of the jar as it was produced, increasing the volume about five times.
• Classifying Matter
• Matter is usually defined as anything that has mass and occupies space.
Total disorder Lots of empty space
Disorder Some space Particles closer together
• Names of Elements
– The first 103 elements have internationally accepted names, which are derived from:
• The compound or substance in which the element was discovered • An unusual or identifying property of the element • Places, cities, and countries • Famous scientists • Greek mythology • Astronomical objects.