Objectives Define chemistry List examples of the branches
Objectives • Define chemistry. • List examples of the branches of chemistry. • Compare and contrast basic research, applied research, and technological development.
• Chemistry is the study of a) the composition, structure, and properties of matter b) the processes that matter undergoes c) the energy changes that accompany these processes
Branches of Chemistry • 1. Organic chemistry—the study of most carbon- containing compounds • 2. Inorganic chemistry—the study of nonorganic substances, many of which have organic fragments bonded to metals (organometallics) • 3. Physical chemistry—the study of the properties and changes of matter and their relation to energy
• 4. Analytical chemistry—the identification of the components and composition of materials • 5. Biochemistry—the study of substances and processes occurring in living things • 6. Theoretical chemistry—the use of mathematics and computers to understand the principles behind observed chemical behavior and to design and predict the properties of new compounds
organic chemistry biochemistry inorganic chemistry Chemistry physical chemistry analytical chemistry
Objectives 1. Identify the characteristics of matter and substances 2. Differentiate among the three states of matter 3. Define physical property and list common physical properties of substances
Matter • Has mass and takes up space • Everything is made of matter • Mass – the amount of matter an object contains • Golf ball has greater mass than tabletennis ball
Properties and Changes in Matter Every substance has characteristic properties. Properties are either Extensive or Intensive Extensive Properties: depend on the amount of matter present Examples: mass, volume, amount of energy Intensive Properties: do not depend on the amount of matter present Examples: melting point, boiling point, density
• Matter that has a uniform and definite composition is called a substance. All substances are pure. All samples of a substance have identical physical properties. Example: sucrose • Physical properties – quality or condition of a substance that can be observed or measured without changing its composition
Change of State: Physical change of substance from one state to another Solid: matter in this state has a definite volume and shape. Liquid: matter in this state has definite volume but indefinite shape. Gas: matter in this state has neither definite volume or shape.
An important 4 th state of matter is something called Plasma: high temperature physical state of matter in which atoms lose most of their electrons
Properties of Matter Property Solid Liquid Shape definite indefinite Gas or Vapor indefinite Volume definite indefinite Expansion on heating very slight moderate great almost incomp readily compress Compressibility almost incomp
Gas vs. Vapor • Gas - form of matter that takes both the shape and volume of its container, easily compressible Those substances that exist in gaseous state at ordinary room temperature • Vapor – gaseous state of a substance that is generally a liquid or solid at room temperature (steam)
Physical Properties • Color • Solubility • Odor • Hardness • Melting point • Boiling point • Density – ratio of the mass of an object to its volume
Physical Changes • • • Does not alter chemical composition Boil Freeze Dissolve Melt Condense Break Split Crack Grind Crush Bend
Example of Physical Change • Sodium chloride (table salt) • Solid at room temperature • Can melt to form a liquid • Can boil to form a vapor
Change of Phase: When a substance goes from one form to another, (almost) always in the same order solid liquid gas HEAT - HEAT
Change of Phase (for water): melting/freezing point boiling/condensation point 0ºC solid (ice) MELTING FREEZING 100ºC liquid (water) BOILING CONDENSING gas (steam)
Objectives 1. Categorize a sample of matter as a substance or mixture 2. Distinguish between homogeneous and heterogeneous samples of matter
Words to Know • Mixture – a physical blend of two or more • substances; compositions may vary (salad, blood) Heterogeneous mixture – not uniform in composition (spaghetti sauce, Lucky Charms cereal, granite rock, paint, soup, concrete) • Homogeneous mixture (solutions) – uniform in composition (glass, salt water, a silver ring, air, tap water)
Objectives • Explain the difference between an element and a compound • Identify the chemical symbols of common elements • Name the common elements, given their symbols
Elements and Compounds • Elements and compounds are substances • Elements - Simplest forms of matter that can exist under normal lab conditions - Cannot be separated into simpler substances - Building blocks for all other substances - Examples: oxygen, carbon, hydrogen
• Compounds – chemical combination of two or more elements - Can be separated into simpler substances - Example: Sucrose is C 12 H 22 O 11 Heating sucrose - turns light brown and then black, breaking down completely into carbon and water vapor Water is a compound – electricity will break it down into hydrogen and oxygen gases
• In general, the properties of compounds are quite different from those of their component elements Example: Sodium Chloride (Na. Cl) is common table salt Sodium (Na) is a soft metal that reacts vigorously with oxygen and water (stored under oil). It is used in street lamps. Chlorine (Cl) is a pale yellow-green poisonous gas used to disinfect water.
Summary Matter Substance Element Compound Mixture of Substances Homogeneous Mixture Heterogeneous Mixture
Examples • Substances – oxygen, neon, iron, water, sodium chloride, sucrose, carbon dioxide, citric acid, copper, gold • Mixtures – apple, sand, air, paint, granite, laundry detergent, cereal, salad dressing, salt water
Symbols and Formulas • • • There are more than 100 known elements 90 Elements are found in nature All elements beyond #92 (uranium) on the periodic table are laboratory-made and radioactive Technetium (#43) and promethium (#61), although less complex than uranium, are not found in nature Each element is represented by a one or two letter symbol, usually based on its name
• The first letter of a chemical symbol is always • • • capitalized If a second letter is used, it is lowercase Some symbols are derived from Latin or Greek names Subscripts in compounds represent the proportions of the various elements in the compound Example: H 2 O – Two atoms of hydrogen to every atom of oxygen Note: The number 1 is not written, it is understood
Examples: • O 2 - oxygen • C - carbon • Na – natrium (Sodium) • K – kalium (Potassium) • Fe – ferrum (Iron) • Sucrose: C 12 H 22 O 11
Objectives • Differentiate between physical and chemical changes in matter • Apply the law of conservation of mass
Words to Know • Chemical reaction – one or more substances • • • change into new substances [iron and oxygen form iron oxide (rust)] Reactants - starting substances (iron and oxygen) Products – substances formed (iron oxide : rust) Chemical property – ability of a substance to undergo a chemical reaction and to form any new substance Rusting is a chemical property of iron
Chemical Properties and Chemical Changes Chemical Property: a substances ability to undergo changes that transform it into different substances. Examples: Rusting material(after) Iron + Oxygen (g) Iron oxide (rust) (before)
Chemical Properties and Chemical Changes Chemical Change: a change in which one or more substances are converted into different substances. Reactants Products Reactants: the substances that react in a chemical change Products: the substances that are formed in a chemical change. Carbon + Oxygen Carbon dioxide
Chemical Change • Heat, light, and change in color or odor • Formation of a gas or a solid from liquid • Burn • Rot • Rust • Decompose • Ferment (Production of ethanol from sugars by • • • the action of yeast or bacteria) Explode Corrode Usually irreversible
Examples of Chemical Change • Fizz of antacid tablet dropped into water, exploding fireworks, autumn colors • Zinc metal reacts with sulfuric acid to release hydrogen gas • A red solid of silver chromate forms when a yellow solution of sodium chromate is added to a colorless solution of silver nitrate
Writing Chemical Equations • Arrows – “changes into” or “produce” • Reactants on left side of arrow • Products on right side of arrow • Hydrogen + Oxygen Water
Chemical Reactions and Energy • Energy is always absorbed or given off in a chemical reaction • Cooking food – energy is absorbed • Burning natural gas – energy is given off • An energy change in itself is not proof that a chemical reaction took place (Think of boiling water. Boiling is a physical change. )
Conservation of Mass • In any physical change or chemical reaction, • • mass is neither created nor destroyed In every case, the mass of the products is equal to the mass of the reactants Combustion (burning) of coal: Atmospheric oxygen combines with the coal and produces carbon dioxide gas, water vapor, and a small ash residue
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