- Slides: 24
Matter, Properties & Changes CVHS Chapter 3
Chemical Properties • The ability of a substance to combine with or change into one or more other substances is called a chemical property – – Fe rusting Fe doesn’t react w/ N 2(g) CH 2 O burning Inability of a substance to change into another
Properties & States of Matter • Every substance has its own unique set of chemical & physical properties • Environment affects how matter reacts – Temperature – Pressure • States (Physical property of a substance) – – Solid Liquid Gas Plasma (only on earth in lightning bolts)
Solids • Has its own definite shape and volume • Tightly packed – Expands slightly when heated – May not conform to shape of container b/c tightly packed
Liquids • Flows • Constant Volume • Takes shape of its container • Particles of liquid – Loosely packed – Not held in place – Able to slide past each other – b/c of way they are packed, virtually incompressible – Expand when heated
Gases • Flows to conform to shape of container • Fills entire container • Particles very far apart – Compressible b/c of space between particles • Gas: @ room temp. • Vapor: liquid or solid at Room Temp. – Steam is a vapor b/c water is a liquid @ room temp.
Physical Changes • A substance often undergoes changes that result in a dramatically different appearance yet leave the composition of the substance unchanged. • An example is the crumpling of a sheet of aluminum foil or boiling a container of water.
Chemical Changes • Chemical properties relate to the ability of a substance to combine with or change into one or more substances. • A process that involves one or more substances changing into new substances is called a chemical change, which is commonly referred to as a chemical reaction. • New substance formed has diff. composition & properties than the original substances • Iron reacts w/ Oxygen to form rust
Chemical Changes • Thus iron and oxygen are reactants and rust is a product. • When you encounter terms such as explode, rust, oxidize, corrode, tarnish, • The silver earring is ferment, burn, or rot, the oxidized: meaning generally refers to – Electrons are removed a chemical reaction in from the silver earring by which reactant substances sulfur in the air forming silver (II) sulfide produce different product – 2 Ag + S Ag 2 S substances
Conservation of Mass • Total mass of material before and after a chemical reaction is the same • Scientists observed so often they called it THE LAW OF CONSERATION OF MASS
Practice Questions • Identify each of the following as a property of a solid, liquid, or gas. Some answers will include more that one state of matter. • flows and takes the shape of a container – Gas & Liquid • Compressible – Gas • made of particles held in a specific arrangement – Solid • has definite volume – Solid & Liquid • always occupies the entire space of its container – Gas • has a definite volume but flows – Liquid
More Practice! • Identify each of the following as an example of a chemical change or a physical change. A. Moisture in the air forms beads of water on a cold windowpane A. Physical B. An electric current changes water into hydrogen and oxygen. B. Chemical C. Yeast cells in bread dough make carbon dioxide an ethanol from sugar. C. Chemical
Still More Practice • A reaction between sodium hydroxide and hydrogen chloride gas produces sodium chloride and water. A reaction of 22. 85 g of sodium hydroxide with 20. 82 g of hydrogen chloride gives off 10. 29 g of water. What mass of sodium chloride is formed in the reaction? • 33. 38 g sodium chloride
Elements • Pure substance, can’t be separated by physical or chemical methods • All matter can be broken down into elements • Each element has unique symbol & name – The chemical symbol consists of one, two, or three letters; the first letter is always capitalized and the remaining letter(s) are always lowercase.
Periodic Table • As more elements were discovered over time, a need for organization became evident • 1869: Mendeleev organized elements into columns & rows based on similarities & mass (had some errors) • Current Periodic table – Organized by atomic # (protons) – Horizontal Rows: periods – Vertical Columns: groups or families • Families have similar properties The table is called “periodic” because the pattern of similar properties repeats as you move from period to period.
Compounds • Pure substance • A combination of two or more different elements that are combined chemically – Water, table salt, sugar, aspirin – table salt, or sodium chloride, is composed of one part sodium (Na) and one part chlorine (Cl), and its chemical formula is Na. Cl – Water is composed of two parts hydrogen (H) to one part oxygen (O), and its formula is H 2 O • Can be broken down into simpler substances by chemical reactions
Compounds • Can be broken down into simpler substances by a chemical reaction • Compounds are usually more stable than their individual component elements • Compounds have different properties than their constituent elements – H 2 & O 2 are gases – H 2 O is a liquid • Separation requires external energy – Heat – electricity
Law of Definite Proportions • A compound is always composed of the same elements in a definite proportion by mass • Mass of compound = the sum of the masses that make up the compound • The ratio of the mass of an element to the mass of the compound is:
% Composition Practice • A 2. 89 -g sample of sulfur reacts with 5. 72 g of copper to form a black compound. What is the percentage composition of the compound? • 33. 6% sulfur, 66. 4% copper • A 134. 50 -g sample of aspirin is made up of 6. 03 g of hydrogen, 80. 70 g of carbon, and 47. 77 g of oxygen. What is the percent by mass of each element in aspirin? • 4. 48% hydrogen, 60% carbon, 35. 52% oxygen
Law of Multiple Proportions • The law of multiple proportions states that when different compounds are formed by a combination of the same elements, different masses of one element combine with the same relative mass of the other element in a ratio of small whole numbers. • ratios express the relationship of elements in a compound
Law of Multiple Proportions • Hydrogen Peroxide (H 2 O 2) & Water (H 2 O) • Each compound contains the same elements (hydrogen and oxygen). • Hydrogen peroxide differs from water in that it has twice as much oxygen • When we compare the mass of oxygen in hydrogen peroxide to the mass of oxygen in water, we get the ratio 2: 1 H 2 O 2 H 2 O
Yipeeeee! More Practice • Identify each of the following as an example of a homogeneous mixture or a heterogeneous mixture. • 70% isopropyl rubbing alcohol – homogeneous • a pile of rusty iron filings – heterogeneous • Concrete – heterogeneous • Saltwater – homogeneous • Gasoline – homogeneous • Bread – heterogeneous
I’m so excited, even more practice! • Identify each of the following as an example of an element or a compound. • Sucrose (table sugar) C 12 H 22 O 11 – compound • The Helium (He) in a balloon – Element • Baking Soda (Na. HCO 3) – Compound • A Diamond (C) – Element