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MATTER
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Chemistry is the study of the composition and behavior of matter.
Introduction Chemistry is the study of the composition and behavior of matter.
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Matter is anything with mass and volume
book air smoke
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LAW OF CONSERVATION OF MATTER
Matter cannot be created or destroyed, it can only be changed from one form to another.
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Mass is a measure of the amount of material within an object.
***Mass is independent of gravity; weight is not!
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LAW OF CONSERVATION OF MASS
Mass cannot be created or destroyed, it can only be changed from one form to another.
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10 g reactants → 10 grams products
20 mlc reactants → 20 mlc products ***The Law of Conservation of Mass tells us that what we start with must EQUAL what we end up with!
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Volume is the amount of space occupied by an object
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Physical States of Matter
Solid definite shape and definite volume
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Liquid definite volume, takes shape of container (indefinite shape)
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Gas takes volume and shape of container
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Plasma Gas particles that have broken apart to become positive ions & stream of electrons
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Physical vs Chemical Changes
1. In physical changes, the identity of a substance remains the same. Example: liquid water is heated to form water vapor H2O (l) → H2O (g)
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2. In chemical changes, the identities of substances change and new substances form.
Example: Mercury (II) oxide → mercury + oxygen 2HgO → 2Hg + O2
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Evidence of Chemical Change
Formation of a gas (bubbles) Evolution of heat and/or light Formation of a precipitate
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Solution A + Solution B → solid + solution C
Precipitate: A solid produced in a chemical reaction between solutions Solid “falls out” of solution Solution A + Solution B → solid + solution C [two homogeneous mixtures] [heterogeneous mixture]
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A change in color is not a reliable indicator of a chemical change.
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In chemical equations, the reactants are on the left side of the arrow, and the products are on the right side of the arrow. Reactants → Products
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Examples: 2Na + Cl2 → 2NaCl Reactants → Products 2H2 + O2 → 2H2O
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Properties of Matter Chemical properties can only be identified by trying to cause a chemical change. Examples include reactivity with oxygen (rusting of iron), flammability
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Physical properties can be determined without changing the nature of the substance.
Examples include color, state, texture, melting point, boiling point, density
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Two types of physical properties:
Intensive Physical Properties- depend only on the identity of the substance Examples: density, boiling point, melting point
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2. Extensive Physical Properties
depend on the amount of substance present Examples: volume, mass, length, width
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Classification of Matter
All matter is classified as a PURE SUBSTANCE or a MIXTURE.
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1. Pure substances include elements and compounds.
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A. Elements: All matter is composed of elements
Fundamental unit of matter Composed of one kind of atom Cannot be broken down by ordinary chemical means
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-Currently more than 114 identified
Each has specific properties and characteristics Each has a unique symbol
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First is capitalized, second is not
Chemical Symbols: One or two letters First is capitalized, second is not often first letter or first two letters of the name Carbon C Calcium Ca Boron B Bromine Br
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Some symbols are derived from their Latin names:
Iron Fe (Ferrum) Sodium Na (Natrium) Silver Ag (Argentum)
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B. Compounds The chemical combination of two or more elements Has a formula Can be broken down by ordinary means into elements
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H2O is a compound made up of the elements hydrogen and oxygen
NaCl is a compound made up of the elements sodium and chlorine
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Examples of Pure Substances:
pure water (compound): H2O not tap water carbon (element):C sodium chloride (compound):NaCl
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Sodium chloride (table salt)
Each pure substance has unique properties allowing us to recognize and distinguish one from another. Sodium Chlorine Sodium chloride (table salt) soft, silvery metal reacts violently with water pale greenish yellow gas poisonous colorless crystals relatively non-toxic dissolves easily in water
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2. Mixtures: Each part of a mixture retains its original properties Most matter = mixtures
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All mixtures can be separated into their original parts by using physical changes/properties.
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Two types of mixtures: 1. Homogeneous- Composition uniform throughout Homogeneous mixtures are also called SOLUTIONS All pure substances are homogeneous.
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EXAMPLES: salt water sugar water air
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2. Heterogeneous Composition varies in properties and appearance throughout Most mixtures are heterogeneous
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EXAMPLES: sand in water salt and sugar tap water concrete
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MATTER Pure Substances Mixtures
Homogeneous Mixtures Heterogeneous Mixtures Compounds Elements
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Energy is the ability to do work
ENERGY OF MATTER Energy is the ability to do work
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Every change in matter involves a change in energy.
Endothermic processes absorb energy Exothermic processes release energy
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Law of Conservation of Energy:
Energy cannot be created or destroyed, it can only be changed from one form to another.
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Heat is the energy transferred between objects that are at different temperatures.
Temperature is a measure of the average kinetic energy of the particles in an object
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Stop and do today’s homework
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