chem chapter 1 part 1
DESCRIPTION
CHEM PART 1TRANSCRIPT
Chapter One Matter and Life
Chem100: General & Consumer Chemistry
Natural Sciences Department College of Science & Information Technology
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1.1 Chemistry: The Central Science Chemistry is often referred to as “The Central Science” because it is crucial to all other sciences.
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The Study of Change
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Present Definition
It is the study of matter – its composition,
structure, properties, the changes its undergoes and the energy that accompanies the changes.
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u Matter: Anything that has mass and occupies space – things you can see, touch, taste, or smell.
u Property: a characteristic that can be used to describe a substance. Size, color, temperature are most familiar properties of matter. Less familiar properties include: Chemical composition: what matter is made of. Chemical Reactivity: how matter behaves.
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u Physical Change: Does not alter the chemical makeup of a substance. Change is reversible. Melting of solid ice is a physical change. In this case only change in form takes place and the change is reversible. u Chemical Change: Alters chemical makeup of a substance. Change is irreversible. Rusting of iron is a chemical change. Here, iron combines with oxygen and produces a new substance rust. u Nuclear Change: Yields new element(s) not present before the reaction.
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4Fe(s) + 3O2(g) ⎯→ 2Fe2O3 (s) 2H(g) + 2H (g) ⎯→ 4He↑
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1.2 States of Matter Matter exist in three forms: solid, liquid, and gas. Solid: A substance that has a definite shape and volume. Liquid: A substance that has a definite volume but that changes shape to fill the container. Gas: A substance that has neither a definite volume nor a definite shape. Many substances, such as water, can exist in all three states depending on the temperature. The conversion of a substance from one state into another is known as change of state.
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The three states - the solid state, the liquid state, and the gaseous state - of water are shown in Figure 1.3 below.
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1.3 Classification of Matter
u Pure Substance: Uniform in its chemical composition and properties. Sugar and water are pure substances. u Mixture: Composition and properties may vary. Different amounts of sugar dissolved in water will determine sweetness of water. Sugar water is an example of a mixture.
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u Chemical Compounds: Substance that can be broken down into simpler substances. Water is a chemical compound since it can be broken down into hydrogen and oxygen by passing electric current through it.
u Element: Substance that can not be broken down chemically into simpler substances. Hydrogen, oxygen, nitrogen are example of elements.
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The classification of matter is summarized in Fig 1.4 below.
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1.4 An Example of a Chemical Reaction
When the element nickel, a solid metal, is mixed with a colorless solution of hydrochloric acid in a test tube, the nickel is slowly eaten away, the colorless solution turns green, and a colorless gas bubbles out of the test tube.
Ni(s) + HCl(aq) ⎯→ NiCl2(aq) + H2↑
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1.5 Chemical Elements and Symbols
115 Elements are known until today. Only 90 of these elements occur naturally, remaining are produced artificially by chemists and physicist. u Some familiar elements are iron, tin,
carbon, oxygen, hydrogen, sulfur, etc. u Some unfamiliar elements are niobium,
rhodium, thulium, californium etc.
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Each element has its own unique symbol. – One or two letter symbols are used to
represent elements. – First letter is always capitalized and the
second letter is always a lower case. – Some symbols came from elements modern
name such as ‘H’ for hydrogen, ‘O’ for oxygen, ‘N’ for nitrogen, etc.
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u A few symbols for elements are derived from their Latin names. For example, ‘Na’ for sodium came from its Latin name Natrium.
u All naturally occurring elements are not equally abundant. Oxygen and silicon together constitute 75% of the earth’s crust.
u Chemical Formula: A notation for chemical compound using element symbols and subscripts to show how many atoms of each element are present.
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The formula for water is H2O. H2O indicates that two hydrogen and one oxygen combined together to produce water. When no subscript is given for an element a subscript of ‘1’ is understood.
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1.6 Elements and the Periodic Table Periodic Table, shown below, is a representation of 113 elements in a tabular format.
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Large amounts of information regarding the properties of elements is embedded in periodic table. Elements are roughly divided into 3 groups
q Metals q Nonmetals q Metalloids
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Metals, nonmetals, and metalloids appear in distinct places on the periodic table
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Metals: 89 of the 115 elements are metals. They appear on the left side of the Periodic Table. Some common properties of metals are:
q Solid at room temperature (except mercury which is a liquid)
q Good conductor of heat q Good conductor of electricity q Malleable q Ductile
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Nonmetals: Appear on the right side of the Periodic Table. 17 elements are nonmetals. Nonmetals are poor conductors of heat and electricity. Out of these 17 nonmetal elements
– Four are gases at room temperature (H, N, O, etc.)
– Five are solids (sulfur) – One is a liquid (bromine).
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Metalloids: Appear between metals on the left side and nonmetals on the right side on the periodic table. Their properties are between metals and nonmetals. Boron, silicon, arsenic are examples of some of the metalloids.
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A Science for the 21st Century
Health and Medicine Breakthroughs of the Recent Century: 1. Health and Sanitation Systems 2. Surgery with Anesthesia 3. Development of Antibiotics and Vaccines 4. Gene Therapy* (still in experimental stage)
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A Science for the 21st Century
Energy and Environment Fact: Fossil Fuels (Coal, Oil and Natural Gas)
are in decline (estimates: 50-100 years) Solution: Turn to Alternative Forms of Energy 1. Solar Energy 2. Nuclear Power 3. Wind Power
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A Science for the 21st Century
Materials Science Materials Developed in the Past: 1. Plastics 2. Metal Alloys Materials Being Developed: 1. Room Temperature Superconductors 2. Fiber Optics
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A Science for the 21st Century
Food and Agriculture Common Agricultural Chemicals Used:
fertilizers, pesticides, herbicides A question of alternatives? Common Food Additives/Preservatives: 1. In Meat Products – sodium nitrate/nitrite 2. In Beverages – High-Fructose Corn Syrup
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Chapter Summary
u Chemistry is the study of matter. u Matter is anything that has mass and
occupies space. u Physical change does not alter the chemical
makeup of a substance. Change is reversible. u Chemical change alters chemical makeup of
a substance. Change is irreversible. u Pure substances have uniform chemical
composition and properties.
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Chapter Summary Contd.
u Composition and properties of a mixture may vary.
u Substance that can be broken down into simpler substances is a chemical compound.
u Substance that can not be broken down chemically into simpler substances is known as an element.
u Elements are represented by one or two letter symbols. First letter is always capitalized and the second letter is always a lower case.
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Chapter Summary Contd.
u Chemical Formula is a notation for chemical compound to show how many atoms of each element are present. u Periodic Table is a representation of 115 elements in a tabular format. u Elements are roughly divided into 3 groups
– Metals – Nonmetals – Metalloids
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A 21st Century Science
u Health and Medicine u Energy and Environment u Materials Science u Food and Agriculture
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End of Chapter 1 Part I
Chapter One