Introduction to General Chemistry Ch Lecture 1 Suggested HW: 5, 7, 8, 11, 13, 15, 16, 27

What is Chemistry? Chemistry is the study of properties of substances and how they react Chemical substances are composed of matter – Matter is the physical material of the universe; anything with mass that occupies space is matter – Matter can take numerous forms – Most matter is formed by unique arrangements of elementary substances called elements

Elements, Compounds, and Molecules An element can easily be defined as a substance that can not be broken down into simpler substances Millions of different materials in the world, all comprised of some combination of only 118 elements – Similar to how the alphabet combines 26 letters to yield hundreds of thousands of words, elements bond in unique arrangements to give different molecules – Molecules agglomerate to yield compounds

H O O H H O H Molecules Are Comprised of Uniquely Arranged Atoms. Different Molecules Have Different Properties.

ethanol acetic acid acetaldehyde (hangover) carbon dioxide methanol BLINDNESS!!! Small Molecular Differences Can Yield Vastly Different in Terms of Biological Interactions

Relief of Morning Sickness Severe Limb Defects Small Molecular Differences Can Yield Vastly Different in Terms of Biological Interactions

C 6 H 12 O 6 Technically, glucose and fructose are the same. So is high fructose corn syrup really that bad for you??? Small Molecular Differences Can Yield Vastly Different in Terms of Biological Interactions

Small Molecular Differences Can Yield Vastly Different in Terms of Biological Interactions

Na (sodium metal)Cl 2 (chlorine gas) Na + Cl - The Properties of Molecules Differ Vastly from those of the Atoms That Comprise Them

Different atomic arrangements can change physical properties Carbon (graphite vs diamond)

Spatial Dimensions of Compounds Can Alter Properties 5 nm 50 nm Bulk Gold Gold Nanoparticles

Spatial Dimensions of Compounds Can Alter Properties CdSe quantum dots 2 nm12 nm

Solids Atoms tightly bound Fixed volume and shape (does not conform to container) A chemical is denoted as solid by labeling it with (s) Phases of Matter: Solids, Liquids and Gases S(s)

Liquids Atoms less tightly bound than solids Has a definite volume, but not definite shape (assumes the shape of its container) Denoted by (L) Phases of Matter: Solids, Liquids and Gases H 2 O (L)

Gases Free atoms No shape, no definite volume Can be expanded or compressed (like engine piston) Denoted by (g) ; ex. O 2 (g) Phases of Matter: Solids, Liquids and Gases

In chemistry, the scientific method is used to investigate scientific phenomena & acquire new knowledge Empirical evidence is gathered which supports or refutes a hypothesis Empirical evidence is either quantitative or qualitative – Quantitative data is numerical, and results can be measured – Qualitative data is NOT numerical, but consists of observations and descriptions Qualitative and Quantitative Analysis

Quantitative data How much C is formed? How efficient is the reaction? What is the rate of the reaction? Qualitative data What color is it? Is it solid, liquid, gas? How does it smell? A + B C Quantitative and Qualitative Analysis

Quantitative measurements are represented by a: NUMBER and a UNIT A unit is a standard against which a physical quantity is compared physical quantity – Temperature is measured in C o, K o,or F o – Currency is measured in $USD – Distance is measured in meters, miles, ft, etc. – Time is reported in seconds, minutes, hr, etc. Internationally accepted system of measurements is called the SI unit system Units

SI Unit System: The Units of Physical Science

Prefixes indicate powers of 10 – ex. k= 10 3 ; 5 kg = 5 x (10 3 )g Greek Prefixes

Important: All integers end with a decimal point, even though it is not commonly written (1  1. ) If no factor is shown, assume there is a 1. in front of powers of 10: 10 2 = 1. x = 1. x For every positive power of 10, shift the decimal 1 place to the right, add a zero for each place 10 2 = 1. x 10 2 = = 1. x 10 5 = Scientific notation indicates a factor (F) multiplied by a power (n) of 10 F x 10 n (1 < F < 10) A Review of Scientific Notation

For all non integers, simply shift the decimal. 2.5 x 10 5 = x 10 8 = For negative exponents, shift the decimal left. All values less than 1 have negative exponents x = x = Convert to standard notation x x x 10 0 Convert to scientific notation A Review of Scientific Notation

When multiplying powers of 10, the product is the sum of the powers – 10 2 x 10 5 = = 10 7 – (2.5 x 10 3 ) x (4 x ) = (2.5 x 4) x (10 3+(-6) ) = 10 x = 1.0 x When dividing powers of 10, subtract – 10 2 / 10 5 = 10 (2-5) = – (6.6 x ) / (2.2 x ) = 3.0 x (10 10-(-6) ) = 3.0 x Multiplying and Dividing Exponents (Review)

Convert the following values to grams in proper scientific notation. – kg – mg – 481 µg Group Work

Why Are Units Important? Example #1 In 1999, NASA lost the $125M Mars Orbiter System. One group of engineers failed to communicate with another that their calculated values were in English units (feet, inches, pounds), and not SI units. The satellite, which was intended to monitor weather patterns on Mars, descended too far into the atmosphere and melted.

Why Are Units Important? Example #2 In 1983, an Air Canada Plane ran out of fuel half way through its scheduled flight. Why? Airline workers improperly converted between liters and gallons. Luckily, no one died.

Why Are Units Important? Example #3 A case was reported in which a nurse administered 0.5 g of a sedative to a patient. The patient died soon after The patient should have only received 0.5 grains (≈ g) but the units were not listed. That was the equivalent of 8 doses!!

Many measured properties have units that are combinations of the fundamental SI units Volume: defines the quantity of space an object occupies; or the capacity of fluid a container can hold – expressed in units of (length) 3 or Liters (L) – 1 L is equal to the volume of fluid that a cube which is 10 cm on each side can hold 10 cm V = (10 cm) 3 = 1000 cm mL = 1000 cm 3 1 L = 1000 cm 3 mL = cm 3 Derived SI Units: VOLUME

All matter has mass, and must therefore occupy space. Density correlates the mass of a substance to the volume of space it occupies. Density = mass per unit volume (mass/volume). Different materials have different densities. Derived SI Units: DENSITY Would a 20-gallon container filled with bricks have the same mass as an equivalent volume of feathers? NO!

A cubic container that is 25 cm on each side is filled with ethanol. The density of ethanol is 0.79 g/mL. – What is the volume of ethanol in the cube in mL? – What is the volume in L? – What is the mass of ethanol in kg? Give answers in scientific notation!! Group Work

Derived SI Units: ENERGY What is Energy? – Energy is defined as the capacity to perform “work” How do we define work? Work is defined as the action of applying a force acting over some distance. Work can not be done if no energy is available. In SI units, we use the unit Joule (J) to represent energy.

Energy is never created or destroyed, merely converted between forms and transferred from place to place. The total energy of the universe is finite. Conservation of Energy

Energy comes in many forms and can be converted from one form to another. Some examples are given: Chemical Energy – Energy stored in chemical bonds (e.g. gasoline, coal, etc.) that can be released by chemical reaction, typically combustion (fire) Heat Energy (thermal energy) – Heat is defined as energy flow between bodies of matter resulting from collisions of molecules or random motions of electrons. Forms of Energy

Mass Energy – Energy and mass are interchangeable. During a fusion reaction (e.g. stars), mass is lost and energy is formed. This mass appears as energy according to the following: where m is the change in mass (in kg), c is the speed of light, and E is the energy released (J). This is the basis of nuclear power. Kinetic Energy – Energy of motion (e.g. a moving car). An object with mass m, moving at a velocity V (meters/sec) has kinetic energy: Forms of Energy

Potential Energy – Potential energy corresponds to energy that is stored as a result of the position of mass in a field. If a mass m is held at a height h (meters) above the ground, assuming a gravitational acceleration of 9.8 m/s 2 (g), its potential energy is: – If the object is dropped, it loses potential energy. However, it speeds up as it falls, so its kinetic energy increases equally (conversion). Forms of Energy

Electrical Energy – Energy resulting from electric current, the movement of electrons through a conductive circuit. Electrical energy is a type of potential energy. For a charge q (coulombs, C) moving across a voltage, V Light/Radiation – The energy of a wave of light is calculated as the product of Planck’s constant, h (J s), and the wave frequency, ν (1/s) Forms of Energy

It is often necessary to express the rate of energy usage. This is called power. Typically, we speak in terms of energy per second. In SI units, a joule per second (J/s) is known as a watt (W). Power

Temperature: a measure of the tendency of a substance to lose or absorb heat. Temperature and heat are not the same. Heat always flows from bodies of higher temperature to those of lower temperature – The stove top is ‘hot’ because the surface is at a much higher temperature than your hand, so heat flows rapidly from the stove to your hand – Ice feels ‘cold’ because it is at a lower temperature than your body, so heat flows from your body to the ice, causing it to melt Temperature

When performing calculations in chemistry, temperature must always be converted to Kelvin ( o K) units (unless otherwise stated). The lowest possible temperature that can ever be reached is 0 o K, or absolute zero. At this temperature, all molecular motion stops. To convert temperatures to the Kelvin scale: o K : o C Temperature