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Chem 121
Introduction to Inorganic Chemistry
What is Matter?• Matter is anything that has mass and occupies
space. • Mass is a measurement of the amount of matter
present. The mass is constant, no matter where it is …on the moon or on earth.
• Weight the a measurement of the gravitational force pulling the object toward earth. The weight of an object will be different on the moon that has a different grav. pull.
Properties and Changes
• Two types of properties:– Physical : Those that can be observed or
measured without changing or trying to change the composition of the matter in question * no original substances are destroyed and no new substances are created. Like Color and SIZE.
– Chemical: properties that matter demonstrates when attmepts are made to change it into other kinds of matter.
Physical Change VS Chemical Change
• Physical Change: Cutting a piece of paper, Boiling water, freezing water, heat is added or removed from matter.
• Chemical Change: burn the paper. ,mix the water with an acid.
A Model of Matter
• Scientific Models are explanations for observed behavior.
• All matter is made up of particles that are too small to see. (molecules)
• Molecules: The smallest particle of a pure substance that has the properties of that substance and is capable of a stable independent existence. A molecule is also the limit of physical subdivision for a pure substance.
Example
• Oxygen: helps a substance burn more rapidly..like wood.– A large amt. or a small amt of Oxygen
would behave the same.– The smallest amt. that would still behave the
same is known as the molecule.
What’s beyond the Molecule?
• John Dalton wanted to know. In 1808 he proposed the following:
• 1. All matter is made up of tiny particles called atoms.
• 2. Substances called elemenats are made up of atoms that are all identical.
• 3. Substances called compounds are comginations of atoms or two or more elements.
Cont.
• 4. Every molecule of a specific compound always contains the same number of atoms of each kind of element found in the compound.
• 5 In chemical reactions, atoms are rearranged, separated, or combined, but are never created nor destroyed.
Types of Molecules
• Diatomic Molecule: contains two atoms• Homoatomic molecule: contain only one kind
of atom.• Heteratomic molecule: contain more then one
kind of atom• Triatomic molecule: 3 non-identical atoms• Polyatomic molecule: more then 3
Classification of Matter
• Pure Substances - not adulterated or mixed with anything else.– They have unique and consistent physical and chemical
properties. • Physical Properties: Melting Point Temperature, Color, Density.• Chemical Properties: a chemicals ability to react with other pure
substances. In a chemical reaction, substances lose their identity and form new substances with new chemical and physical properties.
– It undergoes physical change without losing its identity... Eg.( melting, freezing, or evaporation)
Mixtures• Consists of two or more pure substances in varying
proportions. – Heterogeneous – visibly discontinuous..like salt and
pepper.– Homogeneous – have a uniform appearance throughout;
like sugar and water. The mixture is called a solution, and it is described as homogeneous.
• Mixtures can be separated back into their pure substance components.
• Mixtures have properties that are variable and depend on the proportions of the components.
Compounds and Elements
• Compounds: Some pure substances are found to be able to be decomposed into simpler pure substances.
• Elements: pure substances that cannot be further decomposed. It cannot be separated chemically in to simpler substances, nor be created by combining simpler substances.
Measurement and the Metric System
• Measure: - the size, capacity, extent, volume or quantity of anything, especially as determined by comparison with some standard or UNIT.
• Systeme International d’Unite’s.
Significant Figures
• Communicating Degrees of Uncertainty• 4 1 sig fig• 4.0 2 sig figs• 4.000 4 sig figs• 4.0000 5 sig figs
Examples• Do not over represent the amt. of precision that you have.• Which digits are really giving me info about how precise my measurement is?• 0.00700 • If you measure the above in km, it could also be 7.00 m (the previous zeros are
determining the units to use, the trailing zeros determine precision)• 0.052 …(could be re-written as 52 m)• (do not count leading zero’s before the first non-zero digit)• 370. (because they wrote a decimal, it is exactly 370) 3 sig figs.• 10.0 (go to nearest 10th) 3 sig figs• 705.001 ( zero’s are part of measurement ..between non zero digits)• 37,000 (ambiguous) Maybe you measured to the nearest 1000, or nearest 1…you
don’t know. Go with 2 sig figs. (more conservative)• ( A trailing Zero as in 4.130 is significant. (This has 4 sig figs)…
Rules of Thumb
• A trailing zero , 4.130 , is significant.• A zero within a number, 35.06 cm• A zero before a digit as in 0.082 , is not
significant• A number ending in zero with no decimal
point , 20 is ambiguous.
Mulitiplication and Division with Sig Figs
• Let’s say we are calculating the area of a Rectangle 1.69 m x 2.09m
• Area = 3.5321 m2
Use the least precisice number as the basis for the amt. of sig figs.. 3 sig figs..
• Area = 3.53 m2
Another Example
• Calculate how many tiles I need for a room 12.07 ft x 10.1 ft.
• Floor Area = 121.907 ft2
• ** Do not round yet! *** go to the end with all numbers, then establish sig figs and round**
• Tiles in bathroom = 121.907ft2/1.07 ft2
• Tiles = 113.931775701 tiles• 3 sig figs = 114 tiles
Addition and Subtraction• Ex: 1.26 (nearest hundredth , 3 sig figs) + 2.3 (nearest
10th, 2 sig figs) = 3.56• The least precise number went to the 10th, therefore 2
sig figs in result. 3.7
• Or 1.26 + 102.3 = 103.56 (only as precise as the least precise number)…
• 1.26 has 3 sig figs, 102.3 has 4 sig figs, however the least precise measurement is 102.3 as it is measured only to the 10th, not the 100th…therefore the answer will be 4 sig figs, 103.6
Another Example
• One Block: 2.09 m high• Another block: 1.901 m high• How tall is it to stack them?• 1.901 + 2.09 = 3.991• Did I measure the entire stack to the nearst
mm? NO! Only report as precise as the least precise measurement. 3.99m
Another example
• Building: 350 ft tall (ambiguous) • Radio Tower : 8 ft tall• How tall is building plus the tower: 358 ft• We only measured tower to nearest ft.• You have to round to the nearest 10 ft.
Answer is actually 360 ft. or report it as 3.6 x 10 2
Metric System Units
Using Units in Calculationsaka: Dimensional Analysis
• Step 1: Write Down the known or given quantity. Include both numerical value and units of the quantity.
• Step 2: Leave some working space and set the known quantity equal to the units of the unknown quantity.
• Step 3: Multiply the known by one or more factors (conversion factors) to cancel the units of the known and generate the units of the unknown.
• Step 4: Do the arithmetic .
Example Problems
• 50 μL (50 – microliter) sample of blood serum must be expressed as Liters.
• (1μL = 1 x 10-6 L)• Step 1:• Step 2:• Step 3:• Step 4:
Example
• One of the fastest-moving impulses in the body travels at a speed of 400 ft/per second. (ft/s). What is the speed in miles/hr?
Calculating Percentages
Non SI units most common
Prefixes for Metric Units
Mass, Volume, & Density
• Mass is the measure of a quantity of matter. It is measured relative to a standard mass (which is why the devices to weigh an object are called Balances) Mass is not Weight.
• Volume is the amount of space a sample occupies. 1 mL = 1cm3
• Denisty – a physical property of a substance = mass/volume. Since volume increases with Temperature increase, a density is always reported with a Temperature.
Example
• A 35.66 g sample of metal as weighed and put into a graduated cylinder that contained 21.2 mL of water. The water level after the metal was added was 25.2 mL. What is the density of the metal in g/cm3
How to measure Density
• Take a substance and weight it. Then add it to a known volume of water in a volumetric flask and notice the volume change in the water as the volume of the substance. Calculate the density.
• To calculate the mass of a liquid, you add the liquid to a zeroed balance with a volumetric flask and weight the liquid. Then you have the mass and the volume, and you can caluclate the density.
Density Example Problem
• What is the volume of a 32 g sample of ethanol whose density is 0.789g/cm3 ? Report volume in cm3
Hydrometer
• If something floats on water, it is less dense then water.
• If something sinks, it is more dense then water.
• A hydrometer rises or falls to a density that is equal to the density of the liquid. It is calibrated to show the specific gravity of the liquid.
Specific Gravity• S.G. = density of test liquid/ density of reference
liquid• Note that the units cancel.• The standard reference liquid for measuring the
specific gravity of aqueous solutions is pure water at 4 deg. C. Density is 1.000g/cm3 .
• S.G. of blood is 1.028. • This means that blood is 1.028 times the density
of pure water.
Temperature
• Substances can either gain heat or lose it, depending on whether they are cooler or hotter then their environments.
• To measure heat, we must have an indication of how hot or cold something is…that is the temperature.
• It indicates how hot something is…not the amount of heat.
Kelvin, C, and F
• K = C + 273• F = 9/5 C + 32• C (F-32)(5/9)
Heat and Calorimetry
• Heat is a form of energy.• Each substance has a different capacity to absorb
heat.• A unit of heat is defined by its effect (the rise in
temperature) on a fixed mass of a reference substance.
• SI unit = joule, (J)• Non-SI commonly used = cal• 4.184 J = 1 cal
Specific Heat : Cp
• The characteristic response of a given mass of a given substance to a given amount of heat is expressed by Cp
• Cp= joules/(grams x Δ°C)
• The specific heat is equal to the heat absorbed or lost per Celsius degree change in temperature per gram of substance.
Specific Heat• The higher a substances specific heat, the more slowly it’s temperature
rises in repsonse to heating.
Calculating Specific Heat
• What is the specific heat of a substance if the addition of 334 J of heat to 52 g of that substance causes the temperature to rise from 16 C to 48 C?
Calculating Heat from Cp
• How much heat must be added to 45.0 g of a substance that has a specific heat of 0.151 J/gC to cause it’s t to rise from 21 C to 47 C ?
Calorimeter
• When the heat produced by some physical or chemical process is abosrbed into a given mass of water, the water’s T rise will allow us to calculate the heat produced by the process.
Example
• What is the Specific Heat (Cp) of an element that takes 50 Joules to heat up 400 grams from 34 deg to 76 deg.?
Calorimeter
Basal Metabolic rate
• BMR is the minimum metabolic activity of a human at rest and with an empty gi tract.
• In nutrition and metabolism, heat is more commonly given as calories.
• The rate means it is the amount of heat over a period of time…expressed in kcal/min.