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.