Download Chapter 3: Matter – Properties and Changes Properties of Matter

Chapter 3: Matter – Properties and Changes
Properties of Matter
States of Matter
From Creative Commons Introduction to Chemistry: General, Organic, and Biological, Chapter 8 under a Creative Commons by-nc-sa 3.0 license.
http://2012books.lardbucket.org/books/introduction-to-chemistry-general-organic-and-biological/s11-solids-liquids-and-gases.html
Instead of the old definite volume definite shape definitions, visualize the particles in solids,
liquids, and gases
From Wikipedia. http://en.wikipedia.org/wiki/State_of_matter
Notice that in the solid to liquid transition, bonds are weakened and the material becomes
fluid. In the liquid to gas transition, bonds are broken and particles are free.
Where does the energy go in the gas to plasma transition? Answer: electrons are stripped
from atoms creating a positive ion, hence ionization.
Properties of Matter
Physical properties: can be observed or measured without changing the chemical identity (or
composition) of the sample
Intensive properties are independent of sample size (density, temperature, color)
Extensive properties are dependent on sample size (mass, volume, heat)
Physical changes alter the substance without changing its chemical identity such as phase
changes or dissolution
Chemical properties: ability of a substance to change the chemical identity (or composition)
of the sample
If a substance is not combustible, this is considered a chemical property
Chemical changes always alter the chemical identity or composition of a substance
Law of Conservation of Mass: mass reactants = mass products
(Antoine Lavoisier) matter is neither created nor destroyed in a chemical reaction – it is
conserved (See Example Problem 3.1 on page 78 of the text)
Example: Practice Problem 5 on page 78 of the text
Use the data in the table to answer the following questions:
Aluminum and Liquid Bromine Reaction Substance Before Reaction After Reaction Aluminum 10.3 g 0.0 g Liquid Bromine 100.0 g 8.5 g Compound 0.0 g How many grams of bromine reacted?
How many grams of compound were formed?
Ans: 100.0 g – 8.5 g = 91.5 g
Ans: 10.3 g + 91.5 g = 101.8 g
Mixtures
Homogeneous (or solution): constant composition throughout, only a single phase
Heterogeneous: individual substances remain distinct, multiple phases with phase
boundaries or interface layers
Indicators of a chemical reaction
1. Energy evolution (heat / light / temperature change)
2. Evolution of a gas
3. Formation of a precipitate
4. Color change
5. Odor
Separating mixtures: can be accomplished by physical means
Filtration
Crystallization
From: Wikipedia http://en.wikipedia.org/wiki/Recrystallization_%28chemistr
y%29 Sublimation
From: Wikipedia http://en.wikipedia.org/wiki/Deposition_%28physics%29 Chromatography
From: WikiLectures http://www.wikilectures.eu/index.php/Filtration Distillation
Used by permission: https://uk.vwr.com/app/Header?tmpl=/chromatography/t
hinlayer_chromatography%20.htm From: Wikipedia http://en.wikipedia.org/wiki/Simple_distillation#Simple_dis
tillation Elements and Compounds
Element: a pure substance that cannot be separated into simpler substances by chemical or
physical means
The smallest particle of an element is the atom
The periodic table lists the 92 naturally occurring elements and man-made elements
occurring after uranium
Examples of element names and symbols: sodium (Na) and chlorine (Cl)
Periodic table
s
p
d
f
Rows are called periods or series
Columns are called groups or families
Compound: a pure substance composed of two or more types of elements that can be
decomposed by chemical means
Electrolysis is often used to decompose compounds into elements
Law of Definite Proportions: the elements which compose a compound always occur in the
same proportions by mass
mass of element
/ mass of compound ) x 100%
Percent mass = (
Example: Find the mass percent of sodium in sodium chloride (NaCl)
Na
= 23.0 g
Cl
= 35.5 g
%Cl = ( 35.5 g / 58.5 g ) x 100% = 60.7%
NaCl = 58.5 g
Na represents the remainder = 39.3%
Law of Multiple Proportions: if two compounds are formed by the same elements and the
same mass is used for the first element, the ratio of the masses of the second element will
occur as a small, whole number ratio
Example: Water (I) and hydrogen peroxide (II)
(I)
H : O = 11.1 g : 88.9 g (divide both by 11.1 g gives) 1 : 8
(II)
H : O = 5.9 g : 94.1 g
(divide both by 5.9 g gives)
1 : 16
Note that the oxygen masses now have a ratio of 8 : 16 or 1 : 2