Transcript Chapter 2 Introduction to Chemistry

Matter
 Properties of Matter
 Matter is anything that has mass and
volume
 Not every sample of matter is a substance.
A substance is a particular kind of matter
that has a uniform and definite
composition. Pure substances contain
only one kind of matter
States of Matter
Types of changes
 Physical – identity of substance is still the same
 Chemical – new substance with different properties
forms
 During a change in state there is no temperature
change
 Physical Properties – density, color, hardness, texture,
melting point
 Conservation of Matter states that matter cannot be
created or destroyed in an ordinary chemical reaction.
Physical Properties
 Physical property is a quality or condition of a substance
that can be observed or measured without altering or
changing the identity of a substance
 Cutting grass
 Tearing paper
 Melting ice
 Breaking glass
 These are all physical changes
Chemical Properties
 Chemical Property is the ability of a substance to undergo
chemical reactions and to form new substances (i.e.
flammability, rusting) – can only be observed during the
change
 Chemical changes can’t be observed without altering the
substance in some way that produces a new substance –
rust, digestion, and combustion
 Physical changes can be reversible by a physical change,
chemical changes are not.
Mixtures
 Classify Mixtures

Mixtures are a blend of 2 or more pure
substances. (i.e. salad, air, chicken soup, blood)
 Pure Substances in Chemistry

Single Elements

Compounds
Classify Mixtures continued…
 Heterogeneous – is not uniform, blend of different
parts very visible (2 phases)
 Separate by hand or physical means, filter
 Homogeneous – is uniform, AKA solutions, not a
visible blend (1 phase)
 Separate by distillation, crystallization/evaporation and
chromatography
Classify Mixtures continued…
 Homogeneous mixtures are so important in chemistry
that chemists give them a special name – solutions.
 Any part of a system with uniform composition and
properties is called a phase.
Separating mixtures
 Heterogeneous mixtures are separated by hand or
physical means, filtration.
 Homogeneous mixtures are separated by distillation,
crystallization/evaporation and chromatography
 Distillation – a liquid is boiled to produce a vapor
that is then condensed again to a liquid
Elements and Compounds
 Distinguishing Elements and Compounds
 Elements are the simplest forms of matter that can
exist under normal laboratory conditions.
 Compounds are substances that can be separated into
simpler substances (elements) only by chemical
means.
 What is made chemically must be broken chemically
Elements and Compounds continued…
 (Element is a substance that cannot be separated into
simpler substances by ordinary chemical means.)
 Compounds are made up of 2 or more elements that
have been chemically combined
2Mg + O2  2MgO
Symbols and Formulas
 Chemical symbol – 1 or 2 letters, 1st Capitalized, 2nd
Lower case
 Names come from Latin, or old world, Greek
Atomic number
1
Chemical Symbol
Element name
Atomic mass (amu’s)
H
Hydrogen
1.0079
Chemical Reactions
 Changing Reactants to Products
 Every substance has physical properties, each also has
properties that relate to the kinds of chemical changes
it can undergo. (i.e. iron reacts with oxygen and rusts
– iron oxide)
 Chemical reaction – 1 or more substances change
into a new substance or substances.
Chemical Reactions continued…
 Reactants are the starting substances
 Products are the substances being formed.
 Reactants  Products
 For example: A + B  AB
2Na + Cl2  2NaCl
 Arrow mean “changes into” or “yields”
 Or
How you can tell a change has
taken place?
 Change in color
 Production of a gas
 Emission of a light
 Change in heat/NRG – gets hot or cold
 Production of a precipitate (ppt)
Conservation of Mass
 Combustion or burning is an example of one of the most
familiar chemical changes.
 Upon first glance, you would think matter was destroyed,
however, careful measurements show that the total mass of
the reactants (coal and oxygen) equals the total mass of the
products (CO2, water vapor, and ash) when the mass of the
gas is taken into account.
Law of Conservation of Mass
 The Law of Conservation of mass is the reflected in
these observations and states that in any physical
change or chemical reaction, mass is neither created
nor destroyed; it is conserved.