Transcript Introduction to Chemistry

An Introduction to Chemistry,
Lab Skills, and Measurement
Unit 1
The Scientific Method is loosely defined as the way
in which a scientist goes about solving a problem.
Define a
Problem
Share this
theory with
the Scientific
Community
through Peer
Review
Evaluate
the
Problem
Collect
Observations
about the
Problem
Form a theory
to explain the
problem
Peers
repeatedly
test your
theory
Devise a
Testable
Hypothesis
Create an
Experiment to
test the
Hypothesis
Draw
conclusions that
reflect back to
the hypothesis
Make
Observations
during the
Experiment
A hypothesis is a tentative explanation for a
set of observations
tested
modified
A law is a concise statement of a relationship
between phenomena that is always the same
under the same conditions.
Chemistry is the study of matter and
the changes it undergoes, as well as the
study of chemical energy and its
transfer
1. Matter is anything that occupies space and
has mass.
2. A substance is a form of matter that has a
definite composition and distinct properties.
water, ammonia, sucrose, gold, oxygen
A mixture is a combination of two or more substances
in which the substances retain their distinct identities.
1. Homogenous mixture – composition of the
mixture is the same throughout.
soft drink, milk, solder
2. Heterogeneous mixture – composition is not
uniform throughout.
cement,
iron filings in sand
Physical means can be used to separate a mixture
into its pure components.
distillation
magnet
An element is a substance that cannot be
separated into simpler substances by chemical
means.
• 116 elements have been identified
• 82 elements occur naturally on Earth
gold, aluminum, lead, oxygen, carbon
• 34 elements have been created by scientists
technetium, americium, seaborgium
A compound is a substance composed of atoms
of two or more elements chemically united in fixed
proportions.
Compounds can only be separated into their
pure components (elements) by chemical
means.
Water (H2O)
Glucose (C6H12O6)
Ammonia (NH3)
Separating Homogenous Mixtures
• If homogeneous matter can be separated by
physical means, then the matter is a mixture.
Separation of Mixtures
Separating Homogenous Mixtures
• If homogeneous matter cannot be
separated by physical means, then the
matter is a pure substance.
• A pure substance can sometimes be
decomposed into something else, the
substance is then a compound.
Kinetic Nature of Matter
Matter consists of atoms
and molecules in motion.
v
Solid
Liquid
Gas
OTHER STATES OF MATTER
• PLASMA — an electrically charged gas;
Example: the sun or any other star
• BOSE-EINSTEIN CONDENSATE — a
condensate that forms near absolute zero
that has superconductive properties;
Example: supercooled Rb gas
Physical or Chemical?
A physical change does not alter the composition
or identity of a substance.
sugar dissolving
ice melting
in water
A chemical change alters the composition or
identity of the substance(s) involved.
hydrogen burns in
air to form water
Extensive and Intensive Properties
An extensive property of a material depends upon
how much matter is is being considered.
• mass
• length
• volume
An intensive property of a material does not
depend upon how much matter is is being
considered.
• density
• temperature
• color
Matter - anything that occupies space and has mass.
mass – measure of the quantity of matter
SI unit of mass is the kilogram (kg)
1 kg = 1000 g = 1 x 103 g
weight – force that gravity exerts on an object
weight = g x mass
A 1 kg bar will weigh
on earth, c = 9.8 m/s2
9.8 N on earth
on moon, c ~ 1.6 m/s2
1.6 N on the moon
Units of Measurement
• Powers of ten are used for convenience with smaller
or larger units in the SI system.
Units of Measurement
SI Units
Volume – SI derived unit for volume is cubic meter (m3)
1 cm3 = (1 x 10-2 m)3 = 1 x 10-6 m3
1 dm3 = (1 x 10-1 m)3 = 1 x 10-3 m3
1 L = 1000 mL = 1000 cm3 = 1 dm3
1 mL = 1 cm3
Density – SI derived unit for density is kg/m3
1 g/cm3 = 1 g/mL = 1000 kg/m3
mass
density =
volume
m
d= V
A piece of platinum metal with a density of 22.0
g/cm3 has a volume of 4.40 cm3. What is its mass?
K = 0C + 273.15
(°F - 32) * 5/9
= °C