In This Lesson:
Unit 1
Matter and
Change
(Lesson 1 of 6)
Today is Monday,
February (!) 1st, 2016
Pre-Class:
Identify the “chemistry”
in this scene
(and I don’t mean
between the people).
Hint:
There are chemical
changes and physical
changes going on.
Where are they?
http://misslolasays.com/wp-content/uploads/2011/05/barbecue.png
Today’s Agenda
•
•
•
•
Matter
Forms of matter
Changes in matter
Fire?
http://civilianmilitaryintelligencegroup.com/wp-content/uploads/2010/08/en-greek-fire.jpg
By the end of this lesson…
• You should be able to distinguish between
physical and chemical changes.
• You should be able to interpret a basic
chemical reaction.
“What’s a matter?”
• First, where is this in my book?
– P. 39 and following…
“What’s a matter?”
• What you might call “stuff,” scientists call matter.
• Matter is anything that has mass and volume (takes
up space).
– Things that are not matter:
• Love
• Religion
• Green
– Things that are matter:
• Just about everything you could touch.
• Chemistry, then, is the study of matter and change.
Phases of Matter
• You probably learned about the phases of
matter long before you even remember:
– Solid
– Liquid
– Gas
• That’s all of ‘em, right?
– There’s also plasma and Bose-Einstein
Condensates and a bunch of other stuff…
– We’ll talk about ‘em…
Phases of Matter
• So that we’re all on the same page…
– Solid:
– Liquid:
– Gas:
– Plasma:
Transitions
• As you know, matter is not always stuck in one
phase. Take water, for example. As a…
– …solid, we call it ice.
– …liquid, we call it water.
– …gas, we call it water vapor.
• And what determines which state it’s in?
– Temperature (and pressure, too)
• Plus, there really distinct points at which these
changes occur.
Matter and Change
• There are two types of changes that can occur in
matter, physical and chemical.
– Physical changes occur when only the form of a
substance has changed.
• In other words, the substances are not changed into different
substances.
– Chemical changes occur when a substance changes
into another substance (the composition changes).
• Most chemical changes come along with some distinct signs
(two slides).
• Physical changes can be undone.
• Chemical changes tend to be irreversible.
Physical Changes in Matter
• Going from a solid to a liquid is called:
– Melting (or fusion)
• Going from a liquid to a gas is called:
– Evaporating (or vaporization)
• Going from a gas to a liquid is called:
– Condensing
• Going from a liquid to a solid is called:
– Freezing (or solidification)
• Going from a solid to a gas is called:
– Sublimation
• Going from a gas to a solid is called:
– Deposition
Chemical Changes
• You are probably witnessing a chemical
change if you detect:
– Color changes
– Odor changes
– Energy changes (as in heat)
• Important: Dissolving processes sometimes give off or
absorb heat. Dissolving is a physical change.
– Production of gases or solids
Examples of Physical
and Chemical Changes
• Leaves changing color
– Chemical change
• Cooking a burger
– Chemical change
• Melting an ice cube
– Physical change
• Rotting meat
– Chemical change
• Rain forming and falling
– Physical change
• Dissolving salt into water
– Physical change
More Examples of Changes
• Let’s further investigate physical and chemical
changes with a lab!
– Chemical and Physical Changes Activity
Writing Chemical Reactions
• All chemical reactions have reactants and products.
– The starting “ingredient(s)” are the reactants while the
product(s) are the end result(s).
• They are typically written like this:
Reactant + Reactant  Product + Product
OR
Reactant + Reactant  Product + Product
IMPORTANT NOTE: The arrow means “yields.”
Writing Chemical Reactions
• Examples:
• H2 + O2  H2O
– Reactants: Hydrogen (H2), Oxygen (O2)
– Products: Water (H2O)
• 2Fe + 3H2O  Fe2O3 + 3H2
– Reactants: Iron (Fe), Water (H2O)
– Products: Rust (Fe2O3), Hydrogen (H2)
Writing Chemical Reactions
• Which is the reactant? Which is the product?
– 2H2O  2H2 + O2
• Reactants:
– 2H2O
• Products:
– 2H2
– O2
More on Chemical Reactions
• Scientists sometimes use symbols to describe
what form the reactants or products are in:
•
•
•
•
(s) means the item is a solid
(l) means the item is a liquid
(g) means the item is a gas
(aq) means the item is aqueous (it’s dissolved but
isn’t a liquid)
Conservation of Mass/Matter
• In any chemical reaction, mass is conserved.
– In other words, the mass of the reactant(s) is the same as
the mass of the product(s).
– The elements on one side of the equation are the same as
those on the other.
– Matter cannot be created nor destroyed.
• This is called the Law of Conservation of Mass.
• Sometimes it is called the Law of Conservation of
Matter.
– Because if you’re conserving matter, you’re also
conserving mass.
Aside: Chemistry History
• Among other things, AntoineLaurent de Lavoisier
discovered something
concerning the Law of
Conservation of Mass.
– He noticed that rusting iron
gained mass.
• What was the mass coming from?
• So what came of Lavoisier?
– He was beheaded during the
French Revolution. Sacre bleu!
Antoine-Laurent de Lavoisier
http://upload.wikimedia.org/wikipedia/commons/6/6c/Antoine_lavoisier_color.jpg
Aside: How Much Does A Soul Weigh?
• Meet Dr. Duncan MacDougall.
• In 1907, Dr. Mac decides to see if he can
measure the mass of a soul.
• Since matter can neither be created nor
destroyed, Mac (or “Om,” as he was called),
measured the masses of six patients as they
died on the table:
– Two tests were invalid.
– Two showed a drop in mass, then an increase.
– One showed a drop, then increase, then drop.
• The first test performed registered a drop of
0.75 ounces, or 21 grams, hence the
common “legend.”
– MacDougall did the same tests with dogs and
found no such results.
http://boingboing.net/images/_images_front_picture_library_UK_dir_13_fortean_times_6877_12.jpg
Conservation of Mass/Matter
• Another way to look at the Law of Conservation of
Mass (or Matter) is the difference between mass and
weight.
• Mass is the amount of matter in a substance. That
doesn’t change.
• Weight is the effect of gravity on an object’s mass.
– You even have slightly different weights on the equator as
at the pole (more at the pole, due a lower rotation rate).
• Compare:
– http://www.exploratorium.edu/ronh/weight/
The Law of Conservation of Mass
• It’s time we had a little firsthand experience
with the Law of Conservation of Mass.
– Conservation of Mass Lab!