chapter 1: matter and change
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Chapter 1: Matter and Change. 1.1 Chemistry. Chemistry is the study of the composition of substances and the changes they undergo. Can be as simple as the science behind ice melting, to as complicated as impulses carried by your nerve cells. The “Central Science” - PowerPoint PPT PresentationTRANSCRIPT
Chapter 1: Matter and Change
1.1 Chemistry Chemistry is the study of
the composition of substances and the changes they undergo.
Can be as simple as the science behind ice melting, to as complicated as impulses carried by your nerve cells.
The “Central Science” Contributes to biology,
geology and physics.
Chinese/Japanese character for chemistry literally means “change study”
1.2 The Scientific Method You’ve covered this before in other classes. Pg. 4-5 of text. Theory: A well-tested explanation for a
natural event. Law: A summary of observations about
natural events.
1.3 Properties of Matter What is matter?
Matter is anything that takes up space (has volume) and has mass.
Mass: The amount of matter than an object contains. Substances
Table sugar is 100% sugar (table sugar is sucrose). Table sugar is a substance
A substance is a kind of matter that has a uniform and definite composition.
Is lemonade a substance? Air? Water?
Physical Properties All samples of a substance have identical
physical properties. A physical property is a quality or condition of a
substance that can be observed or measured without changing the substances composition.
This is really wordy. Give me examples. Color, mass, odor, hardness, density, melting
point, and boiling point are all examples. We use physical properties to help identify
substances.
Example Pg. 8 of textbook, table 1.2 If I give you a white solid that melts at 800°C,
what substance would it probably be? How about a colorless liquid that couldn’t be
frozen in your home’s freezer? Hint: Melting point and freezing point are the same
thing.
Homework Read pg. 3-8 Do:
Pg. 6, #4 Pg. 7, #5 Pg. 8 #6 Pg. 22-25, #29, 30, 54, 59a, 62, 65
1.4 The States of Matter The same substance, like water, can exist in
multiple forms. Ice, water, steam Still all water, just different forms of it.
These forms are called physical states. Physical states are a physical property of the
matter
Solids Three main states of matter
Solids Shape does not depend
upon the shape of the container
Solids are matter that has a definite shape and volume.
Particles packed together tightly. Most are incompressible, and expand only slightly when heated.
Liquids Liquids
Particles in a liquid are in contact with each other, but packed less tightly than in a solid.
Almost incompressible, but expand when heated.
Liquid flows Takes the shape of the
container in which it is placed
However, volume remains the same for a given sample, regardless of the container.
Gases Gasses
Flow to take the shape of the container that holds them
Particles spaced far apart
Expand without limit to fill any space
Easily compressible Takes both shape and
volume of container
Gas ≠ Vapor Term gas is reserved for a substance that exists
in the gaseous state at room temperature The word vapor describes a substance, although
in the gaseous state, is generally a solid or liquid at room temperature. Water is a liquid, though it can be a vapor when
heated
1.5 Physical Changes Matter can be changed in many ways without
altering its composition. Cutting, grinding, bending, melting, freezing,
boiling These transformations that do not alter a
substance’s composition are called physical changes.
Homework Read
Pg. 9 – 11 (up until mixtures) Do
Pg. 10, #7 and 8 Pg. 11, #9 and 10 Pg. 22-25, #31, 32, 33, 61, 63
1.6 Mixtures What is it to create a mixture?
A salad is a mixture. Soil is a mixture. Lemonade is a mixture. Air is a mixture. A mixture consists of a physical blend of two or
more substances. NOT substances.
Granite, salad, air, kool-aid are all mixtures. Is there a difference in how they look though?
In general? There are different types of mixtures.
Heterogeneous Mixtures Not uniform in composition.
If you sample one portion of the mixture, will be different from any other portion.
Which of the above would be a heterogeneous mixture?
Homogeneous Mixture Completely uniform composition
Any given sample should be the same Composition can still vary
Phase Any part of a system with uniform composition
and properties Homogeneous mixtures have one phase Heterogeneous mixtures have two or more
phases Vinegar and oil dressing has 2 phases, an oil
phase and a water phase
1.7 Elements and Compounds By physically separating mixtures, you can
obtain pure substances Remember, substances have uniform and definite
compositions Two groups of pure substances
Elements Compounds
Elements Simplest form of matter that can exist under
normal laboratory conditions Cannot be separated into simpler forms by
chemical reactions Examples
Iron, sulfur, carbon, hydrogen, oxygen Fe, S, C, H2
Compounds Substances that can be separated into
simpler substances only by chemical reactions
Made when two or more elements combine chemically
Examples: Water (H2O), octane (C8H18)
Page 15 summarizes with flow-chart
Homework 12-14, 36, 38, 40, 56
1.8 Chemical Symbols All matter in the universe is made of
elements. Each element is represented by a chemical
symbol. Generally, chemical symbol consists of the first
one or two letters of the name of the element. Carbon C Lithium Li Neon Ne
Not always the case though. Some elements are derived from older Latin names. (pg. 17) Sodium Na (Natrium) Copper Cu (Cuprum) Gold Au (Aurum) Lead Pb (Plumbum)
First letter of symbol ALWAYS capitalized. Second letter (if applicable) always lowercase.
1.9 Chemical Reactions In a chemical reaction, one or more of the
substances change into a new substance. The substance(s) you start with, called the
reactant(s). The substance(s) you end with, called the
product(s) represents “are changed into” Example, iron and sulfur chemical react to
form iron sulfide.
Can be viewed as:Iron + Sulfur Iron sulfide
reactants product Indications of a chemical reaction
Energy given off or taken in (becomes warmer or colder) Color change Production of a gas or solid
Note: Some of these can occur during a physical change as well.
Chemical Properties Just like every substance has physical
properties, all have chemical properties. The ability to undergo chemical reactions and to
form new substances. Only observed when a substance undergoes a
change in composition (and therefore a chemical change) Words like rot, rust, decompose, ferment, corrode,
grow, decay, sprout, react usually signify a chemical change.
1.10 Conservation of Mass Law of Conservation of Mass
In any physical or chemical reaction, mass is neither created nor destroyed; it is conserved
In other words, the mass of the products equals the mass of the reactants
Questions Classify the following changes as physical or
chemical Bread is baked Salt dissolved in water Milk spoils A snowflake melts
Why is the conservation of mass a law and not a theory?
When powered iron is left exposed to the air it rusts. Explain why the rust weighs more than the original powered iron.
Hydrogen and oxygen react chemically to form water. How much water would be formed if 4.8 grams of hydrogen reacted with 38.4 grams of oxygen?