matter & change. matter classification try to answer the following questions 1. a compound is...
TRANSCRIPT
Matter & Change
MATTER CLASSIFICATION
Try to Answer the Following Questions
1. A compound is formed by…a. A single elementb. Two or more atomsc. Two or more nucleid. Electrons and neutrons
2. Which statement best describes atoms and molecules in a liquid?a. They vibrate rapidlyb. They form a definite structurec. They slide past each otherd. They cannot be rearranged
3. What is the process of a liquid changing to a gas called?4. Ice melting into water is a physical or chemical change?5. Which state of matter has neither a definite shape nor definite
volume?
How did you do?
1. “B”: two or more atoms2. “C”: atoms and molecules in a liquid
slide past each other3. Evaporation4. Physical5. Gas
Introduction
• What is chemistry?• The study of the composition of substances and the
changes (both physical and chemical) they undergo
• What lead to the development of chemistry?• Alchemy
• What other sciences does chemistry contribute to?• Biology• Geology• Physics
Hypothesis vs. Theory vs. Scientific Law• A HYPOTHESIS is a proposed reason for what is
observed and it needs to be tested by means of an experiment• A THEORY is a thoroughly tested explanation of
why experiments give certain results.• A theory tends to explain WHY things happen.
You cannot prove a theory.• Scientific Law is a concise statement that
summarizes the results of a broad spectrum of observations and experiments.• Scientific Law tends to explain WHAT things
happen. You can prove a scientific law.
Why does it “matter”?
• What is matter?• “Everything that takes up space and has
mass”• “Stuff”
• What is mass?Amount of matter an object contains“How much stuff an object has”**This is NOT the same as weight
Substances vs Mixtures
•Matter is broken into categories. Matter can be either a substance or a mixture.
•A substance has a uniform (constant) composition. This means that no matter the sample it will always have the same physical properties (looks the same).
Two Types of SubstancesElements• Made up of only one
type of atom.• Look at the periodic
table!• Ex: Ca, K, Cl
Compounds•Made up of two or more
types of atoms.• A given compound always
contains the same, fixed ratio of elements.• Elements can combine in
different ratios to form different compounds.• Ex: Table Salt, NaClGlucose, C6H12O6
Pure Substances• Element• composed of identical atoms• EX: copper wire, aluminum foil
Pure Substances
• Compound
• composed of 2 or more elements in a fixed ratio
• properties differ from those of individual elements
• EX: table salt (NaCl)
Pure Substances• For example…
Two different compounds, each has a definite composition.
Mixtures
•A mixture is a physical blend of two or more substances. It has a variable composition, so each sample taken will have different amounts of each substance.
•Mixtures are ALWAYS physical changes
Types of mixtures
1. Heterogeneous mixtures-not uniform in composition-more than one phase (a phase is a part
of a system that is uniform in composition and physical state)
-Can be physically separated-Can visibly see differences-examples: tossed salad, gravel mix, rock,
river water
Types of Mixtures
2. Homogeneous mixtures-uniform in composition-one phase-also called a solution-easily confused with substances-examples: salt water, kool-aid
Solutions• Another name for a homogenous mixture• Can be either a liquid or gas• Phase is used to describe any part of a sample with uniform
composition and properties
Single phase 3 phases
• A good question to ask yourself when trying to decide if something is a substance or a homogeneous mixture is to ask yourself if there is more than one kind of this material.•What is gasoline?•What is milk?• Are there different concentrations of salt?if so then it is a mixture!
Examples:
• graphite
• pepper
• sugar (sucrose)
• paint
• soda
element
hetero. mixture
compound
hetero. mixture
solution
Separating a Mixture• There are several ways to separate a mixture. A
good way to figure out if matter is a substance or a solution is to see if you can separate it into parts by doing one of the following:
1. Physical separation2. Filter (particle size, uses gravity)3. Magnet (magnetism)4. Decanting-pouring off a liquid (density)5. Distillation (boiling point)6. Centrifuging (density)7. Chromatography (separates based on solubility)8. Crystallization
Properties of Matter
•Matter contains both physical and chemical properties.• A physical property is a quality of a
substance that is observed without changing the substance’s original composition.• Examples: Color, mass, density, hardness,
odor, boiling point, solubility
Chemical Properties
• Chemical properties are a little more difficult to determine. A chemical property is the ability of a substance to undergo chemical reactions.• Examples: Rot, rust, decompose, decay,
grow ferment
Chemical vs. Physical Changes
• Chemical Change• A change in the composition of a substance OR• Changing a substance to form a new substance• Examples: fermenting, rotting, burning, color change,
gas given off, heat
• Physical Change• A change in a substance without a change in its
composition• Examples: mixing, cutting, changing from a solid to a
liquid, dissolving, boiling
Figure it out- Chemical or Physical?
•Metals are shiny•Milk gets sour when left out•Metals can be made into wires•Bread rises when cooked•Nonmetals are not able to conduct electricity
P, C, P, C, P
States of Matter
• There are four states of matter: solid, liquid, gas• Solid • Liquid• Gas • Plasma –gas like
What is compressibility? Ability to squash something into a smaller volume
Solid, Liquid, Gas
(a) Particles in solid (b) Particles in liquid (c) Particles in gas
Solids• Has a definite shape
and volume• The particles are
packed close together• Are almost
incompressible, difficult to squeeze to a smaller volume• Very low kinetic energy
Liquids• Indefinite shape—takes on
the shape of the container its in• Definite volume• Flows, particles are
arranged randomly and are close, but not as close as solids• Almost incompressible• Low to moderate kinetic
energy
Gas• Indefinite shape
• Indefinite volume
• The particles are usually much
farther apart
• Gases are easily compressed
into a smaller volume
• High kinetic energy
Fourth State of Matter
• Plasma• very high KE - particles collide with enough
energy to break into charged particles (+/-)• gas-like, variable
shape & volume• stars
Kinetic Molecular Theory
•KMT
• Particles of matter are always in motion.