Matter & Change

MATTER CLASSIFICATION

Try to Answer the Following Questions 1. A compound is formed by… a.A single element b.Two or more atoms c.Two or more nuclei d.Electrons and neutrons 2.Which statement best describes atoms and molecules in a liquid? a.They vibrate rapidly b.They form a definite structure c.They slide past each other d.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 atoms 2.“C”: atoms and molecules in a liquid slide past each other 3.Evaporation 4.Physical 5.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 Substances Elements 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, NaCl Glucose, C 6 H 12 O 6

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 phase3 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 separation 2.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.