Matter in Our World

Matter Made up of atoms Atoms that are all the same make an element  Every element has different types of atoms

Kinetic Theory Three main points  All matter is made of atoms and molecules  These atoms and molecules are always in motion At high temperatures, particles move faster  At the same temperature, larger atoms and molecules move slower than smaller ones

Kinetic Theory Used to describe the states of matter  Solid Solid  Liquid Liquid  Gas Gas Changing States

Solid Atoms move very, very slowly Set volume Set shape States of Matter

Liquid Atoms move around Set volume Changing shape Can look at viscosity  High viscosity = less flowing States of Matter

Gas Atoms move very, very fast Changing volume Changing shape Exerts pressure on objects  High pressure = lots of movement States of Matter

Changing States of Matter Energy makes this happen Red  Energy added Blue  Energy taken away

Changing States of Matter Total amount of matter never changes  Law of conservation of mass Total amount of energy never changes  Law of conservation of energy

Changes in Matter Chemical change  Changes the make-up of matter Different matter is made Physical change  Does not change the make-up of matter Same matter exists – just a different form

Clues to Chemical Change Change in color Production of gas Production of a solid Key words:  Burn, decay, ‘die’, ripen, rot

Clues to Physical Change Key words  Cut, tear, melt, freeze, dissolve, grind

Idea of the Atom Democritus (BC)  Had the original idea that all matter was made of a small ‘invisible’ units  Called these atoms Dalton (1800’s)  Proposed his theory of matter and the atom  Widely accepted because of his evidence

Dalton’s Atomic Theory Every element is made of tiny, unique particles that cannot be divided Atoms of the same element are exactly alike Atoms of different elements can join to form molecules

Elements ElementSymbolElementSymbol HydrogenHMg OxygenOBr SodiumNaNitrogen KSulfur IodineICa CBoron ChlorineZn IronSi AgNeon

Current Atomic Model Atoms can be divided  Protons Positive charged  Electrons Negative charged  Neutrons No charge Call these subatomic particles

Current Atomic Model Nucleus Has protons and neutrons in it Electrons are around the nucleus Number of Protons = Number of Electrons Tells us the atom is neutral (no charge)

Describing the Atom Mass Number  Number of protons added to the number of neutrons protons neutrons 9+9= 18

Mass Number Also known as the Atomic Mass Can be found on the periodic table

Describing the Atom Atomic Number  Number of protons in the atom  Found on the periodic table

Critical Thinking If Dalton were still alive, he might argue: “Atoms are neutral so they can’t be made of charged particles.” Explain why this is not true.

Periodic Table Periods Groups

Divisions of the Periodic Table

Metals Good conductors of electricity Mostly found on the left side of the table Usually solids Some are shiny (middle ones) Some are very reactive (one on far left)

Non Metals Cannot conduct electricity Most are on the right side of the table  Exception = hydrogen Can be solids, liquids or gases Can be extremely reactive (group 17) Can not react at all (group 18) One very important nonmetal  A part of every living organism = Carbon

Matter and Atoms When elements chemically combine they form compounds  The same element can combine  Different elements can combine Matter can be physically combined into mixtures  Lots of elements in the same place  Lots of compounds in the same place  Combination of elements and compounds in the same place

Matter and Atoms Elements, compounds, and molecules are all pure substances Matter also exists as mixtures  Homogenous Mixtures that look the same throughout Substances are miscible  Heterogeneous Mixtures that you can see the different substances in Substances are immiscible

Matter Chemical formulas are important for telling us what compounds are made of  Sugar – C 12 H 22 O 11 Carbon 12 atoms HydrogenOxygen 11 atoms22 atoms

Common Compounds Salt = NaCl Ammonia = NH 3 Baking Soda = NaHCO 3 Water = H 2 O Hydrogen Peroxide = H 2 O 2 Bleach = NaOCl Glass = SiO 2 Vinegar = CH 3 COOH

Acids A substance that forms H 3 O + (hydronium ions) when dissolved in water  Adds a H to water Properties  Sour taste  Conduct electricity  Reacts with metals

Strong Acids vs. Weak Acids Strong  All acid compounds completely dissolve in water  Lots of H 3 O + Weak  Not all acid compounds are dissolved in water  Not many H 3 O +

Bases A substance that forms OH- (hydroxide ions) when dissolved in water  Takes a H away from water Properties  Bitter taste  Conduct electricity  Feels slippery

Strong Base vs. Weak Base Strong  Reacts with water to form lots of OH- Weak  Forms very few OH- when it reacts with water

Detecting Acids and Bases Use an indicator  A substance that turns color when touched by an acid or base  Litmus paper - red and blue types Acids  A blue indicator will turn red when in acid Bases  A red indicator will turn blue when in base

Litmus Paper Tests

pH Scale Used to determine how acidic or basic something is Measures the concentration of H 3 O + Ranges from 0 to 14  7 is neutral  Below 7 is acidic  Above 7 is basic

pH Paper Test

Lab Data Table SolutionBlue LitmusRed LitmuspH PaperA or B

pH Scale

Neutralization A reaction between acids and bases  The hydronium (H 3 O + ) ions reaction with the hydroxide (OH-) ions  Form water and salt HCl + NaOH → NaCl + H 2 O Acid Base SaltWater