Download Chem 152 Chapter 4

Chem 152 Chapter 4
Physical States of Matter
• Solid
– Definite volume and shape.
– Crystalline
– Internal geometric structure is regular and repeating.
– Salt, sugar, quartz.
– Amorphous
– Internal structure has no regular pattern.
– Plastic, glass.
• Liquid
– Definite volume but indefinite shape.
• Gas
– Indefinite volume and indefinite shape.
Movement of Particles
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As you heat a substance, its particle move faster (greater kinetic energy).
Particles in the gas phase are moving the fastest.
Liquid phase particles move with less energy than the gas phase.
Solid phase particles are the slowest but they also have movement. (vibrations).
Phase Changes
• Sublimation: solid  gas.
• Vaporization: liquid  gas.
• Melting: solid  liquid.
• Deposition: gas  solid.
• Condensation: gas  liquid.
• Freezing: liquid  solid.
• Which of these are require energy and which release energy?
Substance
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A particular type of matter with a definite, fixed composition.
Material that contains only one substance is either an element or a compound.
Elements
• Elements are the most basic form of matter.
• Cannot be broken into simpler substances by chemical or physical processes.
• A sample of an element contains only one type of atom.
• There are over 100 known elements.
– oxygen, carbon, iron, gold, helium, neon, sodium..
– Symbols: O, C, Fe, Au, He, Ne, Na...
• The elements are listed on the Periodic Table.
Diatomics
• Some elements come as a couple!
– We call them “diatomics”: H2, N2, O2, F2, Cl2, Br2, I2
– They form a 2-atom molecule when they are not combined with other atoms.
– Know these.
The Periodic Table
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Elements are arranged in the periodic table according to their properties.
Each element has an “Atomic Number”.
Metals are on the left, non-metals are on the right, metalloids between.
Properties of Metals and Non-Metals
• Metals
– Usually shiny.
– Good conductors of heat and electricity.
– Malleable and ductile.
– Most are solids at room temperature.
– High melting points.
– Can form alloys (mixtures of 2 or more metals: 14K gold: Au, Ag, & Cu)
• Non-metals
– Not good conductors.
– At room temperature, some are solid (sulfur), some are liquid (bromine), and
many are gases (oxygen, nitrogen..).
• Metalloids have properties in between.
Compounds
• Pure substance composed of 2 or more elements.
• More than one type of atom chemically bonded together.
– Molecules
• Water H2O
• Table salt, sodium chloride NaCl
• Carbon dioxide CO2
• Sugar, sucrose C12H22O11
– How many atoms are in a sucrose molecule?
• Calcium nitrate: Ca(NO3)2 1 Ca, 2 N, 6 O
Types of Matter: Mixtures
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Most things are composed of more than one type of substance.
We call these mixtures:
– A glass of tap water.
– A cake.
– Laundry detergent.
– Wood.
– Hair.
– Air.
More on Mixtures
• Mixtures may be difficult to study because they are composed of more than one
substance.
• They may not have “constant composition”
– A sample of tap water from my house may contain substances that a sample from
your house does not.
• However, in a mixture, each substance retains its own identity so we may be able to
separate the components.
Heterogeneous and Homogeneous Mixtures
• Heterogeneous
– Distinct regions with definite boundaries.
– Multiple phases
– Sugar and salt
• Homogeneous
– Solution
– No distinct regions, everywhere the same.
– Same phase
– Salt water, air, alloys
Compounds and Mixtures are Different
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In a mixture the substances are not bonded together and they retain their individual
characteristics.
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In a compound, the elements no longer retain their individual properties.
To separate the elements in a compound you must use a chemical reaction of some
type.
Physical and Chemical Properties
– A substance’s physical properties describe how it looks, feels, tastes, how heavy it is,
etc.
– A substance’s chemical properties describe how it reacts with other substances in
chemical reactions.
Physical Properties of Water
 Transparent
 Colorless
 Boiling Point 100°C (212°F)
 Freezing Point 0°C (32°F)
 Density 1.0 g/mL
 When a substances undergoes a change without changing its chemical nature, this
event is called a physical change.
 Melting, freezing, etc.
Some Chemical Properties
– Propane gas reacts with oxygen to form carbon dioxide and water (burns).
– Iron reacts with oxygen to form iron oxide (rust).
– Protein can be digested by enzymes in the stomach.
– These processes are called chemical changes.
Chemical Reactions
– Represented as a chemical equation.
– hydrogen and oxygen react to form water.
– 2H2 + O2  2H2O
– Reactants on left; products on right.
– Heat represented by .
Conservation of Mass
– No change is observed in the total mass of the substances involved in a chemical
change (reaction).
– OR: Matter is neither created nor destroyed in a chemical reaction.
– In the last example, if 11.2g of hydrogen is reacted with 88.8g of oxygen, 100.0g of
water is produced.
Energy
– Capacity to do work.
– Potential Energy
 Position.
 Chemical Potential Energy.
– Kinetic Energy
 Motion
– Units: Joules, calories.
 4.184 J = 1 cal
Chemical Potential Energy
– Energy stored in chemical bonds.
– Released in many chemical reactions.
 Heat, Light
Kinetic Energy
– Motion of objects.
– Also true for atoms, molecules.
– Higher temperature means particles are moving faster.
 More kinetic energy
Conservation of Energy
– Energy is not created or destroyed, but it may change forms.
– Chemical Energy
– Mechanical Energy
– Light Energy
– Electrical Energy
– Nuclear Energy
– Heat
Heat
– Transfer of energy from warmer temperature objects / particles to cooler
temperature objects / particles.
– Heat vs. Temperature
 2 buckets of water, one twice as full, both same T (20°C).
 Heat the buckets until both reach 50°C.
 It takes twice as much heat (calories) to bring the bucket with more water to the
final T.
Homework
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Memorize the names and symbols of the following elements (you probably know
some of these already):
– Elements #1-20 (don’t memorize their numbers!).
– Cr, Mn, Co, Fe, Ni, Cu, Zn, As, Br, Ag, Sn, I, Ba, Au, Hg, Pb, U.
p. 100 – 101: Key Concepts & Key Terms: all problems.
p. 101 – 105: Exercises: 1 –14, 17 – 34, 37 – 63, 65 – 68, 79, 81.
note: that's a lot of problems, don't feel you need to do every single one now, just do a
few of each type and save the rest for review before the exam.