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CHEM 10
CHP 3 MATTER & ENERGY
Matter
Anything that occupies space and has mass
Composed ultimately of atoms
Structure Determines Properties
the atoms or molecules have different structures in solids, liquid and gases, leading to different properties
See Figure 3.4 Three states of matter
Classifying Physical States of Matter:
Solid: it has a definite shape and volume
Liquid: it has a definite volume, but no shape; takes on shape of container
Gas: it has no definite shape and no definite volume (fills shape of container, but mostly empty space)
TYPES OF SOLIDS
Crystalline: regular repeated patterns
Salt, sugar, quartz
Amorphous: no patterns
Plastic, gel, glass
Substances and Mixtures
Substance - matter with a definite , fixed composition
Also known as pure substances
Examples - elements or compounds
Mixture – two or more substances that mix, homogeneous or heterogeneous
Examples – coffee or cereal
See Figure 3.8: memorize!
Substances and Mixtures: Definitions
Homogenous - uniform appearance - has same properties throughout, like coffee
Heterogeneous - contains two or more physically distinct phases, like ice cubes in water or oil on top of water
Phase - homogeneous part of system - separated by boundaries
System - body of matter under consideration
Elements
Fundamental/elementary substances that cannot be broken down by chemical means into simpler substances
Atom is the smallest particle of an element
91 elements occur naturally in nature
Compounds
Made of two or more elements with some type of bonding arrangement
Examples: water H2O, ethanol CH3CH2OH, sugar (sucrose) C12H22O11, table salt NaCl
ELEMENTS & COMPOUNDS
Element names and symbols:
- Elements are made of atoms or diatomic molecules (seven diatomic gases)
- Compounds are made of atoms from two different elements, which form molecules or formula units
Examples:
Au is symbol for atom of gold, pure element
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H2 is symbol for a diatomic molecule for pure element hydrogen
H2O consists of a molecule that has two hydrogen atoms and 1 oxygen atom
Properties of a Substance
A property is a characteristic of a substance
Each substance has a set of properties that are characteristic of that substance and give it a unique identity
Physical Properties
The inherent characteristics of a substance that are determined without changing its composition.
Examples:
Taste, color, physical state, melting point, boiling point
Table of physical properties of chlorine, water, sugar, and acetic acid
Chemical Properties
Describe the ability of a substance to form new substances, either by reaction with other substances or by
decomposition.
Chemical properties of chlorine
It will not burn in oxygen.
It will support the combustion of certain other substances.
It can be used as a bleaching agent.
It can be used as a water disinfectant.
It can combine with sodium to form sodium chloride.
Physical Changes
Changes in physical properties (such as size, shape, and density) or changes in the state of matter without an
accompanying change in composition.
Examples:
tearing of paper, change of ice into water, change of water into steam, heating platinum wire
No new substances are formed.
Chemical Changes
In a chemical change new substances are formed that have different properties and composition from the
original material. (Same as chemical properties)
Formation of Copper (II) Oxide
Heating a copper wire in a Bunsen burner causes the copper to lose its original appearance and become a black
material. The black material is a new substance called copper (II) oxide. Copper is 100% copper by mass.
Copper (II) oxide is 79.94% copper by mass and 20.1% oxygen by mass.
The formation of copper (II) oxide from copper and oxygen is a chemical change. The copper (II) oxide is a
new substance with properties that are different from copper.
Chemical Equations
Water decomposes into hydrogen and oxygen when electrolyzed.
The reactant, water, yields the products, hydrogen and oxygen.
2 H2O  2 H2 + O2
Table: Physical or Chemical Changes of Some Common Processes
Law of Conservation of Mass
Antoine Lavoisier
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“Matter is neither created nor destroyed in a chemical reaction”
The total amount of matter present before a chemical reaction is always the same as the total amount after
The total mass of all the reactants is equal to the total mass of all the products
sodium + sulfur  sodium sulfide
2 Na
+ S  Na2S
46.0 g + 32.1 g  78.1 g
78.1 g reactant  78.1 g product
mass reactants = mass products
ENERGY!!!!
Energy is the capacity to do work
Two main forms of energy:
Potential
Nonpotential
Potential Energy
Energy that an object possesses due to its relative position.
Stored energy: positional, chemical, etc.
(see potential energy of the ball increase with increasing height)
Gasoline is a source of chemical potential energy.
The heat released when gasoline burns is associated with a decrease in its chemical potential energy.
The new substances formed by burning have less chemical potential energy that the gasoline and oxygen.
Types of Nonpotential Energy
Mechanical/kinetic: Energy matter possesses due to its motion.
KE = ½ mv2
Chemical: produced in reactions; potential energy in the attachment of atoms or because of their position
Electrical: kinetic energy associated with the flow of electrical charge
Heat or thermal: q = m * cp *T
Nuclear: potential energy in the nucleus of atoms
Radiant or Light: E = h
Moving bodies possess kinetic energy.
A bouncing ball
The running man
Heat: Quantitative Measurement
Heat: a form of energy associated with small particles of matter
Temperature: a measure of the intensity of heat, or of how hot or cold a system is.
The SI unit for heat energy is the joule (pronounced “jool”). Another unit is the calorie.
4.184 Joules = 1 calorie; 4.184 J = 1 cal (exactly)
This amount of heat energy will raise the temperature of 1 gram of water 1oC.
The specific heat (capacity), cp, of a substance is the quantity of heat required to change the temperature of 1 g
of that substance by 1oC. The units of specific heat in Joules are Joules/gramoCelsius or in calories it’s cal/goC..
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Table: specific heat of selected substances
The relation of mass, specific heat, temperature change (Δt), and quantity of heat lost or gained (commonly
called head transfer) is expressed by the general equation:
q = m*cp*T
MEMORIZE THIS!
Calculate the specific heat of a solid in J/goC and in cal/ goC if 1638 J raise the temperature of 125 g of the solid
from 25.0oC to 52.6oC.
(Show work here.)
A sample of a metal with a mass of 212 g is heated to 125.0oC and then dropped into 375 g of water at 240.0oC.
If the final temperature of the water is 34.2oC, what is the specific heat of the metal?
(Show work here.)
Conservation of Energy
An energy transformation occurs whenever a chemical change occurs.
If energy is absorbed during a chemical change, the products will have more chemical potential energy than the
reactants.
If energy is given off in a chemical change, the products will have less chemical potential energy than the
reactants.
Law of Conservation of Energy
Energy can be neither created nor destroyed, though it can be transformed from one form of energy to another
form of energy.
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