chem 10 chp 3
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CHEM 10 CHP 3
MATTER & ENERGY
Matter
• Anything that occupies space and has mass
• Composed ultimately of atoms
3
Structure Determines Properties
• the atoms or molecules have different structures in solids, liquid and gases, leading to different properties
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 compositionAlso known as pure substancesExamples - elements or compounds
Mixture – two or more substances that mix, homogeneous or heterogeneousExamples – coffee or cereal
See Figure 3.8: memorize!
Classifying Matter
Substances and Mixtures: DefinitionsHomogenous - uniform appearance - has
same properties throughout, like coffeeHeterogeneous - 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- Compounds are made of atoms
from two different elements, which form molecules or formula units
ELEMENTS & COMPOUNDS
Examples:
Au is symbol for atom of gold, pure element
Learn all the seven diatomic gases.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:tastecolorphysical statemelting pointboiling point
(from another textbook)
Chemical Properties
Describe the ability of a substance to form new substances, either by reaction with other substances or by decomposition.
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.
Chemical Properties of Chlorine
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 paperchange of ice into waterchange of water into steamheating 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)
Heating a copper wire in a Bunsen burner causes the copper to lose its original appearance and become a black material.
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
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.
Formation of Copper(II) Oxide
Copper(II) oxide is made up of Cu2+ and O2-
4.2
Neither Cu nor O2 contains Cu2+ or O2-A chemical change has occurred.
Water is decomposed into hydrogen and oxygen by passing electricity through it.
Decomposition of Water
The composition and physical appearance of hydrogen and oxygen are different from water.The hydrogen explodes with a pop upon the addition of a burning splint.The oxygen causes the flame of a burning splint to intensify.
They are both colorless gases.But the burning splint is extinguished when placed into the water sample.
Water decomposes into hydrogen and oxygen when electrolyzed.
reactant productsyields
CHEMICAL EQUATIONS
Water decomposes into hydrogen and oxygen when electrolyzed.
reactant yields
2H2O 2H2 O2
products
Copper plus oxygen yields copper(II) oxide.
yield productreactants
heat
Copper plus oxygen yields copper(II) oxide.
yield productreactants
heat
2Cu O2 2CuO
Law of Conservation of Mass
Antoine Lavoisier
“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
46.0 g 32.1 g 78.1 g
78.1 g product
mass productsmass products
78.1 g reactant →
mass reactantsmass reactants ==
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.
increasing potential energy
50 ft
20 ft
The potential energy of the ball increases with increasing height.
increasing 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 than the gasoline and oxygen.
• Gasoline is a source of chemical potential energy.
Types of Nonpotential EnergyMechanical/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 *TNuclear: potential energy in the nucleus of atoms Radiant or Light: E = h
Moving bodies possess kinetic energy.
• A bouncing ball.• The running man.
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.
Heat: Heat: Quantitative MeasurementQuantitative Measurement
• The SI unit for heat energy is the joule (pronounced “jool”).
• Another unit is the calorie.
4.184 J = 1 cal
(exactly) 4.184 Joules = 1 calorie
This amount of heat energy will raise the temperature of 1 gram of water 1oC.
Twice as much heat energy is required to raise the temperature of 200 g of water 10oC as compared to 100 g of water.
200 g water
20oC
A
100 g water
20oC
B
100 g water
30oC
200 g water
30oC
heat beakers 4184 J 8368 Jtemperaturerises 10oC
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:
o
Joulesgram Celcius
o
Jg C
The units of specific heat in calories are: o
caloriesgram Celcius
o
calg C
The relation of mass, specific heat, temperature change (Δt), and quantity of heat lost or gained (commonly called heat transfer) is expressed by the general equation:
ΔT = heatmass of substance)(specific heat
of substance)(q = m*cp*T MEMORIZE THIS!!
o
1638 J125 g x 27.6 C
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.
(mass)(specific heat)ΔT = q
(m)(cp)ΔT = qq = 1638 J
m = 125 g
ΔT = 52.6oC – 25.0oC = 27.6oC
o
0.475 J=
g C
cp = q/mT
cp =
(0.114 cal/goC)
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 24.0oC. If the final temperature of the water is 34.2oC, what is the specific heat of the metal?
When the metal enters the water, it begins to cool, losing heat to the water. At the same time, the temperature of the water rises. This process continues until the temperature of the metal and the temperature of the water are equal, at which point (34.2oC) no net flow of heat occurs.
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 24.0oC. If the final temperature of the water is 34.2oC, what is the specific heat of the metal?
• Calculate the heat gained by the water.
• Calculate the final temperature of the metal.
• Calculate the specific heat of the metal.
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 24.0oC. If the final temperature of the water is 34.2oC, what is the specific heat of the metal?
ΔT = 34.2oC – 24.0oC = 10.2oCtemperature rise of the water
Heat Gained by the Water
o(10.2 C) = (375 )g o
4.184 Jg C
heat gained by the water
= 41.60 x 10 J
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 24.0oC. If the final temperature of the water is 34.2oC, what is the specific heat of the metal?
ΔT = 125.0oC – 34.2oC = 90.8oCtemperature drop of the metal
Once the metal is dropped into the water, its temperature will drop until it reaches the same temperature as the water (34.2oC).
Heat Lost by the Metal
heat lost by the metal
heat gained by the water
= = 41.60 x 10 J
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 24.0oC. If the final temperature of the water is 34.2oC, what is the specific heat of the metal?
4
o
1.60 x 10 J(212g)(90.8 C)
o
0.831 Jg C)
cp =
The heat lost or gained by the system is given by:
(m) (cp) (ΔT) = q
An energy transformation occurswhenever 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.
Conservation of Conservation of EnergyEnergy
4.3
H2 + O2 have higher potential energy than H2O
energy is given offenergy is absorbed
Electrolysis of Water
(endothermic)
Burning of Hydrogen in Air
(exothermic)
higher potential energy lower potential energy
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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