Matter & Its Changes
Holt – Chapter 1
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Chemistry
• 1. A physical science that studies the
composition, properties, and interaction of
matter.
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These Branches of Chemistry
study …
• Organic – carbon compounds
• Inorganic – non-organic substances
• Physical – properties of matter, changes that occur
in matter & relationships between matter & energy
• Analytical – identification of the composition of
materials
• Biochemistry – living things
• Theoretical – properties of new compounds by the
use of math and computers to design and predict
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Chemical Investigations
• Basic research – gaining knowledge about a
particular topic (i.e., reactions of an element)
• Applied research – solves a particular problem
(i.e., finding chemicals that do not cause
depletion of ozone in the atmosphere)
• Technical development – applying useful ideas
to solve problems (usually occurs long after
basic research)
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Chemical Terms
• Mass – the measure of an amount of matter.
• Matter – anything that has mass and takes up
space.
• Atom – smallest unit of matter that retains the
properties of that matter.
• Compound – formed by chemical bonding of 2
or more atom types
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Matter
Yes Can it be separated? No
Mixtures
Pure Substances
Is the Composition
uniform?
Can it be decomposed
with chemical means?
Homogeneous
Mixtures
Heterogeneous
Mixtures
Compounds
(air, kool-aid)
(blood, granite)
(water, sugar)
Elements
(H, Fe, U)
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Properties of Matter
• Physical – properties that can be measured without
changing the identity of the substance (color, density,
melting and freezing points)
• Chemical – relate to how a substance interacts with
another substance to form a different substance
• Homogeneous Mixture – uniform composition (tea,
solution)
• Heterogeneous Mixture – non-uniform composition
(peanut butter)
• Pure substance – contains only 1 kind of substance
(water)
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Matter Overview
• Matter is made up of either pure substances
or mixtures.
• Pure substances can be compounds or
elements which are both made up of atoms.
• Mixtures can be homogeneous (same
throughout) or heterogeneous (different sized
particles and substances)
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More on Properties
• Extensive – depends on the amount of matter
present (mass, amount)
• Intensive – properties of a substance (boiling
point, freezing point, density)
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Changes in Matter
• Physical – change of state or shape of a
substance without the composition of the
substance changing (ice melting)
• Chemical – involves the rearrangement of
atoms of different elements in a substance
and the formation of substances with different
physical properties (baking a cake)
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Chemical Change or Reaction
One or more substances are converted into a
different substance such as:
H
+
0
Reactants
H20
Product
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Energy and Chemistry
• Energy is either absorbed (ice melting) or
released (liquid water freezing) in all chemical
and physical changes.
• Energy is neither created nor destroyed; it
changes form (chemical energy to light energy
when fireworks explode)
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The following graph shows the relationship
between temperature and heat energy
during the phase changes of water.
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Phases of Matter
• Highest Energy to Lowest
• Plasma (many atoms have lost electrons)
• Gas
• Liquid
• Solid
• We will return to this topic when we get to
Thermochemistry (heat)
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Periodic Chart Basics
• The elements are in atomic number (# of
protons) order.
• Horizontal rows are called periods
• Vertical columns are called families or groups
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More on the Periodic Table
• Elements in the same groups or families share
similar chemical properties.
• In a period (row), elements close together tend
to have similar properties. Going across a period,
physical and chemical properties change
somewhat regularly across a period then repeat
in the next period. Elements in the same period
are in the same horizontal row.
• A family or group of elements are in the same
column.
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Metals
• Good conductors of heat and electricity
• Can be hammered or rolled into thin sheets
(malleable)
• (some) are easy to cut with a knife
• Most are solids at room temperature
• Can be drawn into strands of wire (ductile)
• Have a shiny (metallic) luster
• Have high boiling points
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Nonmetals
• Poor conductors of heat and electricity
• Most are gases
• Brittle as solids (break when pressure is
applied)
• Have low boiling points
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Metalloids
• Have characteristics of both metals and
nonmetals
• All are solids at room temperature
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Noble Gases
• Aka: Inert gases
• Gaseous state at room temperature
• Generally don’t react with other elements
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Get out old assignment:
•
•
•
•
Let’s go over:
22/19,21,24
24/1,2
25/all
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Thermal Chemistry (Heat Energy)
Energy is involved in chemical reactions.
Thermochemistry is the study of heat energy
transfers in accompanying chemical reactions
and physical changes.
Heat and temperature are NOT the same
thing.
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• Heat – energy transferred from a hotter
substance to a cooler substance.
• SI unit: joule
j
newton meter
nm
kilogram meter meter
kgm2
second2
m2
Temperature – measure of the average kinetic
energy of the particles of a substance or object.
oK, oC, K
SI unit: degree
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Temperature Conversion Equations
F = 9 C + 32
5
C = 5 (F-32)
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K = C + 273
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• Convert 72 oF to oC
• C = 5/9 (F-32)
• C = 5/9 (72-32) = 22oC
• Convert -10 oC to oF
• F = 9/5 C + 32
• F = 9/5(-10) + 32 = 14oF
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Celsius to Kelvin: T = Tc + 273.15
Problem:
1. The lowest outdoor temperature ever
recorded on Earth is -128.6 oF.,
recorded at Vostok Station, Antarctica,
in 1983. What is this temperature on
the Celsius and Kelvin scales?
Answers: -89.22oC, 183.93 K
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Specific heat capacity
The amount of energy that must be added to
raise the temperature of a unit mass of a
substance by one temperature unit.
• Units: J/g K
• For Water: 4.180 J/g K
• For Aluminum: 0.897 J/g K
• Which one heats faster?
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/steel
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• Heat Transfer Heat Transfer
Q = mCΔT = mC (Tf – Ti)
• q = mCΔT = mC (Tf – Ti)
•
•
•
•
q, quantity of heat in joule
m, mass of substance in kg
c, specific heat for water in 4.186 j/g K
t, temperature in Celsius
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See table on frame 29.
Find the amount of heat needed to change the
temperature of 5.0 g of liquid water from 8.0oC to
100oC.
q = mcDt = 5.0g(4.186 j/goC) (92oC) = 1.9 x 103 j
Again,
specific heat is the amount of
heat necessary to change one kg
of a substance 1 degree Celsius or
Kelvin.
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• 12/3 When you turn on the hot water to
wash dishes, the water pipes have to heat
up. How much heat is absorbed by a
copper water pipe with a mass of 2.3 kg
when its temperature is raised from 20.0oC
to 80.0oC?
• Q = mcDt
• Q = (2.3kg)(1000g)(0.390J)(60.0oC)
•
kg
go C
• Q = 53820 J or 5.4x104J
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Law of Heat Exchange
q lost = q gained
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• 0.300 kg of coffee, at a temperature of 95 °C, is
poured into a room-temperature (20.oC) steel
mug, of mass 0.125 kg. Assuming no energy is
lost to the surroundings, what does the
temperature of the mug filled with coffee come
to?
• Applying conservation of energy, the total
change in energy of the system must be zero.
So, we can just add up the individual energy
changes (the q's) and set the sum equal to zero.
The subscript c refers to the coffee, and m to the
mug.
• qc and qm
•
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• tf = 91.8oC
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Latent Heat is energy transferred during
phase changes
• Latent Heat
• Crystalline materials change phase -- melt and freeze or vaporize and
condense -- at a single, fixed temperature.
Energy is required for a change of phase of a substance. The ratio of the
energy to the mass of the substance involved is called the latent heat of
the substance. This is much like the specific heat we have just discussed. It
is called latent heat because there is no change or difference in
temperature.
•
Latent heat of fusion Hf describes the heat necessary to melt (or freeze) a
unit mass of a substance.
q = m Hf
• Latent heat of vaporization Hv describes the heat necessary to vaporize
(or condense) a unit mass of a substance.
• q = m Hv
•
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Temperature vs Heat
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Formulas
•
•
•
•
•
•
Temperature change use: q = mc D t
Melting or freezing: q = m Hf
Evaporation or Condensation: q = mHv
Hf is latent heat of fusion, 3.33 x 102 J/g
Hv is latent heat of vaporization, 2.26 x 103 J/g
These values are for water.
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Problem
• A jar of tea is placed in sunlight until it reaches
an equilibrium temperature of 32oC. In an
attempt to cool the liquid to 0oC, which has a
mass of l80 g, how much ice at 0oC is needed?
Assume the specific heat capacity of the tea to
be that of pure liquid water.
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m tea = 180gm ice = ? which is the mass of the water that
has melted
c tea = c water = 4.186 J/goC
H f = 3.33 x 102 J/g and t final = 32oC
Q lost = Q gained tea loses and water gains only melting
the ice
(mcDt)tea = (mHf)ice
m ice
= (mcDt)tea
Hf ice
m ice
= (0.180kg)(4.186 J/goC)(32oC)
3.33x102 J/g
= 7.2 x 10-2kg
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