Mixtures , Compounds and Elements
Titanic
In 1912, the Titanic was the largest
ship ever to set sail. This majestic
ship was considered to be unsinkable.
Yet, on April 15, 1912, the Titanic hit
a large iceberg. The resulting damage
caused the Titanic to sink, killing
1,500 of its passengers and crew.
How could an iceberg destroy the 2.5
cm thick steel plates that made up the Titanic’s hull? Analysis of a
recovered piece of steel showed that the steel contained large amounts of
sulfur. Sulfur is a normal component of steel. However, the recovered
piece has much more sulfur than today’s steel does. The excess sulfur may
have made the steel brittle, much like glass. Scientists suspect that this
brittle steel may have cracked on impact with the iceberg, allowing water
to enter the hull.
The Ratio of Components in a Mixture
A com pound is made of elements in a specific
mass ratio. However, the components of a
m ixture do not need to be mixed in a definite
ratio. For example, granite is a mixture made
of three minerals: feldspar, mica, and quartz.
Feldspar is pink in color. Mica is black. Quartz
is
colorless.
Look
at
the
egg-shaped
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paperweights
paperweights in the Figure. The pink one is made from granite that has
more feldspar than mica or quartz. That is why it is pink. The black one is
made from granite that has more mica than the other minerals. The gray
one is made from granite that has more quartz than the other minerals.
Even though the proportions of the minerals change, this combination of
minerals is always a mixture called granite.
Properties of Compounds
As an element does, each compound has its own
physical properties. P hysical properties include
m elting point , density , and color . Compounds
can also be identified by their different chemical
properties. Some compounds react with acid. For
example, calcium carbonate, found in chalk, reacts
with acid. Other compounds, such as hydrogen
peroxide, react when exposed to light.
Properties: Compounds Versus Elements
A compound has properties that differ from those of the elements that
form it. Sodium chloride, or table salt, is made of two very dangerous
elements—sodium and chlorine. Sodium reacts violently with water.
Chlorine is a poisonous gas. But when combined, these elements form a
harmless compound with unique properties. Sodium chloride is safe to eat.
It also dissolves (without exploding!) in water.
Worksheet
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Choose the best answer:
1. In this passage, what does the word brittle mean?
a. likely to break or crack
b. very strong
c. clear and easily seen through
d. lightweight
2. What is the main idea of the second paragraph of this passage?
a. The Titanic’s hull was 2.5 cm thick.
b. The steel in the Titanic’s hull may have been brittle.
c. The large amount of sulfur in the Titanic’s hull may be responsible
for the hull’s cracking.
d. Scientists were able to recover a piece of steel from the Titanic’s hull.
3. What was the Titanic thought to be in 1912?
a. the fastest ship a float
b. the smallest ship to set sail
c. a ship not capable of being sunk
d. the most luxurious ship to set sail
4. The elements in a compound
a. join in a specific ratio according to their m asses.
b. combine by reacting with one another.
c. can be separated by chemical changes.
d. All of the above
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Applying Concepts
5. Iron is a solid, gray metal. Oxygen is a colorless gas. When they
chemically combine, rust is made. Rust has a reddish brown color. Why is
rust different from the iron and oxygen that it is made of?
A com pound has properties that differ from those of the elem ents
that form it.
Vocabulary check
6. Using the passage , give the definitions of the following terms:
a. Compound
A com pound is a substance m ade of different elem ents in a
specific m ass ratio.
b. Properties
P hysical properties are the different characteristics that include
m elting point, density, and color. Com pounds can be identified by
their different chem ical properties.
7. Proof that a compound has properties that differ from those of the
elements that form it.
Sodium reacts violently w ith w ater. Chlorine is a poisonous gas.
But w hen com bined, these elem ents form a harm less com pound
w ith unique properties. Sodium chloride is safe to eat.
Resources:
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 Holt science and Technology - Physical science.
ISBN-13: 978-0-030-46228-3
Unit two – Section one- page 66.
 SAT Science Exam KS3 , 2007.
 SAT Science Exam KS3 , 2008.
 Websites:
http://www.google.com/imgres?q=titanic+breakup+and+sinking&hl
=ar&sa=X&rlz=1T4RNRN_enUS444US445&tbm=isch&prmd=imvns&t
bnid=M6XQeFw35hQZM:&imgrefurl=http://news.nationalgeographic.com/n
ews/2012/04/120403-titanic-100-anniversary-scienceicebergs/&docid=LAqNMFvQADH72M&imgurl=http://images.national
geographic.com/wpf/media-live/photos/000/509/cache/moreicebergs-titanicsink_50944_600x450.jpg&w=600&h=397&ei=4ODUT86WMMjirAf6zrz
7Dw&zoom=1&iact=hc&vpx=280&vpy=156&dur=8375&hovh=183&h
ovw=276&tx=135&ty=129&sig=110089647691037728902&page=3&
tbnh=144&tbnw=196&start=25&ndsp=16&ved=1t:429,r:8,s:25,i:179
&biw=1280&bih=513
http://www.exploretitanic.com/wpcontent/uploads/2012/01/Titanic-Hitting-The-Icebery.jpg
http://www.google.com.qa/imgres?q=hires+the+ratio+of+elements+in+a+compound&start=87&hl=en&sa=
X&qscrl=1&nord=1&rlz=1T4RNRN_enUS444US445&biw=1280&bih=5
13&tbm=isch&prmd=imvns&tbnid=FCUl2GVfdz4inM:&imgrefurl=http:
//cnx.org/content/m23905/latest/%3Fcollection%3Dcol10699/lates
t&docid=aPIPjlrjPMXRM&imgurl=http://cnx.org/content/m23905/latest/graphi
cs18.png&w=600&h=876&ei=tO_UT9vxBYTXrQes5LD8Dw&zoom=1
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