IVGMe.- :
HOW IS A MIXTURE
DIFFERENT :FROM
A COMP()UND?
mixture: two or more
things close together
different
95
AIM
How is a mixture different
16 from a compound?
Sometimes two or more substances are mixed together.
They do not make a compound. They make a mixture. A mixture has two or more things near one another. But the parts of
the mixture have not been changed. No chemical reaction has
taken place. No new substance has been formed.
Vegetable soup is an example of a mixture. So is salt and
sand mixed together. You can still tell one part fram another.
How can we tell the difference between a compound and
a mixture? Here are some clues:
MIXTURE
NAME
96
COMPOUND
The parts of a mixture do
not change their properties.
The elements that make up a
compound lose their
properties. The new
compound has its own
properties.
A mixture may have any
amount of each of its parts.
A compound must always
have a particular amount
of one element for a given
amount of other elements.
Energy is not taken in or
given off when a mixture is
made or separated.
Energy is always taken in or
given off when a compound
is broken up or put together.
A mixture can be separated
by physical means. For
example, a strainer can
separate some mixtures.
A compound can only be
separated with a chemical
reaction. For example,
electricity can cause some
chemical reactions.
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Globe Book Company, Inc. © 1977. All righ1s reserved.
ABOUT MIXTURES
A mixture can have many kinds of matter.
It can have
elements only
or
compounds only
A.
or
elements and
compounds
c.
B.
D. An example of a mixture is salt with pepper.
The salt and pepper are just close
together. They do not react together. Properties do not change. The salt is still salt.
The pepper is still pepper. No new products are formed.
It makes no difference how much
pepper or salt there is. No exact amounts
are needed. Energy is not taken in or given
off by the molecules of the salt or the
pepper.
Salt is a compound. Pepper is a
compound. Salt with pepper is a mixture
made up of two compounds.
97
TRUE OR
FALSE
Write T on the line next to the number if the sentence is true.
Write F if the sentence is false.
1.
A mixture has exact amounts.
2.
A compound has exact amounts.
3.
The parts of a mixture keep their properties.
4.
The elements of a compound keep their properties.
5.
We need energy to make or break up a compound.
6.
Hydrogen is a compound.
7.
Water is a compound.
8.
We need a chemical reaction to separate a compound.
9.
Electricity can separate some compounds.
10.
Heat can change water to oxygen and hydrogen.
MAKING A MIXTURE AND A COMPOUND
iron filings
powdered yellow sulfur
test tube and holder
Bunsen burner
magnet
piece of paper
NAME
98
.
Globe Book Company, Inc.
___
©
1977. All righ1s reserved.
B.
A.
How To Do The Experiment, Part I
A.
B.
1.
Place a teaspoon of the sulfur on a piece of paper.
2.
Add about % teaspoon of iron filings.
3.
Mix them together.
1. Hold the magnet in the mixture. Move it around .
•
2.
Lift the magnet.
What You Learned
1. Could you tell the sulfur from the iron before using the magnet?
2.
_
The magnet lifted the
sulfur, iron
3. The magnet did not lift the
---,-,__
iron, sulfur
4.
Have you separated the iron from the sulfur?
5.
Did the properties of the iron change?
_
_
6. Did the properties of the sulfur change?
7. Was a new product formed?
_
_
8. Did a chemical reaction take place?
9.
Iron filings and sulfur together make a
_
--,-
_
compound, mixture
10.
A chemical equation
- iron mixes with sulfur.
______
be written to show what happens when
can, cannot
99
How To Do the Experiment, Part II
iron filings
c.
D.
A.
E.
1. Remove the iron filings from the
magnet. Mix them in with the
sulfur.
2.
Pour the mixture into the test
tube.
3.
Heat the test tube over the Bunsen burner until the sulfur melts.
4.
Remove the test tube from the
flame.
5.
Let the tube cool. Cover the tube
wi th a cloth. Then break it by
carefully tapping the bottom of
the test tube with a hammer.
.
6. Remove the cloth. Examine the
substance that was in the test
tube.
B.
1.
Put the magnet on the substance.
2.
Lift the magnet.
-~
F.
NAME
.-------------------
100
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Globe Book Company. Inc. © 1977. All rights reserved.
\
.:
What You Learned
1. Could you tell the sulfur from the iron after they were heated together?
2.
Did the magnet lift the iron filings?
3.
Did the properties of the iron change?
_
_
4. Did the properties of the sulfur change?
_
5.
Was a new product formed?
_
6.
Did a chemical reaction take place?
7.
Sulfur and iron filings heated together make a
8.
The equation below shows what happens when iron and sulfur are heated together.
Fe+ S ~
_
----.,-_
mixture, compound
FeS
Take a guess-the compound made from iron and sulfur is called a) iron oxide.
b) iron sulfide. c) sulfur dioxide. (Underline the correct answer.)
MIXTURE OR
COMPOUND
The chart below lists some terms and phrases that describe mixtures and compounds. Which ones describe mixtures? Which
describe compounds? Put a check [/J in the space to show your
choice.
[-_?-.~_--~->_--~~p~e~rt~s-_-c~~-_n_;~_--_----_
--=--- ". __-~~i~x~tu=r_e~__
_=-__
p_ro~~:_tie_s
_d_?_
no_t_c_~~_~~_:__
3.
--+__-.-_~_-c-o-m-p-o-u-n-d---~--_-~i
j
_
exact amounts
--t--------------------~-I
4.
no exact amounts
-----
c
-----
---
J
----------+-
energy always taken in
o!,__8ive:QQff_ _--------+---------------6. energy not taken in or
given off
separated by-chemical-5.
----- ----------
!----7~-
t
I
phYSical-means
- ----.-------~
..----_.
9. what you have in your
___
pocket <?!Jlil_g
_
--II
0-. -- :;~!ted-by-
~o:~~on
sUlfi_d_e
---------____j_
_L
101
THROW
ONE OUT
In each of the following sets of terms, one of the terms does not
belong. Circle that term.
1.
mixture
compound
water
2.
mixture
compound
salt with pepper
3.
exact amounts
no exact amounts
compound
4.
exact amounts
no exact amounts
mixture
5.
properties change
salt
properties do not change
sand with water
water
salt with pepper
chemical change
hydrogen explodes
NAME
102
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