K to 12 Science Module Lessons 1, 2, and 3 for Grade 7

1. LESSON 1
SOLUTIONS
7

2. DEFINITIONS OF TERMS
 Heterogenous mixtures- They arecalled when different parts of the
mixture can be identified.
 Homogeneous mixtures- They arecalled solutions. Their different parts
can’t be identified.
 Solute- Itis the component presentinsmall amount.
 Solvent- Itis the componentpresent in greater amount.
 Naturally Occurring Solutions- Solution that are found in nature.
 Manufactured/ProcessedSolutions-Solution that is manufactured or man-
made.
 Solubility- Thecharacteristic of solute that there is a maximum amount
ofsolute that can dissolvein a given amount of solventat a certain
temperature.
 Saturated solution- A solution that contains the maximum amount of
solute dissolved by a given amount of solvent.
 Unsaturatedsolution- A solution that contains less solute than the
maximum amount it can dissolveat a given temperature.

3. CHARACTERISTICS OF SOLUTIONS
HOMOGENOUS AND HETEROGENOUS
When different parts of the mixture can be identified, it is heterogeneous. An
example of a heterogeneous mixture is an icecube (solidphase) placedin a glass
of soft drink (liquidphase). Differentphases can be identified. When all the ice
cubes are melted, only one liquid phase is seen. Itis now homogeneous.
Homogeneous mixtures arecalled solutions. When you put sugar into water,
the solid becomes part of the liquid and cannot be seen. You can say that the
sugar dissolves inwater or the sugar is soluble inwater. Solutions may be
solids dissolved in liquids or gases dissolved inliquids. There are also solutions
wherea gas is dissolved in another gas, a liquid in another liquid or a solidin
another solid. Gaseous, liquid, and solid solutions are all around you. Many
commercial products aresold as solutions.

4. SATURATED AND UNSATURATED
There is a maximum amount of solute that can dissolvein a given amount of
solventat a certain temperature. This is whatis called the solubility of the solute.
Fromyour everyday experience, you also observethat there is a limit to the
amount of sugar you can dissolvein a given amountof water.
The solution that contains the maximum amountof solute dissolved by a given
amount of solventis called a saturated solution. If you add more solute to the
solvent, it will no longer dissolve. The solution has reached its saturation point.
The presence of an excess solid which can no longer dissolveis evidence that the
solution is saturated.
A solution is unsaturated when it contains less solute than the maximum amount
it can dissolveat a given temperature. Itis difficult to conclude that the
containers with all solids dissolved are unsaturated simply by observing them.
Some of these may already hold the maximum amount of solute, which cannot be
observed by the unaided eye. If they do, then these are classified as saturated
solutions. A more measurableway to find out the solubility of a solute is to
determine the maximum amount that can be dissolved in 100 g of solvent at a
specific temperature.
At Figure 2, at 25oC, a saturated solution of table salt has only 36.0 g (3 tablespoons) dissolved
in 100 mL of water. Any additional table salt will no longer dissolve.

5. CONCENTRATION OF SOLUTION
The concentration describes the relative amounts of solute and solventin a given
volume of solution. When there is a large amount of dissolved solutefor a certain
volume of solvent, the solution is concentrated.
A dilute solution has a small amountof dissolved solute in comparison to the
amount of solvent.
You will be able to distinguish between concentrated and dilute solutions froma
simple demonstration your teacher will perform. You will describethe
concentrations of solutions qualitatively (by simply observing their appearance)
and quantitatively (by comparing the number of drops per volume of water).
Some of them were able to describethe solutions as having quantitative
concentrations of 1 drop/50 mL and 10 drops/50 mL. Qualitatively, you were able
to distinguish the bottle with 10 drops/50 mL moreconcentrated (darker) than
the bottle with 1 drop/50 mL.
Add very few drops of blue food coloring. It is light.

6. Add many drops of food coloring. It is now dark.
Now that you have distinguished dilute fromconcentrated solutions qualitatively
and quantitatively, you can express concentration in other ways such as:
 Percent by volume, which is the amount of solute in a given volumeof
solution expressed as grams solute per 100 millliter of solution (g/100 mL)
 Percent by mass, which is the amount of solute in a given mass of solvent
expressed as grams solute per 100 grams of solution.
Problem:
How many mL of ethyl alcohol are presentin a 50 mL bottle of rubbing alcohol?
Calculationof this problem:
Since rubbing alcohol contains 70% ethyl alcohol, it means that 100 mL of rubbing
alcohol contains 70 mL ethyl alcohol. So, the following calculations show that in
50 mL of rubbing alcohol, there is 35 mL ethyl alcohol. 50mL dividedby 70mL
multipliedby 100mL=35mL.
x 100 mL rubbing alcohol = 35 mL ethyl alcohol
All portions of a solution have the same concentration. The composition of one
part is also the sameas the composition of the other parts. But you can change
the concentration of solutions. This means you can prepare differentsolutions of
sugar in water of different concentrations (for example, 10%, 20%, or 30%). In the
same way, you can preparedifferent solutions of salt in water.
50 mL rubbing alcohol
70 mL ethyl alcohol

7. ADDITIONAL INFORMATIONS
 Increasing thetemperature either makes a solid dissolvefaster or slower in
water. For some solutes, increasing the temperature does not haveany
effect on how fast the solute dissolves.
 A solute dissolves faster in water when you increase the temperature. But
the effect of temperature is not that simple. The type or nature of the
solute will affect how fast it dissolves inwater.
 Sugar dissolves faster in hot than in cold water, and salt dissolves faster in
hot than in cold water because it practicaly melts the salt andsugar
therefore making it quicker todissolve.
 Sugar dissolves faster than salt in water. Salt has stronger bonds than sugar.
That is whatmakes sugar dissolvefaster becauseit has weaker bonds and
structurethan salt. To simplify a little, you can take as a general rule
that the higher the temperature, the faster achemical reaction occurs,
because activation energy of the reaction (the energy the individual
molecules need to overcomein order to react; in this case the energy to
break the bonds that bind the sugar molecules together) is available to a
greater fraction of the reacting molecules -> the overallreaction proceeds
faster.
 Stir coffee after adding sugar to fully dissolvethe sugar in the hot coffee. It
is to mix the sugar in the drink so that it dissolves anddoesn't just stay at
the bottom, and you can have an equal amount of sweetness in the whole
drink.
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End of Lesson 1

8. LESSON 2
MIXTURES
7

9. DEFINITIONS OF TERMS
 Mixtures- They contain two or morecomponents. These components may
vary in size. The variation in size may tell whether a mixture is homogeneous
or heterogeneous.
 Heterogenous mixtures- They arecalled when different parts of the mixture
can be identified.
 Homogeneous mixtures- They arecalled solutions. Their different parts can’t
be identified.
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GALLERY
FIGURE OF MIXTURES:
HETEROGENOUS MIXTURE:

10. HOMOGENOUS MIXTURE:

11. ADDITIONAL INFORMATIONS
 Different separation techniques makecomponents of a homogeneous
mixture more distinguishable, that is, those “unseen” components when they
are in a solution become “seen”. Justlike in the activity below, distillation and
evaporation will help you “see” the two major components of seawater —
water and salt.
During boiling, the temperature of a substance changes at the
 During melting, a substancemelts completely/smoothly within a shorttime;
while a mixture has portions that seem to be not melting.
 Many things around you are mixtures. Some are solid like brass and rocks, or
liquid like seawater and fruit juices, or gas like air. Mixtures contain two or
more components. These components may vary in size. The variation in size
may tell whether a mixture is homogeneous or heterogeneous.
 There are mixtures that are homogeneous which may be mistaken as
substances. Being so, appearance may not be the best basis to differentiate
substances frommixtures. However, thereare ways to tell by noting how a
sample behaves during boiling and melting.
End of Lesson 2

12. LESSON 3
SUBSTANCES
7

13. DEFINITIONS OF TERMS
 Compounds- They arelike mixtures, compounds are also made up of two or
more components.
 Elements- Thereare 118 elements. Each element has different set of
properties. No two elements have the sameset of properties.
 Electrolysis- This process allows you to “see” for yourself components what
this homogenous mixture is made of. With the passageof electric current,
components of water may be separated fromeach other. You will use an
improvised electrolysis apparatus. Commonly available materials were used
to constructthis improvised apparatus.
 NutritionFacts List-Itis a list of the different nutrients provided by the food
productwith their corresponding percentageshareon the daily
recommended dietary allowance. Refer to the figure on the right. Notice that
some of these nutrients are elements such as calcium.
 Periodic Table of Elements- A chartof the chemical elements thatdisplays
them in rows horizontally in order of increasing atomic number and vertically
according to similarity of the chemical properties of their atoms.
SUBSTANCES
All substances arehomogeneous. Somemixtures are also homogeneous. Being
so, it is difficult to distinguish mixtures and substances based on appearance.
However, there are ways to tell if a sample is a mixture or a substance. The
temperature of a liquid mixture varies during boiling but for a liquid substance, it
does not. A solid mixture has portions that do not melt but a solid substance
melts completely within a shorttime. In this module, you will find out that
substances may be further classified into two: compounds and elements. You will
startwith the primary characteristic that distinguishes them.

14. Chart of Parts of Matter
 Compounds are like mixtures, compounds arealso made up of two or more
components.
 Elements havedifferentset of properties. No two elements havethe same
set of properties.
Electrolysisis the process thatallows you to “see” for yourself components what
this homogenous mixture is made of. With the passageof electric current,
components of water may be separated fromeach other. You will use an
improvised electrolysis apparatus. Commonly available materials were used to
constructthis improvised apparatus. The parts of an electrolysis are electrolysis
syringe, sample container, stainless screw, redwire that contains positivepart
of dry cell, and black wire that contains negative particles of dry cell. Look at the
picture below.
Matter
Mixtures
Compounds Elements
Substances

15. An improvised electrolysis apparatus

16. The Nutrition Facts is a list of the different
nutrients provided by the food productwith their
corresponding percentageshareon the daily
recommended dietary allowance. Refer to the
figure on the right. Notice that some of these
nutrients are elements such as calcium. Is this
food a good sourceof calcium?
On the other hand, Ingredientsgive you a list of
the materials that have been added to make the
food product. These materials are the sources of
the nutrients. These are the ones that are taken in
by the body. Refer to the figure below. Find the
ingredient ferroussulfate. Ferrous is derived from
the Latin name of iron. The elements in food are
in combination with other elements and the
resulting compounds arereferred to as minerals.
Thus, you are not eating the elements
themselves. Any ingredient added to food should
be safe to eat in terms of quality
and quantity. By quality, these ingredients must
be food grade. A substance
undergoes a process beforeit becomes food
grade. Itis only after that, a
substancemay be safely added as a food
ingredient. If it is a non-food
grade substancethen it should not be added to
products that are meant to
be ingested.
Refer to the productlabels for a soy
sauceand a lotion. Notice that potassium
sorbate is a common ingredient. It has the
same function for both products, thatis, it
acts as a preservativeso the productwould
last longer. However, it is important to note
that food gradepotassiumsorbatewas
added in soy sauce; while a non-food grade
potassiumsorbatemay be added in the
lotion.

17. Periodic Table of Elements is a chart of the chemical elements thatdisplays them
in rows horizontally in order of increasing atomic number and vertically according
to similarity of the chemical properties of their atoms.
As you haveseen, elements are partof almost anything around us —food,
clothes, rocks, and even this paper you are currently reading from.
Elements aresaid to be the building blocks of matter. They are like blocks that
you can put together and build something new. When you build something new
fromthese elements, you call them as compounds. With the 118 elements,
imagine how many combinations of elements you can make into compounds and
how diversethe materials around us can be. Elements are the simplest formof
matter. Both elements and compounds aresubstances. Compounds and mixtures
are not the same. A compound is a substancewhile a mixture is composed of any
substances mixed or combined together to make a mixture.
Although, some mixtures are very hard to identify what are the substances in
those mixtures and some are very easy to identify what are the substances in
those mixtures.
End of Lesson 3