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GRADE 7 SCIENCE

Learner's Material
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Department of Education
Republic of the Philippines

Unit 1
Module 1
Solutions
     Overview
   
   In grade 6, you have learned about different mixture and their characteristics. You have done activities where you mixed a solid and a liquid or combined two different liquids. In the process of mixing. You have observed that these mixtures either from homogeneous or heterogeneous mixtures. You have seen that when all parts of the mixture have the same uniform appearance and properties, it's homogeneous.
    
    You also learned that when different parts of the mixture are visible to the unaided eye and these parts are obviously different from one another, it is heterogeneous. A heterogeneous mixture consists of two or more phases. an example of a heterogeneous. Mixtures of ice cubes (solid phase) placed in a glass of drinking water (liquid phase)

     Solutions are homogeneous mixtures. When you put sugar into water, solutions may be solids dissolved in liquids or gasses dissolved in liquids. There are also solutions where a gas is dissolved in another gas. A liquid in another liquid or a solid in another solid. gaseous, liquid and solid solutions are all around you. Many commercial are solid as solutions.

       In this module. you will identify same important properties of solutions using different methods. you will also learn how to report the amount of the components in the given volume of solution. Towards the end of the module, you will investigate the factors that affect how fast solid dissolves in water. At the end of module 1, you will be able to answer the following questions.

 What common properties do solutions have?
answer: All solutions can be melted, frozen, or be evaporated at a specific temperature
 Are solutions always liquid?
answer: No, they can be solid, liquid, or gas

 _________________________________________________________________________________

Activity 1
What solutions do you find in your home?

   After this activity, you will be able to:
  1. Describe some observable characteristics of properties of common solutions found at home or in stores; and
  2. Present the data gathered in table form to show some properties of common solutions you observed.
Procedure:

  1. With your group, mates, write the names of the products or items brought from home and describe the characteristics of each of these products. You may make a table similar to the one below.
     Products found at home
     Characteristics
    1.  Sugar
    2. Milk
    3. Water
    4. Salt
    Sweet, can be dissolved in water
    Sweet, can be evaporated
    Tasteless can be evaporated
    Salty, can be dissolved in water

  2. As you observe each product, describe the product in terms of color and appearance, odor, feel and taste (for food products).
  3. Based on what you have learned so far in grade 6, which of the products you observe are homogeneous? answer: milk what common characteristics do the homogeneous mixtures in your list have? answer: can be evaporated
  4. Which of these products or items are in solutions? answer: salt and sugar
_________________________________________________________________________________

The solution is not always a liquid, it can be solid, liquid or gas. In addition, solutions may either be found in nature or are manufactured.

MODULE 3: ELEMENTS AND COMPOUNDS0

In this module, students will begin to broadening and deepen their knowledge about substances. They begin to know that substances, like mixtures, are of various kinds. Being so, like mixtures which may be classified in many ways such as solutions, suspensions, and colloids; Substances substances can also be classified into smaller groups, such as elements and compounds.

Key questions for this module:
How are elements different from compounds?
How are they similar?

ACTIVITY 1: WATER "WAT-ER" YOU MADE OF?

In module 2, students have learned that substances and mixtures share some similarities such as homogeneity. All substances are homogeneous while only some mixtures are. Also, they learned that being homogeneous does not automatically say that a simple is made up of only one component. This holds true for one group of substances-the compounds.
Compounds are homogeneous which are also made out of components. In this activity, the students will separate components from widely used compound-water. They will learn that water is made up of the elements: hydrogen and oxygen. The properties of each of these substances are different from one another. Components of water are separated by the passage of an electric current, hence the process is termed as "electrolysis". The student will use an improvised electrolysis apparatus. You will find below how to construct one from available materials.

Reminders
  • Acquaint the students with the activity Emphasize some parts because they will be mentioned in the activity procedure.
  • Prepare ahead 5% NaOH. You may either use NaOH pellets or liquid soda.
  • NaOH pellets. Place 100 ml distilled water in a beaker. Dissolve carefully 5g NaOH pellets (corrosive). Store NaOH solution in PET bottle labeled with its name, Concentration, and date of preparation. NaOH absorbs Co2 from the air. Its concentration could change after some time.
  • Liquid soda. Mix through 1mL liquid soda and 20 mL water.

Teaching tips
  • Run down the procedure before doing the activity. Together, visualize what is supposed to be done. Have on complete setup the students can look at while emphasizing some procedures. ask some questions as you go through each step, for example: 

Procedure 1: What are the components of a 5% sodium hydroxide solutions?(sodium hydroxide and water.) How much in percentage is each of these components are in the said solution?(95% water and 5% sodium hydroxide.) what is the component that is of highest amount in the solution?(water.)
Procedure 2: What is the basic solution referred to?(5% sodium hydroxide solution) why is referred as a basic solution?(sodium hydroxide is a base)
Procedure 3: here is a dry cell where will you connect the red wire?(positive terminal) how about the black wire?(negative terminal)

  • Assess your student's capability in doing the activity. If you find that your students are not yet ready to be the ones to do this, you are free to make this as a demonstration activity instead.
  • Emphasize the difference in behavior of the two products. In the presence of a flame or spark, hydrogen gives off a "pop" sound while oxygen induces a brighter spark. You may also try to do the same thing with water. Collect some water vapor in a test tube and insert a glowing stick/flame. Nothing is supposed to happen, this will let the students observe that these three exhibits different behavior.

Answers to activity Questions
Q1. A pop sound was heard
Q2. A brighter spark was observe

Construction of an improvised Electrolysis Apparatus
Materials needed
  • Glue
  • Ruler
  • Alcohol lamp
  • Stripping knife
  • Dry cells (1.5 V)
  • 2 Paper clips (bulldog types)
  • 3 Disposable syringes (10 mL)
  • 2 Stainless steel screws #6 (2 X 12)
  • 2 Connecting wires (red and black)
  • GI wire (about 6cm, ordinary wire)
  • Plastic bottle (1L, 8cm in diameter or more) preferably thick and hard
  • Hard plastic straw or dextrose tube(6 cm long)
Procedure
  1. Get two disposable 10 ml syringes and remove the plungers. Attach the two syringes at the base. Using an alcohol lamp, heat the edge of the base to be attached.
  2. Insert each tip of the syringe inside a plastic straw about 6 cm long. Bend the straw to close it and place a bulldog type paper clip to close it and keep it in place. These will serve as the "electrolysis syringes". Construction of an Improvised Electrolysis.
  3. Divide the bottle into 3 portions, mark "cutting lines" around the bottle. The distance between cutting line marks:
    • Bottom portion(3): about 5 cm from the bottom part of the bottle
    • Middle portion(2): about 6 cm from the marked line of the bottom portion(3)
    Heat the stripping knife in an alcohol lamp. Use the hot stripping knife to cut out these line marks.
  4. Use the middle portion of the bottle to make a stand for the simple container maker two small squares measuring about 2cm x 2cm at opposite sides of the base. These will serve as passageways for the cutting wires.
  5. Use the bottom of the bottles as the sample container. Measure the distance between the center of the electrolysis of the syringes. Mark with a line on the bottom of a cup. Then use a hot GI wire(2mm in diameter) bore a small hole at each end of the line. The stainless screws will pass through these holes. Construction of an Improvised apparatus
  6. Insert the stainless steel screws through each hole by rotating it carefully until 1/4 of the nail is out of the bottom of the bottle. To prevent leaks, apply glue around the stainless at the bottom part of the simple container. Note: the glue should only be applied on the outside part of the sample container.
  7. Support the sample container on the stand prepared on #3.
  8. Invert the electrolysis syringes over the stainless screws. Complete the setup. Insert the dry cell to the connecting wires when you are ready to do the electrolysis.

ACTIVITY 2: The periodic table: it's element-ary!

In activity 1, They were able to generate two elements - hydrogen and oxygen. In this activity, They will find out that these two elements are just a fraction of the numerous elements currently existing. Also, that these are the substances that are homogeneous
which are made up of only one component. Being so,they are said to be the "simplest form of matter".
All of the elements are systematically organized in the periodic table. It was described to be "amazingly" done as varied information about all the elements are laid out in a single table. Patterns and trends are evident in the arrangement. It serves and handy reference and as such was labeled as a chemist's tool. This tool then be a good starting material to learn about the different elements. However, note that this is the first time for the students to formally use this tool. Being so, this activity, as it walks them through the periodic table, focuses only with a basic information - name and symbol. Do not overwhelm them with the vast information the periodic can provide. Worse, if they have to memorize its contents. Gradually, let them realize these different information through varied activities that require it's use. In that manner they may find the periodic table not that complicated - it's even quite that it's "elementary".

Reminders
·         Periodic table is a tool in chemistry that we can refer to every now and then. The more we use it, the more we get to be familiar with what it contains. Thus, there is no need to memorize such table.
·         The periodic table is provided at the end page of module 3 and 5. The information placed there is limited to the scope of the module for this quarter. It is highly encouraged to begin with the names and symbols of the elements as they try to know what elements are. Group number will be introduced at the latter part of the activity. Atomic numbers, at this point, will serve as guide on how elements are sequenced in the table; it will be defined as the number of protons of an element's atom. The latter will be discussed in grade 8 when they have already learned the particulate nature of matter.
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