VOL. 26 NO. 1SY 2021-2022

ISSN 0118-9360

MELC-Aligned Science Enrichment

2443 Selya St., Pandacan, ManilaMobile No. 09178713868

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EDITORIAL

Maria Avila Editor in Chief

Anne McCree Editor

Vans Hernan Writer

Dr. Gloria G. Salandanan Publications Consultant

CREATIVE

Drew B. Enriquez Graphic Artist

Marlon B. De Leon Layout Artist

3 did you know?

4 sci-talk

• Chemical Reactions• When Oxygen Meets Others

6 young scientist’s lab

• Effects of Oxygen on Food• Is Brown the Color of Bad?

8 fact file

What Makes a Fire?

10 young scientist’s lab

How to Break the Fire Triangle

12 open page

Forms of Fire

14 soMetHing to do

What Should You Do?

15 sci-quiz

We do not see it, but we cannot live without it. Here are some facts that we need to know about the life-giving element we call oxygen.

If you split open Earth and get to its crust, you will find that almost 50 percent of the elements found there is oxygen. This makes oxygen the most abundant mineral in the crust’s mass.

When humans and animals breathe in, they get oxygen in the air. After this gas enters the lungs, it passes through the lung walls into the blood, which carries it to the cells of the body. From there, it takes part in a chemical reaction called respiration. This process is how the cells receive energy through the in-and-out movement of oxygen and other gases in the lungs.

When you see something burning like this bonfire, oxygen is one of the three things that started it and keeps it going. Burning is another term for combustion.

Outside Earth, oxygen is the third most abundant element after hydrogen and helium (by mass).

What happens if an animal or a plant does not get enough oxygen?

Crust

3

Look at the diagram below. Identify the science concept shown. Write your guess in the box.

Notice how the atoms rearranged themselves and then joined back together in a different way. This is what you call a chemical reaction, a process that occurs when two or more substances are combined to form a new one that has a different identity.

Substances are either chemical elements or compounds.

In a change like this, it is very difficult to get back the substances that you started with, which makes the whole process seem irreversible—although some chemical changes can be reversed, but only by other chemical changes. The starting substances of a chemical reaction are called the reactants, and the new substances formed are called the products.

ExampleSigns of a chemical change

Release of bubbles

Change of color

Production of odor

Release of heat and light

Production of sounds

When a chemical reaction is taking place, there are often signs that can clue you in. You can see a change in color, smell an odor, feel heat, and hear loud sounds. Sometimes, you can also observe bubbles, precipitate, and light. Write an example for each sign of a chemical change.

+

4

Being a highly reactive gas, oxygen is quite attractive to nearly all other elements, readily forming compounds. This process is known as oxidation, the combining of

oxygen with another substance. Many of these compounds formed with this gas are known as oxides. Below are three elements that react with oxygen. Name each element in the left box to complete the name of each compound in the right box.

Mg______________ O _____________

oxide+

C______________ O2 _____________

dioxide+

S______________ O2 _____________

dioxide+

Fe______________ O _____________

oxide+

Oxygen as an atom is written as O.

But oxygen as a molecule is expressed as O2 since it is usually found as a diatomic gas, which consists of two O atoms bound together.

O2 may also be called dioxygen.

5

What you need

What to do

What you have observed

1. What have you noticed in the samples left on the plate?

2. What have you noticed in the samples left in the three containers?

3. What conditions prevented browning the most?

Apple, lettuce, and potato

3 containers Sugar

1. Have the containers ready: Fill the first container with water, the second one with sugar and water (say, 5 g of sugar and 50 ml of water), and the third one with a little lemon juice.

2. Cut up the lettuce, apple, and potato into pieces about 5 centimeters long.3. Leave one sample of each fruit or vegetable on a plate. Then quickly place one sample into each

of the three containers: one into the water, one into the sugar-water solution, and one in the lemon juice.

4. Leave the experiment running for about 1 hour. Observe what happens.5. Answer the questions below.

Water Lemon juice

6

Go back to the experiment and think about the fruits and vegetables on the plate. As you might have observed, those fruit and vegetable samples have all turned brown. This means they have all gone through a process called enzymatic browning. This

chemical reaction, also known as oxidation, takes place when some foods, mostly fruit and vegetables, come into contact with oxygen in the air, causing the food to turn brown.

1This apple has enzymes called phenolase trapped in its cells. These enzymes are special proteins that act

as catalysts, which means they start or speed up a chemical reaction though they are not actually used in the process.

3As the sliced apple begins to brown, it also starts losing some of its nutrients like vitamins C, A, and E, which easily

break down during oxidation. And the longer this fruit is exposed to the process, the lesser the vitamins that it will eventually have.

2Once you slice an apple, you are breaking the skin of a fruit, allowing the phenolase in the apple to react

with the oxygen in the air. This causes a reaction in which the phenolase changes the phenols, the compounds inside the apple, into melanin, which has a brown color.

Based on the given experiment, what substances will prevent or delay the

enzymatic browning longer?

While enzymatic browning may make some fruits and vegetables bad to look at when sliced or cut, it does not necessarily make them harmful to eat. Remember that this process is different from the rotting that comes with the decaying of foods.

7

Label the diagram using the three things that a fire needs for it to burn.

It is a nonmetal gas that is vital for life.

It can be from lightning, the sun, or

another source.

Itcanbeanythingthatisflammableorwillburn.

8

I f you got the answers right, you would have labeled the diagram as oxygen, heat, and fuel, the three things needed for a fire to start and keep going.

These three make up what is called a fire triangle.

This fire model is the simplest way to understand the necessary ingredients to set off the chemical reaction known as combustion or fire. It is also the basic principle that fire fighters rely on to help them manage fires. With this triangle in mind, they know that if one of the three ingredients of fire is removed, a fire will not start or will cease to burn. This makes the fire triangle very useful in fire prevention and firefighting.

In recent years, a fourth ingredient has been added to explain fire. This add-on component is called chain reaction or the actual chemical reaction that needs to happen in order for the fire to start and continue until at least one of the elements of the fire is blocked.

Can you guess what this modified version of the fire model is called? Name and draw it below.

Combustion is the name given to

reactions where a fuel combines with oxygen

to create heat.

9

What you need

What to do

What you have observed

1. What happened to the candle after you did steps 1 and 2? Give the reason why it happened.

2. What happened to the candle after you did steps 3 and 4? Give the reason why it happened.

3. What ingredient in the fire triangle was removed or altered to justify what happened in steps 1 and 2? What about in steps 3 and 4?

Match Short candle Jar

1. Light the short candle and set it on a flat surface.

2. After it is burning well, place the jar upside down over the candle. Observe what happens.

3. Remove the jar and then light the candle again.

4. Take the scissors and cut off the wick below the flame. Observe what happens.

5. Answer the questions below.

Scissors

REMINDER: Ask your parent or an adult to supervise you in this activity.

10

Identify the correct method on how to put out each fire. Then choose the right diagram showing the part of the fire triangle that is removed to stop the combustion process. Write only the letters in the empty colored boxes.

1Metal or electrical fire

Removal

Method

BCover it with sand or a

nonflammable blanket to smother the fire.

3Forest fire

ACut down a line of trees

around the fire to stop the fire from spreading.

2Paper fire

CSpray it with water, which

absorbs the heat from a fire very effectively.

O H F

11

Though they may look the same and may deliver the same devastation if left unattended, fires exist in different forms, with each one requiring a different approach to put it out. And the ways to tackle a fire depend on the kinds of materials that are

involved with or fueling it.

Fires involving solidsFires involving solids, like a cardboard, a piece of furniture, or even the structure of the building itself, are classified as class A fires. For most fires under this class, firefighters use water extinguisher to put them out. Though a popular option for class A fires, water-type extinguishers are never used when the location of the fire is near electrical equipment since water acts a conductor that could intensify the fire further.

Fires involving gasesFor fires that involve gases, the class labels vary depending on the country. In general, gases that fuel this kind of fires are natural gas, LPG, or other types of gases forming a flammable or explosive atmosphere.

Though most fire extinguishers work well with this type of fires, the safest way to deal with it is to shut off the gas supply before using a dry powder extinguisher.

What do you think is the most practicalwaytoreducefirerisksinvolving solids?

12

Fires involving liquidsFires involving liquids, particularly flammable ones, fall under the class B category of fires. Examples of such liquids are cleaning fluids, solvents, fuels, inks, adhesives, and paints, which are often found in offices and workplaces.

Class B fires rarely happen, but when they do, their outcome is more deadly and catastrophic than other types of fire. And the best fire extinguisher to attack a combustion of this nature is the foam or powder variety.

Fires involving metalsIn fires involving metals, which are good conductors of heat, water is not used since it can actually worsen the fire. The favored option used to deal with metal fires is dry powder extinguisher. For small fires of this nature, however, smothering the fire with dry earth or sand is enough.

Fires involving electricityIn fires involving electrical equipment, water is not used because it conducts electricity and can electrocute you. To put out fires of this kind, special techniques and agents are used, most commonly carbon dioxide or dry chemical agents. The carbon-dioxide extinguisher pushes oxygen away from the fire and replaces it with carbon dioxide, which is inflammable and more dense than air.

Whatdoyouthinkisthesimplestwaytoreducefirerisksinvolvingliquids?

What observable signs help tell you that the combustion process is taking place?

ItisimportanttonotethatfireclassificationisgenerallylabeledA,B,C,D,E,andsoondependingonthespecificmaterialsinvolved.Thisclassificationslightly varies from country to country. In the United Kingdom, for example, itsClassCfiresinvolvinggasesonlymaymeanClassBfires,whichcombinesbothflammableliquidsandgases,inthePhilippines.

13

Analyze the photo below. Tell what kind of fire situation is shown. Then on a sheet of paper, list the steps that should be done to deal with this kind of fire.

Whatliquidshouldyouneveruseforthiskindoffire?

14

1. What is another word for chemical reaction? a. Chemical redoxb. Chemical changec. Chemical transfer

2. What happens if an animal or a plant does not get enough oxygen?a. It will adapt and take in other

gases for it to survive.b. It will get tired.c. It will not be able to respire and

will die.

3. For combustion to start, which three things must be present? a. Carbon dioxide, oxygen, and

smokeb. Oxygen, heat, and fuelc. Match, candle, and smoke

4. Which chemical reaction can cause a sliced fruit to brown?a. Respirationb. Oxidationc. Conservation

5. Which chemical reaction will occur when oxygen, heat, and fuel are present and the conditions are right?a. Combustionb. Reductionc. Decomposition

1. Combustion happens all the time in every living thing.

2. Oxidation reactions occur in food and nonfood items.

3. A catalyst is a substance that speeds up the chemical reaction without being changed by the reaction itself.

4. A substance formed in a multiplication reaction is called a product.

5. Reactants are the substances present at the start of a chemical reaction.

6. Water should always be used on electrical fires due to the risk of electrical shock.

7. Water is never used on office fires as oil and water do not mix, meaning the water only makes the oil form smaller droplets, making the fire even worse.

8. A useful method of removing heat from a fire is to use water, which absorbs the heat from a fire very effectively.

9. You can control or stop a fire by controlling the amount of the fuel available, the amount of oxygen available, or the source of heat.

10. Blowing out the flame on a candle is a good example of removing oxygen from a fire triangle.

IIII Write T for true. If false, write the correct word or phrase that should replace the underlined one.

II Underline the correct answer.

15

Guess the mystery photo.