MY SCIENCE PUSHCART

RISE AND FALL OF STARS

2011-06-06T11:20:00.000-07:00

Physics is so dear to me, although many students and science teachers alike do not feel good with it. To some, it is boring and full of Maths. Others just do not find it attractive to their intellect, I should say. But to me, it is full of wonders and an endless chain of discoveries. One of my favourite topics in this field is Space and the Universe. It appeals to me differently because I feel like watching a movie and doing some reflection at the same time.

Just like the stars that we glimpse in the sky on quite nights, they are full of excitement. They are part of the history that unfolds before our senses, because the stars that you see were actually there many years ago. Stars are light years away from the Earth, and so it would take years for its emitted light to reach us. A light year is a distance that light can travel in one year. If a ray of light travels in a vacuum in approximately 3x10⁸ m/s, the ray of the sun which distance from the Earth is approximately 150 million kilometres could reach the Earth in eight minutes, how much more for distant stars?

They are simply stars, but it is fascinating to learn that they have a life cycle. And the process is extremely long, explosive, but amazing. Like us, they are born, they live, and will eventually die.

THE BIRTH

The theory is that the birth of the star begins after the Big Bang. This tremendous explosion produced a massive cloud of gas and dust particles. Much of these huge clouds are NEBULAE. Gravity plays a very significant role to gradually pull this gas and dust particles together creating a denser ball of gas in the cloud. They grow in size over time and form a core over millions of years. As it gets larger and larger, the core temperature increases incredibly, and the pressure mounting so high, producing an intense brightness and eventually becomes white hot. Most of its energy stay trapped inside whilst some are emitted as infra red radiation. The ball of gas begins to look like a massive dark red glow hanging in space. For another millions of years the mass of the gas changes and a star is slowly coming into life. This is now called a PROTOSTAR.

The protostar continues to be unstable due to nuclear reactions within. For another series of changes, the very hot core produces a violent flow of particles scattering outwards blowing away gas and dust in the banks of cloud around. Slowly the core collapses, and nuclear fission starts releasing enormous amount of energy. As temperature further increases, the mass of the REAL STAR begins to emerge.

ITS LIFE

The sun in our solar system is a star and it has its life like any other stars in the universe. Our very own sun is nearly 5 billion years old and is believed to be in its midlife. There is really no serious reason to fear about it dying, because it would still take billions of years and this generation of humanity and surely hundred more generations could still enjoy the benefit of its life. Hydrogen fuel as a main gas component of stars is responsible for its life. However, a star continues to lose mass in the form of energy like how Albert Einstein predicted in his familiar energy equation. As its mass decreases so as its gravitational power, and this causes the instability of the inner radiation pressure and the pull of gravity. But, for as long as there is enough of this hydrogen fuel, the star continues to shine and provide us bright nights of diamond-like glitters.

THE DEATH

That is true, stars will die eventually. Depending on the size of the star, two possibilities would happen. It may either become a black dwarf or a black hole. Our very own sun is a medium-sized star which after millions of years, all its hydrogen fuel would run out. The mass of the sun would decrease and so the inner radiation pressure would become higher than the gravity. The effect would lead the star to expand and becomes a red giant. As it expands, the core temperature decreases then as it cools down the red giant would sooner or later contract. As the pressure decreases, the gravity gets the upper hand to pull back the red giant into itself and after many more years, it would collapse into a so called white dwarf. And as it cools further, the hot white dwarf becomes a black dwarf. For very massive stars, they do have a more interesting death. Yes, the hydrogen fuel be all used up and its gradually becomes a red supergiant, it cools down, quickly contracts and collapses, making its core very dense. This speedy contraction, with a very high gravity increases the temperature to unimaginable level.

Finally, the star would explode to what is called SUPERNOVA, releasing an enormous amount of energy. Aside from blasting off massive surface layers, some elements are formed at this explosion. A neutron star would emerge which turns into pulsar, and if it has enough mass, its gravity would crumple it still further to become a black hole.

ROCKS OF THE EARTH

2011-05-24T12:25:00.000-07:00

Materials like chairs, woods, carpets, clothes, glass, metals amongst others; are materials found in or on the Earth. Chemical reactions helped manufacturers to make these raw materials become useful, attractive, and durable. The earth’s crust provides abundant amount of minerals, rocks, and fossil fuels. A mineral is a single substance, which has a chemical name and formula. A rock is a mixture of different minerals. Examples of minerals are limestone and rock salts. Their purest from are called calcium carbonate (CaCo3) and Sodium Chloride ( NaCl), respectively.

It is believed that when the Earth cooled down millions of years after the birth of the solar system, its molten crust solidified into igneous rocks. Over millions of years, the geological
changes that took place in the life of the Earth, other types of rocks were created that include sedimentary and metamorphic rocks.

Have a look at these rock photos that I personally took some weeks back.

FRUITY DNA EXPERIMENT

2011-05-20T10:05:00.000-07:00

Cells are composed of nuclei, and nucleus is considered the largest single structure within the cell. It is further composed of separate structures called chromosomes which are responsible to carry information for reproduction or for sort of genetic analysis in laboratories. These chromosomes are made of a more complex polymer called DNA or Deoxyribonucleic acid. Although DNA is a very large molecule, you could not see it with your naked eye, unless you know and you have a great deal with it.

The Fruity DNA experiment will teach you the procedure how to collect large number of chromosomes using common fruits. This is just a simple laboratory experiment for a biology class.

Materials/Equipment

4 x 100ml beaker
2 x 250ml beaker
1 x 500ml beaker

stop watch
fruits (preferably fruits that are slurry when crushed like KIWI, or tomato, or strawberry)
filter paper
plastic funnel
4.0 grams sodium chloride (common salt, fine ones)
measuring cylinders
pestle and mortar
washing-up liquid
stirring rod (preferably glass)
kettle
ice in a plastic bowl
wire hook (#22 )
goggles
ethanol (make sure it is inside the freezer over night and before using)

Note: Peel the fruit and slice into smaller dices. Allow the kettle to boil before you start the procedures. Try this first before introducing to your students, and in my experiments, I find it best to put more ethanol into the mixture.

Procedure:
1. Weigh 4.0 grams of common salt and put into the 250ml beaker.
2. Add 15ml of washing-up into the same beaker and stir thoroughly to make sure the salt is dissolved completely. Then put this mixture to one side.
3. Crush the fruit using the mortar and pestle until it becomes mushy and ‘slurry’, put this in another 250ml beaker.
4. Add an equal volume of the mixture you made in procedure 2 to the mashed up fruit in procedure 3.
5. Put hot water into the 500ml beaker and place the whole beaker you prepared in procedure 4. (If water bath is available, set it at 60 degrees)
6. Leave this to stand for the next 10 to 15 minutes.
7. Prepare the filter funnel and the filter paper, when 10 to 15 minutes has elapsed, filter the mixture and collect the filtrate using the 100ml beaker. You should have a pure liquid into the 100ml beaker.
8. Hold the beaker properly and tilt it slightly, very slowly put as much as you have filtrate the ice cold ethanol down the side of the beaker.
9. Do not stir, leave it to settle for a minute. You should be able to see some layer between the ethanol and the filtrate. This is the fruit DNA, and if possible, use the wire hook to pick up some of it.

Guide Questions:

What’s the use of ETHANOL?
Why do you need to mash up the fruit?
What’s the washing-up liquid for?
What is the role of sodium chloride?

SIMPLY FACTS

2011-05-19T12:38:00.000-07:00

Although plants do not have nerves, they do use electrical impulses for coordination. These impulses are like the humans, but much slower. The Venus flytrap plant is a good example.
A single photon of light – the smallest quantity you can get, is enough to stimulate a rod cell.
Each off your fingers has about 3000 touch receptors. This is as many as the whole of your back and chest.
You can survive for weeks without food, but only a few days without water
A healthy man should have about 15% of his weight as body fat. A healthy woman should have about 25 %.
Alcohol gets from the stomach to the brain in just few minutes.
The heat inside the Earth is produced when radioactive substances called isotopes decay. It is not heat left over from when the Earth first formed.
One strand of optical fibre can handle up to 10000 telephone conversations all at the same time.
The reason stars seem to twinkle is because the atmosphere distorts the light reaching our eyes. Out in space stars give a steady, clear light.
Our sun is a middle-aged star. It is about 4600 million years old. It burns about 4 million tonnes of hydrogen every second.
Comets come from deep space. As they get closer to the Sun they develop a tail of dust and ionized gas. The tail always points away from the sun, even when it moves away back into deep space.
Our sun and solar system are only 4.6 billion years old. That means that our part of the Universe has probably gone through the birth, life, and death cycle at least three times already.
Dark matter does not emit any electromagnetic radiation and therefore it cannot be seen by any of our telescopes. It is thought that 85% of the Universe could be dark matter.
A drop of your blood contains about 5 million red blood cells.
During an average life a heart beats over 2 500 000 000 times and pumps 340 million liters of blood.
Bats can disconnect the bones in their ears while they send out their ultrasound squeaks, so that they don’t deafen themselves.

CHEMICAL CHANGES

2011-05-18T09:48:00.000-07:00

One of the most important topics in Chemistry is chemical changes. Students find it interesting because they get what they see; and learning is enhanced when they love what they are doing.

Teachers and students alike could try this simple yet relevant activity for chemical changes. It is always recommended that teachers are around to supervise when students are allowed to do this practical.

Theory:

There are signs if chemical change has taken place. When one or more substances are formed out of a reaction then chemical change has occurred. In chemical change, the change is usually difficult to reverse. For example, when you cook food, chemical change happens and there is no way you could get back the original substance if you wish to. In chemical change, energy is taken out or given in. Just like, when iron reacts with sulphur; heat is produced. When there is a chemical reaction, the atoms are rearranged so they mixed in an entirely different way.

Materials/Equipment/Solutions

Lead nitrate solution

potassium iodide

Barium chloride

Sulphuric acid

Hydrogen peroxide ( 15 % solution)

Hydrochloric acid

Manganese oxide (test powder)

Copper carbonate

Test tubes

Wooden splints

Spatula/laboratory spoon

Note: All solutions must be diluted to 0.1M unless specified otherwise.

Precipitation Activity

Get one test tube and half-fill it with dilute lead nitrate. Half-fill another test tube with dilute potassium iodide. Pour one solution into the other. Put the test tube with the mixture in a test tube rack and observe what happens. Is it a chemical change? WHY? Wait for 10 minutes and record any observations.

With new set of test tubes, prepare the same amount as in procedure 1 the dilute solutions of barium chloride and sulphuric acid. Pour one into the other. Is it a chemical change? Explain.

Fizzing Activity

Prepare a quarter of hydrogen peroxide into a test tube. Get a wooden splint and dip into the manganese oxide. Now dip the splint into the test tube with hydrogen peroxide and put your thumb to cover the test tube’s opening. What do you observe? What can you feel?
Half-fill a new test tube placed on the test tube rack with dilute hydrochloric acid and put a spatula of copper carbonate into the solution. Record any observations.

HOW TO DILUTE HYDROCHLORIC ACID (HCl)

2011-05-17T11:58:00.000-07:00

The instructions below are only good for concentrated Hydrochloric from

35-38% solution with a specific gravity of 1.18 and a molar mass of 36.46 g/mol.

The concentration of Hydrochloric acid decreases over a long period of time; as the gas diffuses into the atmosphere. It is advisable to keep stocks in secured glass containers and should be kept properly inside the laboratory. It is best to store them in an outside stock room if there is any in your school.

Do not attempt diluting Hydrochloric acid if it is your first. Ask a colleague or from a more experienced laboratory staff to help you. Do not allow students to dilute concentrated solutions, but you can demonstrate this in the science laboratory in order for them to understand the procedure correctly. However, you may ask them to dilute further diluted solution from 1M and lower.

Instructions:

Wear gloves and goggles
Ideally, use fume cupboard if it is available in your laboratory.
Measure the required volume of concentrated HCl in a measuring cylinder. ( Consider the table below.
Add this to about two-thirds of the final volume of water in a separate beaker.
Stir the solution properly.
Transfer the solution into a larger measuring cylinder and add water to the required level.
Mix thoroughly. And it’s done.

The best way is to make large amount of 2M and dilute it further to lower concentration as in the table below.

GUIDE TABLE

Required Diluted Concentration	Required Volume of Solution
	500 ml	1000 ml	2500 ml
2 M	84 ml	167 ml	417 ml
1 M	42 ml	84 ml	209 ml
0.5 M	21 ml	42 ml	105 ml
0.4 M	17 ml	34 ml	84 ml
0.1 M	TEN-FOLD of 1.0 M solution
0.01 M	TEN-FOLD of 0.1 M solution

FERMENTATION ACTIVITY

2011-05-15T12:39:00.000-07:00

This practical can be done as a demo or class experiment provided you have enough materials for the whole class.

Fermentation is the process of breaking down of food by micro-organisms using anaerobic respiration. Yeast is a single-celled fungus, and reproduces by growing buds out of the cell and feeds itself on sugars like glucose. In the process of fermentation, the yeast makes alcohol (Ethanol) and carbon dioxide. To illustrate it better, consider the equation below

The Equation:

GLUCOSE --> ETHANOL + CARBON DIOXIDE

Materials/Equipment
• boiling tubes / (you may use conical flask)
• boiling tube bung and delivery tube
• yeast
• sugar
• 1000ml beaker
• 100ml beaker
• limewater
• test tube

Procedure:
a. Using the 100ml beaker, put a spoonful of yeast and sugar, and add 50ml of warm water ( not boiling water, otherwise it would kill the organism)
b. Mix them properly until the yeast and sugar are dissolved.
c. Pour enough amount of the mixture into the boiling tube.
d. Put the bung and delivery tube and run this into the test tube with limewater.
e. Observe the colour of the limewater. It should turn cloudy due to carbon dioxide that is given off by the mixture.

NOTE: It is more exciting to collect the carbon dioxide using balloons. It is preferable to use conical flask instead of the boiling tube. Increase the amount of the mixture and put it in the conical flask. Collect the carbon dioxide by putting on the balloon at the opening and wait for 20-30 minutes to see the balloon slowly starting to inflate. You can leave it for few hours but not overnight. It may burst out and will surely create a mess. The mixture has an odd smell.

AN ENDLESS SCIENCE

2011-05-08T10:32:00.000-07:00

Are you still struggling to reconcile the disparity between Darwin’s evolution theory and the Divine Creation? Perhaps most of us are recurrently, mystified about the feasibility of time travel and time machines. How about the existence of parallel universes, do you find it amazing or rather irrational? Still interested around alien invasion or you may be more engrossed reflecting the issues of global warming and its menace that we are already living through. Plus, the revolution of technology that has affected every single aspect of our life, we may continue to ask these questions: Why do we have to learn Science? Is there an end to Science?

I am always amazed with Science, and the practical experiences that I learned in school were so rewarding up to this time. But there are volumes of concept in science that could not just be done in the classroom, and could not even be observed by means of simple equipment and experiments. Things that go beyond common sense. More often than not, we are stuck with questions hanging round the brain and only content ourselves with the explanation provided in books and excellent scientific journals. It should be all right then, for these scientists and authors have studied tremendously on these subjects, and thus afforded us a truly credible description on every possible question there is in science. You could not do a classroom practical about Big Bang theory, could you?

Science is an endless spectrum of possibilities. Much have been discovered through it, yet these are nothing compared to the even bigger space that remained hidden and unexplored. Science is life itself that extends through time and space, and accordingly, the more we know about science, the more we realize how little is our knowledge about it.

Practically, science is everything. But don’t get me wrong about this notion. I do not propose to disregard the ultimate being who I faithfully believed created this universe and beyond. What I am trying to say is that, science is a perfect work of creation that has come about through a perfect mind. A creator so intelligent and infallible, that everything is put in apposite order and beginning, yet so complex to the human intellect. I may have that immense passion for science, but it does not, in so many words, terrorize my faith to one Supreme being, who gave us this world to live and explore.

What makes science so intriguing to me is that it has the facility to answer many questions and the method to make use of simple things around, become so relevant and useful to mankind. For example, the discovery of electricity is one of the greatest achievements of science, and thousand more discoveries were made because of it. The development of technology could not have been so massive if it were not of science. According to Jacob Aron, a young mathematician turned science writer; ‘ Without science, you would not be reading this. Without science, there would be no computers, no internet, and no blogging.’

Could science end somewhere, no one knows. What scientists do know is that there are still loads in store for people to know in this universe, and our generation could not utterly discover all these.

All the same, science has definitely influence our way of thinking, in the manner we understand the universe and the things in it. We are greatly benefited by its development and we continue to learn more to make life better.

LET’S BURN YOUR MONEY

2011-03-07T14:38:00.000-08:00

What? That sounds insane, but remember there is a load of crazy stuff in science that we can learn and enjoy from. I do not mean burning your money is fun, neither I would give in to the challenge if I am not confident I could actually have it back in exactly the same condition as it should be. You can practice this using ordinary white paper or filter paper cut into note-like sizes, that is to build up your confidence that it truly works. So, have fun and burn your money away.

Burning money is intended for demonstration purposes to simply stimulate students’ interest towards the topic COMBUSTION. It is expected that you will observe the necessary safety precautions in doing this although there are no reported cases of accidents related to it so far. (I don’t want you to be the first!).

You need:

Goggles
mixture of ethanol and water
Heat mat
3 x 400ml beaker

paper/filter paper or real note

pair of tongs

ethanol (This is flammable, so be careful)

water

sodium chloride (common salt)

balance

Procedure:

Cut out three absorbent paper/filter paper into desired size
Prepare the three beakers with labels B1, B2, and B3.
Put 100 ml of water in B1.
Put 100 ml of ethanol in B2.
Put a mixture of 50ml water and 50ml ethanol in B3. Add about 3g of salt and stir slowly until dissolved.
Prepare the Bunsen burner and put it on the heat mat. Before you light it, make sure it is at a safer distance from the 3 beakers.
Using the tongs, soak one piece of filter paper in B1 and allow it to drain. Burn it by moving unto the yellow flame of the burner for few seconds. Expectedly, it does not burn because it’s wet.
Try another piece of filter paper and soak it into B2 and allow to drain. It will surely burn easily because of the ethanol.
Finally, do the same procedure above to the third piece of filter paper but soak it into B3. This time the alcohol ignites and you will notice it burning, however the paper does not burn away because the paper will still be wet with water but the alcohol has burnt away.
If you are confident enough, try it with a real money. Have fun!

COLOURFUL CRYSTAL GARDEN

2011-03-07T14:11:00.000-08:00

Recently, I talked about demonstrating firework effects using common salt compounds available in our chemistry laboratory. These compounds can also be used to make other exciting science activities like the COLOURFUL CRYSTAL GARDEN.

This is a simple, but exciting practical/demo that teachers can do in the laboratory. Again, just be careful with the salt compounds for they maybe corrosive, irritant, or toxic.

Before you start, you need to secure the following things:

SODIUM SILICATE ( commonly called WATER GLASS)

WATER

SALT COMPOUNDS

nickel nitrate
calcium chloride
lead nitrate
copper sulphate
manganese chloride
cobalt chloride
iron chloride

GLASS JAR (preferably with LID)

100 ml BEAKER

GLASS ROD

WHITE FINE SAND

SPATULA

Procedure

Measure out 100ml of sodium silicate using the beaker, and pour it carefully into the glass jar. Wash the beaker right away.
Add 400ml of water to reduce the concentration and stir it thoroughly using a glass rod.
Put a layer of white fine sand and wait until all the particles settle down the bottom of the jar.
Slowly, using the spatula tip different coloured salt into the mixture and wait them start to grow into a beautiful crystal garden.
The reaction depends upon the concentration of the mixture. The higher the concentration, the faster the reaction of the compounds.

HYDROGEN BALLOON

2011-03-05T14:33:00.000-08:00

Let us get some basic stuff together and make a hydrogen balloon to demonstrate in the class. The main idea is to collect hydrogen gas from an acid-metal reaction and show the students the safest way to do it.

You need:

2M sulphuric acid

zinc granules

two pieces of rubber balloons

conical flask.

We will use the 2M sulphuric acid because the higher the concentration, the faster the reaction and the more gas we can collect. Just be very careful about the corrosive nature of the acid, it can cause skin irritation or burns. Use rubber hand gloves if available.

Procedure:

Put a spoonful of zinc granules into the conical flask.
Slowly pour 50ml of 2M sulphuric acid in it. The reaction takes place immediately.
Use the rubber balloon to collect the gas as shown in the picture below.
If you have collected enough hydrogen, take the balloon off and tie its end properly.
You can collect more gas as long as the reaction is going on.

Note:

To test the hydrogen balloon, you need an iron stand and clamp to hold it. Prepare a stick at least one meter long and attach/tape a wooden splint on one end. Light the splint and put it under the balloon. It would burst out with a considerable bang.

Warning: Please ask the kids to stay away while you pop up the balloon and remind them to cover their ears.

CHEAPER LAVA LAMP

2011-03-03T14:27:00.000-08:00

As much as possible, science teachers would want to do activities in the class, which are exciting but less expensive. Especially when the kids are asked to bring the materials needed and turned out to be difficult to find or too much for the wallet, the thrill to do it would eventually fade.

There are many lava lamps available in the market but why not make your own and use of materials that one can easily grab in the cupboard or take out from the medicine drawer or buy from the nearest supermarket. Today I am sharing to you how to make a LAVA LAMP which I have done myself several times in science club activities or classroom demonstrations.

This activity can be conducted in a secondary class or entry level in college as a demonstration. There is in fact no pre requisite knowledge to do this but common sense always takes part in science experiment to appreciate the result. But it is intelligible and challenging to start mapping concepts:

What happens when you mix oil and water?

What happens when you put a drop of food colouring into the mixture?

What happens when you put an antacid into the mixture of water and oil?

Materials Needed:

Small plastic bottle with cap

Vegetable oil

Food dye/colouring

Antacid (ex: Alka-Seltzer)

Water

Paper towel

Bucket

Procedure

1.Measure about 200ml of vegetable oil and pour into the plastic bottle.

2.Fill the remaining space of the bottle with water.

3.Add small amount of food colouring to give the water a darker shade.

4.Break up one antacid tablet into tiny pieces.

5.Drop bits of antacids into the mixture of oil and water and observe what happens.

When the bubble stops, continue to add more bits of antacid.

6. When you are done putting all the antacids and the reaction has stopped, screw on the bottle cap.

7. Tip the plastic bottle back and forth and watch what happens. The tiny drops of liquid would join together and produce a big lava lamp ball.

Theory:

Oil and water molecules do not mix. When the water is poured into a plastic bottle with the oil, the water would descend to the bottom because water is heavier than oil.(oil is less dense than water). Not even if you insist to shake it up thoroughly. We call it immiscible – they don’t dissolve in each other.

The oil might break up into small drops, but it does not mix with the water. However, the food dye will mix with the water. On the other hand, the antacid reacts with water to form tiny bubbles of carbon dioxide. These bubbles attach themselves to the beads of coloured water and cause them to float to the surface. When this bubbles break up, the drops of coloured water settle back to the bottom of the bottle.

MAKING and TESTING ELECTROMAGNETS

2011-03-01T14:20:00.000-08:00

There is a very practical and simple way to make and test electromagnets in science laboratory. After you are done discussing the theory of electromagnets, it is time to allow students some hands-on activities, to thoughtfully remember the concept. This is not a grand experiment though, but at least your high school students could look into how and what are the necessary materials needed to make a simple electromagnet, and test its strength afterwards.

Theory:

An electromagnet is a magnet made using electricity, thus it is only magnetic when there is electric current passing through the coil of wire. The direction of the north and south poles of an electromagnet depends on which way the current is flowing through the wires. You can increase the strength of an electromagnet by:

increasing the number of coils
increasing the current in the wire
using a magnetic material for the core

So, make sure the materials below are all available and ready when you do this experiment in your science laboratory. Although this can be done individually, it is always better to do laboratory practicals in group to make sure the process could become interactive too amongst the group members.

You are going to make 5 electromagnets of different strengths, and in this practical vary the number of coils around the iron core.

Materials:

Insulated wire for each group, at least 5 meters

connecting wires

alligator clips/crocodile clips

variable power supply (preferably 0v-15v range, DC)

small nails, paper clips (to test the strength of the electromagnet)

5-inch iron rod (at least 1 cm diameter, large nails could be a substitute)

MAKING

To start with, make an electromagnet with 10 coils by winding an insulated wire around the iron core. Make sure you leave at least 5cm of wire to both ends to connect the power supply later on in the testing.

Put it aside, and make 4 more electromagnets with 30, 40, 60, and 80 coils.

TESTING

To test the strength of your electromagnets, make a circuit connecting your electromagnet to a 6.0V power supply. You may also connect a galvanometer or milliammeter in series to your load, to check the current.

Put small nails on the table and pick them up using your electromagnet. Count the number of nails it is able to hold.

Record it in the suggested table below:

No. of coils	Number of Nails
10
30
40
60
80

Test the other electromagnets and record your results in the table.

Note: You must ask the kids to make their own conclusions. Let them suggest another method to increase the strength of the electromagnet. On the analysis part, ask them to graph results and let them identify the dependent and independent variables of the experiment.

HIGH tide and LOW tide AGAIN?

2011-02-25T14:13:00.000-08:00

Many students would still find it confusing to understand the phenomenon of high tide and low tide. What causes it and why?

Simple reason is to associate it to gravity of the Earth and the Moon, and the pull of force is called gravitational force. Gravitational force exists between two objects with mass. For smaller objects, this force is not very noticeable. However, for massive objects like the planets, this gravitational force creates a significant effect. Both the Earth and the moon exert a force towards each other. The gravitational force decreases with increasing distance, so the water nearest the moon is pulled more strongly towards the moon than the mass of the Earth itself. This force causes the water of the earth to swell on the area directly opposite the moon –which is called HIGH TIDE.

But this effect is symmetrical, which means it is also high tide on the opposite side of the Earth. (It is easier to imagine a rounded balloon, that when you press it in the middle, the two opposing sides are both going to bulge out, but in the case of the Earth and the moon, it is the pull of gravity that creates this bulge). The earth and the moon are also revolving around a common center of mass, causing the oceans to be ‘flung outwards’. If there ever is a vast body of water on the moon’s surface, it would also experience high tide and low tide like the earth.

FIREWORKS AT WORK

2011-02-20T14:09:00.000-08:00

There is a more interesting activity to explain how fireworks are made, without actually exposing the students to greater risk. ( I have to say greater because there is still a risk doing this practical.) How do fireworks create that spectacular fountain of colours and amazed young and old alike. The gorgeous exploding mixture of purples and reds, blues, yellows, greens, lilac, is just a salt away. Chemistry has loads to offer when it comes to interesting activities, and this is one of those.

Sparklers and fireworks contain metal compounds. These compounds give them the different colours that you see in firework displays. Prepare some of the following metal compounds and try it first before you do this activity in the laboratory. Also, soak wooden splints in a beaker.

The salts are listed below and opposite are the corresponding colours it gives.

Magnesium bright white

Sodium salts yellow

Copper(II) chloride turquoise

Lithium carbonate red

Barium carbonated green

Lead nitrate lilac

Using the wet end of the wooden splint, dip it into the powder/salt and place it unto the blue part of the Bunsen burner flame. Observe the different colours produced by different compounds.

Note: You can also try testing solutions out of the same compounds.

SIMPLE EXPERIMENT: LAW OF REFLECTION

2011-02-15T14:05:00.000-08:00

This activity investigates the rule of reflection, which focuses on obtaining, collecting, and considering evidence. The students should learn and remember the basic terms that are associated with the law of reflection.

When you look in a mirror, you can see a reflection of yourself. If you look at texts on the newspapers or magazines, they appear to be reversed, which is the way light is reflected by a mirror. How can we investigate this phenomenon? What is reflection? What is the law of reflection?

In this practical, you need plane mirrors, concave, and convex mirrors. Your focus is on making measurements accurately, recording the results, and making conclusions from the evidence collected.

Materials/Apparatus

ray box
dc-power supply (depending on the ray box)
slit plate
plane mirror
concave mirror
convex mirror
a piece of white paper
sharp pencil
ruler
protractor

Procedure

Place the white paper on the desk or table.
Put a plane, concave, or convex mirror along one of the short edges.
Using your pencil, draw a line on the paper along the front of the mirror.
Place the protractor in front of the mirror.
Draw a dotted line from the mirror at 90 degrees. This is your ‘Normal Line’.
Turn on the ray box with the single slit inserted, and aim the ray at the point where the normal line touches the mirror. ( This is the incident ray).
Measure the angle between the normal line and the incident ray.
Keeping the set-up in exactly the same place, measure the angle between the reflected ray and the normal line.
Repeat procedures a to h using four more different incident angles and measure their reflected angles.
Draw a table for your results.

Assessment

Describe the pattern in your results using appropriate science words.
State your conclusion based on the evidence collected.
Explain your conclusion using scientific knowledge and understanding.

CONDUCTION, CONVECTION, and RADIATION

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Many practical classroom activities could be carried out, when teaching the concepts of conduction, convection, and radiation. These are simple yet relevant, and would allow students to understand the topic easily. The concept has to be taught in the first 15 minutes of the 1-hour class and then proceed to show some of these demos.

The teacher prepares the materials needed and see to it that safety precautions are observed.

CONDUCTION ACTIVITY

Prepare three different rods such copper, glass, and iron (or whatever is readily available, except of course plastic rods).
Place them on a tripod and fix a small nail near one end of each rod using candle wax or Vaseline as ‘glue’. (Make sure the rods are not touching each other).
Using a bunsen burner, heat the other ends of the rods evenly.
Record the time it takes for each nail to drop off from the respective rods?

Observation

What happens after few minutes?

How many minutes does it take for the three nails to drop off?

Make a conclusion based on your observation and evidences.

CONVECTION ACTIVITY

Put a beaker of water on a tripod.
Prepare two pieces of potassium permanganate crystals.
Using a drinking straw, drop the potassium permanganate crystal into the beaker of water, near to the side.
With the Bunsen burner ready, warm the water near the crystal with a small Bunsen flame.

Observation

What happens to the crystal and the water?

What have you notice with the movement of the convection current in the

water?

RADIATION ACTIVITY

Prepare two cans of equal size (with lid and a hole for the thermometer), one is polished and shiny on the outside and one is black and dull. ( You may use aluminium cans, paint the other one to make it black and dull)

Suggestion: It would be good too, to use boiling tubes with rubber bung and thermometer. One boiling tube is wrapped with aluminium foil, the other one wrapped with black paper.

Put a thermometer in each and tip equal amounts of hot water.
Let them cool, side by side.
Stir regularly and record their temperatures every minute.

Observation

What do you observe with their temperatures?

Which cools down more quickly?

Which can, is losing energy quicker?

Which is a good absorber of radiation?

Concept:

Objects take in and give out energy in the form of radiation all the time.

Different objects transfer different amounts of radiation, depending on their temperature and their surface. A dull black surface loses energy more rapidly and therefore it is good radiator. On the other hand, a brightly polished surfaces do not lose much energy by radiation, they are called poor radiator.

TRY THIS OUT!

For conduction: Prepare a boiling tube with three-fourths water. Tilt it a little and hold it at the bottom. Aim a slow Bunsen flame just below the water surface until the water boils at the top.

Concept:

Most liquids are poor conductor of heat. The water might be boiling at the surface but it could not warm up the liquid down below.

2. For convection: You may show convection current through smoke

movement using a chimney box ( if available in your school).

3. For convection: Draw a spiral on a paper. Cut it out and hang it from a

string or cotton thread. Use it to investigate convection currents by

placing a lighted candle near the bottom.

USEFUL INFRA-RED

2011-02-08T14:02:00.000-08:00

The sun is a primary source of the Earth’s energy. In fact, the energy to heat us up travels from it at the speed of light, just like the light rays. This particular energy rays that cause the most heating are called infra-red rays. These are also light rays but of longer wavelength. Since it is a light ray, it can also be reflected by mirrors. This is where the idea of ‘solar furnace’ comes about, particularly in hotter parts of the world where solar furnace is used, to collect the rays from the sun and focus them on to kettles or cooking pans.

Activity

On a sunny day, take a concave mirror outside to heat a spoonful of water.

Take the same concave mirror outside to light a match. It would help better if you first blacken the head of the match with a pencil.

Note:

Be very careful in conducting this practical.

HOW TO COLLECT and TEST OXYGEN, HYDROGEN, and CARBON DIOXIDE

2011-02-05T14:23:00.000-08:00

One of the most challenging tasks of a science teacher in a chemistry class is how to show that gases exist and it can be collected from simple reactions. Most common amongst these gases are OXYGEN, HYDROGEN, and CARBON DIOXIDE.

Yet there is a simple activity that could be done as a demo or class experiment to confirm those scientific explanation about acid-metal reaction. Be sure the materials are readily available in your laboratory. There are other processes to produce these gases but these are the ones helpful and practical in a school setting.

COLECTING AND TESTING HYDROGEN GAS

There are few ways to collect hydrogen gas and test it. But the most exciting amongst these, is to collect it into a balloon and pop it afterwards.

You need a regular size conical flask, zinc chips/zinc granules, and 2M sulphuric acid. Be very careful of the corrosive nature of acids. 2M sulphuric acid may irritate or burn your skin.

Procedure:

Put reasonable amount of zinc granules (10-15 chips) into the conical flask. Add 20 ml of sulphuric acid. The reaction takes place right away, cover the flask with the balloon and wait for at least 5 minutes. As gas is produced from the reaction, the balloon would slowly inflate, the gas being trapped inside the balloon is a hydrogen gas. Consider the chemical equation below:

Zinc + sulphuric acid --> zinc sulphate + hydrogen

Hydrogen gas can also be produced with the reaction of magnesium and hydrochloric acid. If these materials are available in your science laboratory, you may try it as well.

Magnesium + hydrochloric acid --> magnesium chloride + hydrogen

Testing:

Warning: Please ask the kids to stay away while you pop the balloon and remind them to cover their ears slightly.

Collecting and Testing Oxygen Gas

Combustion is another term for burning and it happens when substances react with oxygen in air. Oxygen is needed for burning. Fuels burn faster in pure oxygen than in air. Manganese (IV) oxide catalyses the decomposition of hydrogen peroxide to form water and oxygen. Refer to the chemical equation below:

Hydrogen peroxide + manganese oxide --> water + oxygen

Procedure:

Pour 10ml of hydrogen peroxide into a test tube. Take a spatula of manganese oxide and tip it into the test tube. It would start to fizz and if you cover the tube tightly with your thumb, you would feel the oxygen gas trying to escape from the tube.

Testing:

If a smouldering wooden splint is put into the test tube of reacting hydrogen peroxide and manganese oxide, but not touching the solution, the splint will burst into flame.

Collecting and Testing Carbon Dioxide

Carbon Dioxide is an odourless, colourless, and tasteless gas, which is stable, inert and non-toxic in nature. The simplest way to collect carbon dioxide is by reacting calcium carbonate with hydrochloric acid. For classroom demos, you only need a small amount of Hydrochloric acid, which is diluted to 1M. ( 2M concentration works best but should be used with extra care).

Procedure:

Put 20ml of HCl into a conical flask. Add a spoonful of calcium carbonate (or limestone chips) to the HCL. When the reaction starts, cover the conical flask with a bung and delivery tube so that you can collect the gas through the delivery tube and into an upturned test tube. (Test tubes should be immersed in bowl of water). You will notice that gas is collected, since water in the test tube is displaced. Cover the test tube with a bung and put in the racking. As long as there is still a reaction, you can continue to collect the gas. Here is the chemical equation to show that reaction:

Calcium Carbonate + HCL --> calcium chloride + water + carbon dioxide

Testing:

To test that carbon dioxide is produced from the reaction, you can modify the procedure from above and instead of using test tube, use a boiling tube half filled with LIMEWATER or calcium hydroxide (slaked lime). Why Limewater? Because carbon dioxide turns a clear limewater cloudy. As the reaction takes place in the conical flask, cover it with the bung and insert the delivery tubing into the boiling tube with limewater. Wait and see, it should turn the limewater hazy or milky after few seconds.

References:

Wikipedia

WHY THE SKY IS BLUE?

2011-01-29T14:00:00.000-08:00

The sky is blue especially during bright days due to Rayleigh scattering. This scattering is the elastic scattering of electromagnetic radiation including light, by particles much smaller than the wavelength of the light. It can happen notably when light travels through gases or air. Rayleigh scattering of sunlight results in diffuse sky radiation, which is primarily the reason why the sky is blue and the sun look yellow.

As light travels through the atmosphere, most of the longer wavelengths just pass through straight away whilst some of the red, orange and yellow light, is affected by the air. Much of the shorter wavelength light, like the blue wavelength, is absorbed by the gas molecules, which is then radiated in different directions. It scattered all around the sky and so the blue colour seemed to occupy much of the sky.

EXPANSION OF GAS

2011-01-20T14:07:00.000-08:00

You could do a simple demo to show that gas expands as you heat it. If a substance is heated, the molecules in that substance start to move and soon take up more space – IT EXPANDS.

Activity

Prepare a gas flask with a rubber bung and glass tube.
Dip the end of the tube in a beaker of water.
Warm the flask by rubbing it with your hands or you may use other source of heat to speed up the process.

Observation

What do you see?

What do you think is expanding?

Do gases expand more than liquids?

What happens when you take your hands off and wait for the flask to cool

down?

Assessment

Explain how the concept of expansion affects the building designs and

bridges.

OH MY SALT!

2011-01-15T13:58:00.000-08:00

How can you get salt from a rock salt or seawater? This is a simple classroom demo to show that the common salt in the kitchen is mined from underground or can be taken out from the seawater.

You may use either rock salt or seawater (which ever is readily available in your school).

“ALWAYS BE CAREFUL WHEN DOING AN EXPERIMENT”

Materials/Apparatus

Rock salt ( or seawater)
Mortar and pestle
2 x 250 ml beaker
evaporating basin
tripod
bunsen burner
gauze
heatproof mat
goggles ( or any eye protection)
stirring rod
filter paper
funnel

Procedure

Crush some rock salt using mortar and pestle. (If using seawater, proceed to procedure c right away)
Put crushed rock into a 250 ml beaker and add enough water, and stir the mixture well.
Using the funnel, filter paper, and another 250ml beaker, filter the mixture or seawater. The water that comes out through the filter paper should be clear.
Put some of the filtered liquid into the evaporating basin and heat it. Turn off the Bunsen burner when crystals start to form around the edges of the solution and let the water evaporate without heating. Be careful because the salt will start spitting out of the basin.
The white crystals or powder left in the evaporating basin is called a pure salt.

Assessment

Describe the process of obtaining pure salt from rock salt or seawater.
Why didn’t filtering remove the salt from the water?
Plan an activity that could collect the water rather than the salt.

WANTED:CLEAN WATER

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An activity that can be done as a class experiment. Just make sure materials and equipment are available for the students. If not readily accessible in your school, ask groups to bring in materials.

This activity can be used when discussing about the importance of water. As a springboard of the topic, prepare pictures or powerpoint slides on water pollution, water scarcity in different parts of the world, sources of water, and etc. When it rains, water penetrates into the ground and as it passes through it, the water is filtered by the rocks, and sand, and soil, and eventually comes out as clean water at a spring or wells.

“ALWAYS BE CAREFUL WHEN DOING AN EXPERIMENT”

Materials/Apparatus

* 500ml plastic drink bottle ( with the bottom removed)

* small stones

* sand ( soil can be used, but not as good as sand)

* moss

* ruler/ wooden stick

* 100 ml muddy/dirty water to filter (you can prepare this by mixing soil and clean

water)

* 250 ml beaker (or drink glass)

* stand and clamp

Procedure

1. Push some moss into the bottle and use the ruler/wooden stick to push it down

2. Clamp the bottle upside down into the stand

3. Put a layer of sand on top of the moss

4. Put some small stones next to the sand enough to create another layer.

5. a to c makes up your water filter

6. Carefully pour the dirty water through your filter and observe. If the first lot of water looks a bit muddy, try it again,

Assessment

You may ask the students to make a diagram of the experiment and ask them to label each part correctly. Let them explain the importance of each part.

Note: If you have any questions or suggestions regarding this activity, you can reach me at my email in the Contact page.