TATJANA MIHAJILOV–KRSTEV
Read interesting stories from the world of chemistry. Learn about the impact of chemical changes.
Perform experiments and examine chemical phenomena.
E MEET TH D WORL L A c i g a M istry Chem f o
50 CHEMISTRY EXPERIMENTS
Search for places where you can explore chemistry.
50
Get to know the scientists who studied chemistry.
Discover the magic of chemistry!
Illustrations
Nemanja Ristić Dušan Pavlić
Tatjana Mihajilov–Krstev
CHEMISTRY
50 Discover c of i g a M e th ry! Chemist
Tatjana Mihajilov–Krstev
CHEMISTRY Illustrations
Nemanja Ristić Dušan Pavlić
S
orcery and sorcerers... Whoever believes that today?! Those are tales for children, really small ones. Once you have found out something about nature and learnt that it is governed by nature’s laws, you stop believing those stories. But something unusual happened once. A swarm of bubbles flew out of a window on the building next door. They were floating across the yard, and the children were laughing trying to catch them. And when they touched them, the bubbles wouldn’t burst - they remained whole. And so, the truth was out – a real wizard lived in that building! Let’s go and meet him! He’s a chemist. He studies the structure of everything there is, the invisible forces that work in nature and the changes that happen. With him, we can discover the laws of chemistry and test them the way real scientists do. If you’re asking yourself what you are supposed to do, search for your answers in this book. It contains various experiments and interesting stories from the world of chemistry. You’ll see how interesting and exciting it is to perform chemical experiments!
Instructions
for the Experiments
Before
You Start...
1. Plan precisely everything you’ll do during the experiment. 2. Gather everything you need for the experiment. 3. Think through whether or not you need help in performing the experiment.
4. Find a suitable place for conducting the experiment. 5. Make sure you have ample time for work. 6. Let no one distract you while you are working!
Protective equipment is necessary for chemistry experiments. Thin rubber gloves and protection goggles can be bought in pharmacies or tool stores. You can make work clothes out of some big old shirt.
6
Once
You Get Started...
1. Be patient if an experiment requires more time than you expected. 2. Pay attention to the sign which warns you that an experiment must be performed , in a real chemistry laboratory
in the presence of an adult WITH AN ADULT
, LABORATORY
.
or in the open WITH AN ADULT
ORSAN ADULT LABORATORY OUTDO OUTDOORS WITH
OUTDOORS
LABORATORY
3. Follow the instructions to the letter. 4. Be careful not to spill anything during work. If you spill a chemical onto yourself, immediately wash yourself thoroughly with soap and water and inform an adult about it.
5. Don’t forget to enter your remarks into a notebook during the experiments. 6. Take photographs of the experiments’ phases which you think might be of use later. 7. Put the used dishes in a bucket with soap and warm water, and clean your work space after the experiments.
Planning an experiment is very important. However, even with a good plan, mistakes can happen. That is normal. Every explorer makes mistakes sometimes. If that happens, think carefully, and then repeat the experiment. Everything will probably go well then.
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AN ORDINARY ROOM
W
hen the chemist invited us to visit his lab, we started wondering if he was going to let us mix chemicals and if we’d be allowed to make fireworks. However, the room we entered was quite ordinary. air
Everything around us is matter. And the matter which occupies a space is a substance. That is what chemistry studies – different substances and their changes.
wall living beings water
soil
gravity which pulled the chair to the floor
chair
1. A Substance Model All substances are made of tiny particles between which there are empty spaces. Make a model of a substance.
What you need: • marbles, a glass, semolina flour
INSTRUCTIONS
1. Fill the glass with marbles. 2. Check if there are empty spaces around the marbles by pouring the flour into the glass.
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The semolina will fill the empty spaces around the What do marbles. you notice?
2. Is There Empty Space in a Full Glass? Water is a substance made of particles like marbles - they are just too small to be seen. Check if there are empty spaces surrounding the particles.
What you need:
• two glasses of the same size, two substances – semolina and water
INSTRUCTIONS
1. Fill one glass with water and the other glass with semolina so that it’s half-full. 2. Slowly pour the semolina from the glass into the water-filled glass.
What will happen? Why?
The semolina will fit in the glass without spilling over. When you fill a glass with water, it fills the entire space in the glass. The fact that semolina can also fit in the glass proves that there are indeed empty spaces between the particles of water.
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PARTICLES
P
articles which make up substances are called atoms and they are so tiny that they can’t be seen with the naked eye. They always cluster together with other atoms. The atoms constituted in this way are called molecules.
Molecules of some substances are built of one kind of atoms. Those molecules are elements. There are plenty of them and each has properties which make it different from other elements. Other substances have molecules which are made of atoms of different elements. Those substances are compounds.
Hydrogen and oxygen atoms
Молекул водоника
Молекул кисеоника
A molecule of citric acid In order for a compound to materialize, it’s not enough to merely mix the elements, but a chemical reaction must take place. Qualities of a compound differ from qualities of the elements which built it.
A molecule of sugar Greek philosopher Democritus (460 – 370 B.C.)
was the first who maintained that the whole world was made of tiny particles which cannot be broken down any further. He named such a particle an ’atom’ after the Greek word which means ‘indivisible’.
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3. A 3-D Model All molecules of a compound are built in the same way. A molecule of water always consists of one atom of oxygen and two atoms of hydrogen arranged in such a way that they resemble the head of a teddy bear °O°. Make a 3-D model of a water molecule and think about the fact that a raindrop has five hundred million molecules.
What you need:
• white and red modelling clay, toothpicks
INSTRUCTIONS
1. Make small balls of one kind of
modelling clay. These balls will be hydrogen atoms. Make slightly bigger balls. These balls will be oxygen atoms.
2. Cut the toothpicks into halves. 3. A molecule of water consists of an
oxygen atom and two hydrogen atoms. Put the atoms together into molecules by attaching one ball to both sides of the toothpicks.
Italian physicist Amedeo Avogadro (1776 – 1856) established that atoms cluster together into molecules. He also discovered that equal volumes of gases at the same temperature and pressure contain the same number of molecules. Based on this discovery (today known as Avogadro’s law), he managed to contrive a method for determination of atomic and molecular weight of all elements. 11
THE PERIODIC TABLE OF ELEMENTS
T
he elements can be presented in a table called the Periodic Table of Elements.
Gold is a precious metal. It’s used for making jewelry.
LANTHANOIDS (Lanthanum and other elements similar to it) ACTINOIDS (Actinium and other elements similar to it)
Mercury is a liquid metal. A drop of mercury in a thermometer indicates temperature.
* **
Dmitri Ivanovich Mendeleev (1834 – 1907), a Russian chem-
ist, spent a lot of time gathering data about chemical elements and thinking about how to arrange them in some sort of order. He made a table in which similar elements were grouped in the same columns - periods. For this reason, the table got the name the Periodic System of Elements. As many elements were still undiscovered at the time, Mendeleev left the gaps in his table for all of them to be filled on their discovery. Today, the table Mendeleev created is full, and the element with the atomic number 101 bears the name mendelevium in honor of the great scientist.
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Aluminum, a metal, made into foil is used for wrapping sandwiches. Helium is a gas lighter than air. A balloon filled with helium can fly high in the sky. The elements in the periodic table are grouped according to their likeness. Each group is colored differently, so that we are able to see at first glance what kind of element it is. NON-METALS METALLOIDS METALS NOBLE GASES Each element has its symbol, which features the capital initial letter of its Latin name.
`
There are plenty of elements. Some of them are all around us, and some aren’t easy to find. Scientists think that hydrogen is the most frequent element in space. Living beings, too, are made of elements. You are also made of carbon, hydrogen, oxygen, nitrogen, phosphorus, calcium, sulfur...
For example, C stands for carbon, because the Latin name for this element is carboneum.
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THREE GLASSES OF LEMONADE
T
he chemist started to make lemonade. He was doing it in such an unusual way that we couldn’t take our eyes off him. It turned out to be very useful, because without that special lemonade-making, we wouldn’t be able to make a single experiment in a chemistry lab.
I’ll show you how to make lemonade.
What you need:
• • a small bottle of water, a tall glass, three lemons, one pink grapefruit, a measuring cup with markers, sugar, a kitchen scale, a lemon-squeezer, straws, a funnel, a paper coffee filter.
INSTRUCTIONS
1. Pour 5 g of sugar into each glass (see the
5. Pour 20 ml of filtered juice into each glass
2. Add slowly 150 ml of water to each glass
6. Squeeze the juice from the grapefruit. 7. Add 5 ml of grapefruit juice to each glass
experiment No. 4).
(see the experiment No. 5).
3. Squeeze the juice from the lemons. 4. Filter the juice in order to remove the
flesh and the seeds (see the experiment No. 6)
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(see the experiment No. 7).
(see experiments 8 and 9).
8. Put the straws and teaspoons in the glasses so that everyone can stir the lemonade. Serve.
4. Measuring with a Scale Like any other hard substance, sugar can be measured with a scale. Lab scales are the most precise ones, but many kitchen scales are good enough for experiments conducted at home. Measure the sugar for each glass separately.
INSTRUCTIONS
1. Cut a square sized 10 x 10 cm out of foil. 2. Place the square on the scale and then set the
indicator to zero. You can do that by adjusting the small wheel or the button (if the scale is electronic).
3. Pour a flat teaspoon of sugar onto the foil and read the mass in grams. If necessary, add or remove sugar until you get the quantity of 5 grams.
5. Pouring Liquids Slowly In chemical experiments, sometimes it is necessary to add a layer of a liquid on top of another so that they don’t mix. A glass stick can be used for that, but a spoon will also do the job.
INSTRUCTIONS
1. Lean a teaspoon against the wall of the glass. 2. Pour water slowly and carefully down the spoon’s handle.
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6. Filtering Filter paper and a funnel are used for filtering. Chemists use glass funnels, but any funnel will do.
Notice:
You can also use a ready-made coffee filter for filtering, but only if it is a small one. A large filter is too big, and won’t fit into a funnel, but you can cut out a small piece of it and proceed following the instructions given here.
INSTRUCTIONS
1. Cut a circle around 10 cm in diameter out of the coffee filter.
2. Fold the circle in four
parts, and insert the paper cone into the funnel.
3. Place the funnel above the
glass and pour juice into it.
Filtering will go slightly
faster if you wait for the lees of the juice to settle at the bottom of the container from which you are pouring. After it has settled, first pour the liquid slowly and spill the liquid at the end.
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7. Measuring Liquids A graduated mixing cylinder is a tall, narrow vessel with markers used for measuring volume of liquids. Instead of it, you can use a measuring cup of a medicine or a small kitchen measuring cup. Measure the juice for each glass separately.
Notice:
Due to the attraction existing between the molecules of a liquid and the wall of a measuring cup, the level of the liquid is slightly lifted at the wall. That is why it is important to take notice of the lowest point of the liquid in the process of measuring.
INSTRUCTIONS
1. Place the measuring cup on a flat surface. 2. Pour the juice into the measuring cup until it reaches the 30 ml mark. 3. Take a look at the level of the liquid and observe: the surface isn’t flat, but slightly sagged in the middle.
4. Add the liquid carefully until the lowest line of the surface is on the same level as the 30ml mark.
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8. Measuring Very Small Amounts of Liquids
A pipette is a device used for measuring small amounts of liquids. It has marks on it so that the person making the measurement knows how much liquid he or she has taken. You can follow the same procedure using a straw – the only difference is that it has no marks. This is where the information that 1 ml of liquid fits into the shorter part of a straw - the one that goes to the flexible part - can be useful. This means that you will have to take grapefruit juice five times in order to get 5 ml.
Notice:
5ml or 10 ml volumes can be measured with a spoon which you get with medicines, as well as the measuring cup on a bottle cap of a children’s medicine.
INSTRUCTIONS
1. Take a pipette with the thumb and the middle finger and insert its tip so that it reaches the bottom of the glass with juice.
2. Close the opening of the pipette with the index finger and lift it from the glass. Watch the
level of the juice. When you lift the index finger for a moment, a small amount of the juice will leak out of the pipette, but as soon as you put the finger back on the opening, the juice will stop leaking.
3. Make sure that the amount of juice in the pipette is the exact amount you need.
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9. Adding Liquids Drop by Drop A device used for accurate measuring of liquids is a dropper, or a pipette with a small balloon attached to it. For adding juice you can also use a drinking straw on top of which you will put a small bottle made of soft plastic. You can also use a medicine dropper, but first, you must wash it thoroughly.
Notice:
A straw is used for drinking juice, but a liquid must never be drawn by mouth. Various small plastic or rubber balloons are used for sucking a chemical into a pipette.
INSTRUCTIONS
1. Squeeze the balloon (or a small bottle) so as to force the air out of it. 2. Insert the tip of the dropper into a glass with water and slowly release pressure on the balloon. 3. When the dropper is filled with water, remove it from the glass. 4. Press the balloon really slowly and the drops of liquid will come out of the dropper one by one.
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LABORATORY
C
oming to a chemistry laboratory for the first time is an unforgettable experience. Everything in it is adjusted to conducting experiments. There are neatly arranged vessels of most unusual shapes in the cupboard. There are plenty of bottles on the shelves. Some bottles are small, and some are big. Some are dark, because the substances in them are sensitive to light. The danger sign is on some of them. Grrr! Can a person touch anything here?
Here are safety goggles and gloves for everyone! And we can use old shirts instead of lab coats.
EVERY BOTTLE MUST HAVE A LABEL USE CLEAN TOOLS FOR EXPERIMENTS CHEMICALS MUST NOT BE INHALED
LABORATORY PROTECTIVE EQUIPMENT IS NECESSARY
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Appropriate tools are required for performing chemical experiments. They can be bought from stores with lab equipment. An experiment can also be performed with a glass juice bottle instead of an Erlenmeyer flask, and a plastic syringe with milliliter marks instead of a graduated cylinder.
pipettes
test-tube rack
test tube
glass funnel
Erlenmeyer flask
test tube holder Bunsen burner
graduated cylinder
beakers
metal lab spoon
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CONTENTS 6 INSTRUCTIONS 8 8 9
AN ORDINARY ROOM A Substance Model Is There Empty Space in a Full Glass?
10 PARTICLES 11 A 3-D Model 12
THE PERIODIC TABLE OF ELEMENTS
14 15 15 16 17 18 19
THREE GLASSES OF LEMONADE Measuring with a Scale Pouring Liquids Slowly Filtering Measuring Liquids Measuring Very Small Amounts of Liquids Adding Liquids Drop by Drop
20 LABORATORY
86
22 24 26 27 28 30
NEW CONDITIONS Winter Monsters Smoke Screen Magic Potion A Cloud of Your Own A Cannon Shot
32 33
A BREAK: TIME TO THINK The Disappearing Caramel
34 36 37 38 40 41 42 44 45 46 47
MIXING Who’s Faster? Separation of Colors Invisible Partitions The Indecisive Liquid The Disappearance of the Color The Light in the Fog A Sea in a Bottle An Underwater Eruption Durable Bubbles Magic Powder
48 49 50 52 53
A FRIENDLY CHAT Sweet or Too Sweet A Rainbow in a Straw A Chemical Shelf Tiny Submarines
54 WHERE’S THE LEMONADE? 55 Acidic Color 56 Cabbage-Detective 58 59 60 62 63
YOU CAN’T BEAT SUGAR A Treat A Watery Garden The Blossoming Stick The Magic Touch
64 65 66 67 68 69
A CHEMISTRY GALLERY Timid Colors Room Decorations Painting with Nail Polish A Snowy Rainbow Slimy Figurines
70 71 72 74 75 76 77 78 79 80 82
CHANGES From a Mixture to a Compound A Chemical Fountain A Garden Volcano A Gigantic Paste Moon Ground The Black Mamba A Smoke Catcher The Chameleon Blasting Lanterns in the Night
84
ABOUT THE AUTHOR
84
INDOOR FIREWORKS
86 CONTENTS
87
TATJANA MIHAJILOV–KRSTEV
Read interesting stories from the world of chemistry. Learn about the impact of chemical changes.
Perform experiments and examine chemical phenomena.
E MEET TH D WORL L A c i g a M istry Chem f o
50 CHEMISTRY EXPERIMENTS
Search for places where you can explore chemistry.
50
Get to know the scientists who studied chemistry.
Discover the magic of chemistry!
Illustrations
Nemanja Ristić Dušan Pavlić
Tatjana Mihajilov–Krstev
CHEMISTRY