Alternative Energy Sources

In the future, we can assume our electrical needs will be just as great as they are now, and likely greater. However, this means we will have to be careful. Many of the sources of energy we use are non-renewable, meaning that we can't get more after we've used up what we have. One non-renewable energy source is fossil fuels. These are resources such as coal, oil, and natural gas. We are using these up quickly, and once they are done, there will be no more for thousands of years. Not only are they being used up quickly, their use contributes to global warming. We need to find alternative sources of power.

One possible source of power is nuclear energy. We can convert a tiny amount of nuclear mass into a lot of energy, and it does not pollute. However, nuclear power plants are expensive, the waste left over remains radioactive for thousands of years, and accidents can have huge impacts on the environment.

Another possibility is tidal power plants. These use the power from waves and water to generate electricity. The use of this sort of power is limited to coastal areas, but the earth's surface is mostly water, so we don't need to worry about running out any time soon. However, these types of power plants affect marine life and harm coastlines. Hydroelectric power, where the power of rivers is harnessed to produce electricity, is not limited to coastal areas and produces no pollution, but it requires an expensive dam to be built and interferes with fish migration.

Wind power is an option. Wind turbines are used in open areas and produce a lot of power. However, the wind doesn't blow every day. The power of the sun is also a possibility. Solar cells convert the sun's rays into electrical energy, but they are expensive and require direct sunlight.

While we figure out which power sources are best, we need to be more careful of our energy consumption. We won't have fossil fuels forever, and we need to take care of our environment.

Most circuits contain many loads. What happens when there is more than one resistor in a series, and they are parallel?

When resistors are arranged in a series circuit, the current passes through each resistor, down the line. In a parallel circuit, some power goes down either side of the circuit. A waterslide analogy can be used to explain the difference between an electrical circuit with two resistors in series and an electrical circuit with two resistors in parallel.

Each circuit consists of two slides. The electricity going through the circuit are the people going on the slides. One waterslide has the two slides connected, creating one long slide. The other has them separate, parallel to each other. People can choose to go down either slide. A person who slides down the longer slide will take longer going down, and fewer people will be able to go down the slide. On the parallel slides, more people will be able to go down.

Resistance

A resistor is part of a circuit that resists the flow of electrical current. It is the load in a circuit and converts the electrical energy to another form of energy. The unit of measurement for resistance is the ohm portrayed by the green letter for omega.

The amount of resistance offered by the resistor is determined by what it is made of, the size of the resistor, and the temperature. The resistance increases with length and decreases with diameter.

Ohm's law was determined in 1827 by Georg Simon Ohm. He discovered that the ratio of voltage to current was constant to a given conductor. The relationship can be written as an equation (above). R is resistance (in ohms). V is voltage. I is the current. All conductors resist electricity to a certain extent. Not all of them, however, obey Ohm's law. The resistance of a material depends on its temperature, and resistance increases with temperature. The law forms the basis for the definition of resistance, but it is not technically a law because it does not apply in all circumstances.

Electrical energy is carried through a circuit by electrons. The energy each electron has is called electric potential energy. It is measured in volts. Because electric potential energy is measured in volts, it is often called voltage. A voltmeter is a device that measures voltage. It can be connected onto the energy source or the load. When you connect the device to the positive and negative terminals of a battery, it measures the difference in volts between both sides.

It used to be thought that when an electric current flowed through a circuit, it was the positive charges which were moving. Now, we realize this is incorrect, and that the negative charges flow through a circuit. They flow from the negative terminal to the positive terminal of the energy force. The electric current from an electric cell flows in one direction. This is called direct current (DC). DC is used in battery-operated devices, such as watches. Alternating current (AC) is used in wall outlets. Alternating current occurs when the electrons periodically reverse direction. In a North American AC unit, the current reverses direction 60 times per second.

An ammeter measures the amount of electric current at a point in a circuit. It is connected in series with the circuit. A multimeter also measures current, among other things.

 We use current electricity all the time. Every time you turn on a light, turn on the oven, or even turn on a flashlight, you are using current electricity. Current electricity is electrical charges flowing in a circuit in a controlled way. An electrical circuit is a continuous path for energy to flow through.

A flashlight is a very simple electrical circuit. If you've taken it apart, you know there's not much to it. A switch to control a wire, two batteries, and a light bulb, contained inside a tube. The batteries are the energy source and the bulb is the load, the switch controls the flow of electricity, and wires to connect it all together. The joule (J) is the unit for measuring energy. A light bulb in a table lamp needs about 4000 J per minute it is on.

There are different sources of electrical energy. An electrical cell, for example, converts chemical energy into electrical. There are two types of electrical cells. Primary cells cannot be recharged. Secondary cells can. Two or more electrical cells is a battery. The load in an electrical device is what converts the energy into a different form. The light bulb in a flashlight, for example, converts the electrical energy into heat and light energy.

There are three ways an object can be charged. One is friction. If two objects are rubbed together, then some of the electrons will have a stronger attraction to one of the two objects, and some of the electrons will transfer over.Objects can also be charged through conduction. Charging by conduction occurs when objects touch and an electric charge is transferred. If you walk across a carpet and get a shock from touching a metal doorknob, this is from conduction.

Objects can also charge without any contact. When dust builds up on a computer screen, and the screen is turned on, the dust gathers a charge. When a neutral dust particle comes near the screen, the screen induces an opposite charge on the near side of the dust particle, attracting it to the screen.

Electricity is basically electrons moving quickly from atom to atom. An insulator is a substance in which the electrical charge cannot move to another object. Substances such as plastic, rubber, and glass are insulators. A conductor is on object through which an electrical charge passes easily. Most metals are good conductors. A semiconductor allows the electricity to travel through them, but not as easily.

We use electricity for a lot of things. If we didn't have it, life as we know it wouldn't exist. However, we cannot see electricity directly, but we can observe its effects. For example, if you walk across a carpet, then touch something metal, you might feel a slight spark. This is called static electricity. It is "static" because it is at rest. It stays on you until you touch the metal. Eventually, if something is charged for long enough and the energy stays on it, the something is "discharged", loosing the charge.

There are two types of electric charges, negative and positive. Positive charges repel each other. As do negative. Negative and positive charges attract, however. The particles that make up all matter, atoms, contain these charges. Atoms are composed, however, of even smaller particles. There are protons, positively charged, electrons, negatively charged, and neutrons, which do not have any charge. Protons and neutrons are in the center of the nucleus of an atom. Electrons move around these in various orbits. If the atom contains the same amount of electrons and protons, they cancel each other out and the atom is neutral. If not, it has an electric charge. An atom with a charge is called an ion. A negative ion has a negative charge, and a positive ion has a positive charge.

Electrons can be transferred between two objects. If two objects rub together, one looses electrons and the other gains. Now they both have a charge. Some objects are more likely to lose or gain electrons.

Making the Red Planet Green

Our planet is the only one known to be able to support life. But what if we had to leave, make a new home on another planet? Our two closest neighbors are Venus and Mars. They are about the right distance from the sun to house life. Venus, unfortunately, has poisonous gases in its atmosphere, making it  a poor choice for a home. However, Mars does not. Would we be able to turn it into a home, if we had to?

To make the red planet green, we would need an atmosphere that could support life. There are large amounts of carbon dioxide in Mars's polar ice caps. If we could raise the temperature of the planet, it would start to melt. Hey, we've managed to do it here - why not on Mars, too? If the temperature of Mars went up, water in the planet would start to melt. We would need this water, since the price of shipping would be huge if we wanted it from Earth.

Another problem is the amount of nitrogen in the atmosphere. Earth has 70%. Mars has 3%. Nitrogen is essential to life. We would have to bring nitrogen in. This could be done by taking rockets out to the asteroid belt and selecting certain ones with plenty of nitrogen, then driving them back. This, however, turns an already incredibly ambitious project into a near impossibility. In the best case scenario, if everything went well, after this was done, it would take a hundred years to complete. Growing plants on Mars, which would be necessary, is made difficult by radiation.

If everything went smoothly and we could grow plants, the oxygen levels might be enough to just barely survive on Mars in a thousand years. Then there would have to be volunteers who would move to Mars. But, if we ever actually could terraform Mars, we would probably find a way to clean up Earth, which would be easier anyhow.

We can't explore space in the same way we can our own world. If we want to explore a certain part of our own world, we go ourselves. But we can't travel in space, at least, not very far. So how do we explore the stars? One of the earliest tools for studying the stars was the astrolabe. It works in in much the same way as a protractor in geometry, measuring angles. It was used to calculate the difference between the stars and planets.

Nowadays, we have more advanced tools. These instruments measure the waves of radiation given off by objects in space. There is a spectrum to measure how much various objects give off. At the right end of the spectrum, we have gamma rays, X-rays, and other rays. At the other end are radio and infrared rays. We can see only a very tiny amount of these rays, the ultraviolet rays, which make up the rainbow.

Radio telescopes pick up radio waves. The telescopes pick up waves, then amplify them and send them to a computer, which processes the information. By studying these waves, scientists can learn about far away galaxies and planets that are far, far away.

Infrared telescopes pick up on the waves that we feel as heat. We can't see the signals, but can sense them instantly. These allow astronomers to guess at the temperature of a certain object. Some snake have eyes that locate prey by detecting sources of heat.

Ultraviolet telescopes need to be placed outside of Earth's atmosphere in order to work, since our atmosphere blocks out most ultraviolet rays. They pick up on the ultraviolet rays. New stars and many of the most active objects in the universe emit these rays.

We have many inventions with which to explore the solar system. And, in time, who knows? Maybe we will be able to look for ourselves.

Bug eyed aliens are the stuff of science fiction. They are shown in many books and movies attempting to take over our planet. But do we really have anything to worry about? Aside from us, is there intelligent life in the universe?

The short answer is we don't know. But since this post should probably be a bit longer, I'll ask another question. Is there a good chance of intelligent extraterrestrial life in the universe?

We have not yet made contact with extraterrestrials. SETI, the Search for Extra Terrestrial Intelligence, has not found anything. We have sent out satellites with greetings in various languages, in hopes that, if the satellite finds anything, they might be able to decode what we're saying. However, for life to exist on a planet, it has to have very certain conditions for life. We haven't seen any planets that could sustain life aside from our own. On top of that, where would the life have come from? Life can't create itself.

If life did exist out there, there's little chance we'll ever see it. If we traveled at one tenth the speed of light, a trip to our nearest star would take 43 years. And enormous amounts of energy is necessary for such travel. Moving at the speeds this type of travel require is dangerous. Hitting a single speck of dust could do serious damage to the outside of a space ship.

Some people like to think that the government knows about the existance of aliens and is covering it up. Why would they do that and continue to spend millions of dollars on the search for them?
So it's unlikely we'll find intelligent life any time soon. But still, who knows?

What's Outside the Solar System?

Most people know what makes up the solar system. The planets, which revolve around the sun. But what's outside the solar system?

Well, to answer that question, where does the solar system end? Well, past Pluto, one of our dwarf planets, we have a thin haze of dust. This dust is held in the sun's gravitational pull, so it is part of our solar system. This dust may stretch out halfway to the nearest star, approximately 4.2 light years away. There are many, many different types of stars in the Milky way. At our very center, there is thought to be a black hole, hidden by the clouds of the constellation Sagittarius.

The universe is mostly empty space. But since the universe is so big, there's still plenty to see. One of our neighbors is the Large Megellanic Cloud. It is made of of stars, gas, and dust. There are star clusters inside it, and nebula, which are dust and gas, from which stars are sometimes born. There are neighboring galaxies, such as the Andromeda Galaxy. Sometimes, galaxies are pulled into orbit around another. They collide and form new galaxies. It is thought that one day, our galaxy with collide with Andromeda.

An Elevator to Space

The idea of an elevator to space has been around since the 1960's. It comes from an idea for a satellite attached to Earth by a strong cable. Vehicles could travel to and from the satellite along the cable. Unfortunately, there are problems with this idea.

The cable could not be pulled behind a space vehicle as it took off, as it would slow it down. So it would have to be lowered from space. If a heavy cable is lowered from a satellite, the satellite's center of gravity changes. The satellite must go higher in order to adjust. A cable lowered in this fashion would have to be very long. A good design for this estimates the cable will be about 90,000 km long. This is long enough to circle the Earth. Twice.

The cable would also have to be strong. Steel wouldn't work. Not even diamond fibres. However, carbon nanotubes would work. A cable made of these would be light and thirty times stronger than steel. This cable would also be incredibly thin. The original design was for it to be 100 times thinner than a piece of paper. The entire cable could weigh 20,000 kg. The cable would likely be anchored offshore.

There are still problems. The cable could easily be damaged. And we actually don't know how to make a cable like the one required. The longest rope we've made out of nanotubes is only a few centimeters long. And the elevator can't exactly be tested. We can't only go part of the way up, then a little further. The cost of such a venture would be more than ten billion dollars. If we can work past these problems, however, we might soon be taking elevators to space.

Getting into Space

Rockets are how mankind has always traveled in space. However, they are also expensive. A rocket's energy equivalent is around 20% of that of the nuclear bomb that was dropped on Hiroshima. The rocket that sent the astronauts to the moon cost $500 million dollars to launch. NASA has determined that the space shuttle needs to be retired and is working on other ways to take man into space.

So how will we get into space in the future?

One possible way is by giving the shuttles a little boost. For example, flying them up to a certain height where they can fire off their rockets and take off into space. The problem with this idea is that, to do so, the shuttle would have to be light. And, with the fuel required to get into space, the shuttles are not light.

In Jules Verne's book, From the Earth to the Moon, the space vehicle is fired from a gun barrel three football fields long. Canadian scientist Gerald Bull tested this theory and shot a 16 inch projectile into space. It is possible that, in his later career as a weapons designer, he was working on creating a much larger version of this that could shoot objects into orbit. He was thought to be building this weapon for Saddam Hussein's Iraqi government, however, and was assassinated.

With the technologies being developed, who knows where we might go next?

Happy Easter, Everybody!!!!!!

Have you ever wondered why Easter's date changes?

It's called a "movable feast". A movable feast is a "holy day" which is not fixed according to the calendar but moves in response to the date of Easter. Such days include Good Friday, which is set two days before Easter.

Why does Easter move? The First Council of Nicaea, which was a council of bishops in 325 AD who were attempting to sort out issues with dates and such in Christianity, declared it to be so. The Christians had generally just asked their Jewish neighbors which days it was, since it was at the same time as Passover, one of their own festivals. However, some Christians felt that the Jewish calendar was unorganized and inaccurate.

The council decided to create their own, independent calculations to determine the date of Easter. The holiday was declared to be the first Sunday after the full moon following the Northern Hemisphere's vernal equinox, the beginning of Spring. Ecclesiastically, the vernal equinox is on March 21, although it actually occurs on March 20 most years. The date of Easter, therefore, varies between March 22 and April 25.

Happy Easter, everybody!!!!!!

Galileo discovered Saturn's rings in 1610, using his newly invented telescope. His telescope, however, wasn't clear enough for him to tell they were rings. He thought they were large moons, almost half the size of Saturn. However, when he observed Saturn later, the moons had disappeared. Later, an astronomer discovered that the "moons" were actually a flat disk, which had been turned edge on to Earth when Galileo observed it. Saturn's rings turn edge-on to Earth every fourteen years. After that, another astronomer discovered that the flat disk was actually rings around the planet.

The rings of Saturn start about 6,000 kilometers from the planet and extend 480,000 kilometers. They are wide, but very thin, about a kilometer thick on average. They seem to be made up mostly of small particles of ice and rock. There are seven rings altogether.

Other planets also have rings. A spacecraft, sent to Jupiter, flew right through them with no one noticing anything at the time. The rings are as wide as Saturn's, but darker. Neptune and Uranus also have thin rings.

Eventually, the rings of Saturn will dim. Micrometeorites will smash the ice crystals in the rings. Left will be fragments of black rock and metal and dirty ice. This process will wear away at the rings. The rings will gradually grow darker and thinner until there is nothing left. Enjoy them while you can.

In 2006, Pluto was officially declared not to be a planet anymore. It was, instead, announced a dwarf planet. What caused this decision?

Pluto is tiny - scientists think it's about 2,300 kilometers in diameter. There are several moons in our solar system larger than the planet. Another feature that caused it to be demoted is its orbit. The planet's orbit cuts through that of Neptune's.

Scientists began to find objects beyond Pluto. They were mostly smaller than Pluto, and have been named Kuiper Belt Objects (KBOS). There is estimated to be at least 70,000 that are over 100 kilometers across. In 2000, astronomers started to find objects closer to Pluto's size. Then they found Eris. Eris was larger than Pluto. It cuts inside Pluto's orbit when closest to the sun and, when furthest, is twice as far as Pluto's orbit. It takes more than 550 years to circle the sun.

All these discoveries meant that, if Pluto was to be called a planet, then Eris should be called one too, as well as many KBOS. Scientists, in 2006, voted on the definition of a planet. A planet had to be a sphere. A planet had to be in orbit around a star. And a planet couldn't be with a group of other objects, orbiting peacefully. That was the final blow for Pluto. It is now classified as a dwarf planet.

Space Junk

Space is full of junk.

When the astronauts went to the moon, they left trash there. Very expensive trash. The amount of trash in space is becoming a problem. And with more satellites going up every year, the amount is growing quickly. It is estimated that there is nearly 2 million kilograms of space junk in low Earth orbit. Much of this is being tracked as it orbits the earth. There are about 10,000 objects that are about the size of a grapefruit or larger.

If a piece that large were to hit a satellite or space station, it could do some serious damage. If an object a centimeter or larger, moving at 40,000 kilometers an hour, were to hit something, it would be the equivalent of throwing a bowling ball at speeds of 500 kilometers an hour at a human being. The Space Shuttle has returned with large chips in its windshield (I don't think there are winds in space, but you know what I mean) that came from colliding with a speck. Impacts from space junk have been thought to disable two satellites.

So what can we do? Most of this junk will eventually fall to Earth. However, this can take a while, and it's a hazard to astronauts. There is a 1 in 91 chance that an astronaut could be hit with a piece big enough to penetrate their suit. The astronaut would be very lucky to survive. As if their jobs weren't already full of dangers.

Black Holes

Black holes are regions of space that have such massive gravitational pull that not even light can escape. No one has ever directly seen a black hole. There is thought to be one in the center of our galaxy, 40,000 times larger than the sun.

How is a black hole formed? There are many theories. The most common is that when a big star, about three times the size of the sun, reaches the end of its life, its stability cracks under its own gravity. The radius of the star shrinks and it starts to devour everything that's close enough. We cannot actually see a black hole. However, we can see the area of space affected by it. It is the event horizon, where there is no light. It is called a horizon because, like a horizon on our own planet, we cannot see beyond it.

If you enter an event horizon of a black hole, you will start to accelerate under the influence of gravity. You may start to orbit around the black hole, bumping into other pieces of matter. The jostling might throw you away from the black hole, or it might knock you into it. It won't go black as you go over the event horizon. You'll be able to see what's outside of the event horizon. The light everywhere will appear strange and distorted by the gravity.

If you look down, you'll see the singularity, which is a point where all physical laws have, basically, become indistinguishable from each other. At this point, you will begin to stretch and very quickly loose interest in what is going on around you. Fortunately, this should be fairly quick. Predictions about the inside of a black hole can be made, but it eventually gets too weird for science to describe. And a visit to a black hole is highly inadvisable.

Even More Poisonous Plants...

Common Snowberry





Symphoricarpos albus and related spp.

Snowberries are sometimes grown as ornamental shrubs in North America and Europe. One child, after eating three berries, experienced mild sedation, vomiting, and slight dizziness. Others have died from eating them. In several indigenous languages, they are known as ghost berries or corpse berries.

Calla Lilies



Zantedeschia aethiopica and related spp.

When ingested, this attractive flower causes intense burning of the mouth and throat. however, it is seldom fatal. They are grown as houseplants in many places, although they are native to South America.

Jack in the Pulpit



Grows in much of Eastern North America. The plant causes salivation, nausea, and vomiting. Very rarely, it causes irregular heart beat, fits, coma, and death. Fortunately, the plant burns when it is swallowed, so a fatal dose is rare.

Buttercups



Ranunculus spp. and related genera

Attractive yellow flowers. They are found throughout North America. The fresh plants can cause painful blistering of the skin and irritate the mouth. However, they taste horrible, so it is rare that they are eaten in quantity. However, a fatal dose is not impossible.

More Poisonous Plants...

Black Hellebore

Helleborus niger and related spp.

An herbaceous perennial, with the flowers blooming in winter or spring. Poisoning is rare, but can be fatal. Symptoms of poisoning involve cramps, nausea, visual disturbances, and vomiting.

Larkspur and Delphinium



Consolida ajacis, Delphinium spp.

These plants grow in many gardens. Their poison is similar to that of aconite, a highly poisonous plant. The amount of poison in these plants depends on the age of the plant and the species, but a fatal dose is not impossible.

Hemlock



Conium maculatum

Carrot like plants. The root can be mistaken for carrots and the leaves for parsley. The plant has an unpleasant taste and smell, which is fortunate, since it is deadly poison. It was used to kill Socrates and is said to be a very humane way to die. Initially, those who eat it will feel stimulated, then fall into severe depression of the nervous system, became paralyzed, and die if not helped.

Energy plays an important role in chemical reactions. A chemical reaction that stores energy is called an endothermic reaction. In photosynthesis, solar energy is stored in the sugar molecules. Most endothermic reactions store energy in the form of heat. Another endothermic reaction is putting a chemical ice pack on an injury. The chemicals inside are stored separately, but when mixed feel cool against the skin.

Exothermic reactions are the opposite of endothermic. These release energy. Burning something is an exothermic reaction. So is the reaction that digests your food. As food molecules are broken down, energy is released that the body uses to function.

Catalysts

A catalyst is something added to a chemical reaction in order to speed it up. The reactants have to reach a certain energy level before they can react, and a catalyst can speed up the process. It reduces the amount of energy needed for the reaction. For example, chlorophyll is a catalyst that speeds up photosynthesis. Enzymes are also catalysts, found in living cells. They are used in reactions that are involved in digestion, cell construction and reproduction. If we did not have enzymes, we would be unable to produce glucose at the speed our body needs it, so these are essential to life.

What do you add if you want to slow a reaction down? You use a negative catalyst. If a chemical reaction, such as food spoiling, is occurring, it can be slowed down, by things like fruit freshener. Negative catalysts, or inhibitors, help keep the reactants apart, or bond with other reactants so the reaction will not take place.

Reacting

Chemical reactions occur when two or more elements combine and form a new substance or when a substance is broken down into its seperate elements. Chemical reactions are everywhere. Bread rising is a chemical reaction. Fireworks going off is a chemical reaction. Fire burning is (well, I suppose you've already guessed this) a chemical reaction.

Reactions often change heat. An exothermic reaction, for example, is one where the product is hotter than what went into it. If the product is cooler than its reactants, then its called an enothermic reaction. There are many different sorts of chemical reactions. If an element combines with oxygen, the reaction is an oxidation reaction. If oxygen is removed from a substance, it is called a reduction reaction. If elements other than oxygen combine, then the substance formed is called a composition reaction. If a substance is broken down, it's called a decomposition reaction. Some reactions, like rust, occur very slowly. Others happen quickly, like fireworks.

In order for a reaction to take place, the reactants must all be in contact with each other. The size also matters. A cube of iron will rust more slowly than a sheet with the same amount of material, because the thin sheet has more surface area and the oxygen in the air can react with more iron particles. The concentration of the reactants also speeds up the reaction. The more molecules of each reactant, the more likely they are to come in contact and react. Heat can also increase the speed of the reaction, because it causes the heat causes the molecules to move more quickly. Adding a catalyst can also help. A catalyst speeds up the reaction, but is not used up.

Metallic Bonding

Metals do not form ionic bonds with each other. An aluminum atom, for example, has three valence electrons. It cannot form a bond with another aluminum atom. If one aluminum atom gives up its three valence electrons to another atom, it would have six valence electrons and not be stable. If an aluminum atom gave up its three valence electrons to two other atoms, there would still not be enough electrons to make them stable. Metals also do not form covalent bonds. Metals usually only have one two or three valence electrons with which to make the atoms stable.

How, then, do metals form bonds? The best theory so far seems to be the free electron theory. According to this theory, thousands of atoms join together. The electrons of these atoms move around freely to form stable atoms. This theory is called metallic bonding. It also explains why metals conduct electricity so well. The free movement of the electrons is what helps conduct electricity and give metal its shiny appearance.

Bonding

There are two types of bonding in atoms - ionic and covalent.

Ionic bonds are when two elements join and exchange electrons. They usually form when a metal and a nonmetal bind together. Ionic bonds are responsible for salt, a mixture of chlorine and sodium, or copper fluoride. Ionic bonds tend to form crystals. They have high melting points. They are hard and brittle, dissolving in water, and conduct electricity when dissolved. Ionic bonds prefer to have eight valence electrons, to satisfy the octet rule. The octet rule states that atoms want to have eight valence electrons. When they do, they are at their most stable. Ionic bonds are like Lego sculptures. If you hit them, your hand will just bounce off because they're tightly packed. Your hand might also hurt, too, depending on how hard you hit it.

Covalent compounds are different. They are usually formed when two nonmetals bind together. Covalent bonds are different because they share electrons, not exchange them. Covalent compounds are things like carbohydrates, proteins and water. They are strong but flexible. If you hit a covalent compound, it would be less like hitting a Lego sculpture, and more like hitting a ball pit. They have low melting points, compared to ionic compounds, and don't easily dissolve in water.