Ency123

When light passes from one substance to another, it may also change direction. When light rays pass from air to water or from water to air, they bend as they pass through the surface of the water. This bending is called refraction. Refraction of Light Experiment: Can you bend a pencil? Can you bend a pencil without breaking it? You can make a pencil look as if it has been bent, by putting it in water. You will need: a glass water a pencil 1. Fill the glass halfway with water Put a pencil in the glass and lean it against the side. 2. Look at the water from the side The pencil will look bent. 3. Now take the pencil out of the water. Nothing has happened to it after all! Light rays pass through other substances, as well as air and water. They travel at different speeds as they pass through these substances. As rays pass out of one substance and into another, they are refracted. The amount that light is refracted depends on two things. The first is the co...

Do you have a flashlight?  Have you ever looked inside it?  A flashlight won't light up unless there are batteries inside. When you switch it on, the batteries make an electric current flow. This current flows through the bulb and makes it light up. When you switch on a flashlight, the batteries inside create an electric current by making electrons move. The electric current flows out of one end of the battery, through the bulb, and then back into the battery. As long as the current can move freely around this pathway, the bulb will light up. We call this kind of pathway an electric circuit. While the flashlight is switched on, the current continues to flow around and around the circuit. Turning the switch off makes a break in the circuit. Now the current can't flow, and the light goes out. Electric Circuit experiment You will need: two pieces of plastic-coated wire, about 8 inches (20 cm) long, with bare ends a screwdriver  masking tape  a 1.5-...

If we look very closely at some grains of salt, we will see that each grain has the same shape. Salt grains are shaped like tiny cubes. Regular shapes like this are called crystals. Many elements and compounds form crystals. The crystals in salt are easy to see. But other crystals are so small that you need to look through a microscope to see them. Sugar and ice form crystals. The atoms in different crystals join together to form different patterns.  There are seven basic patterns of crystal. The atoms of garnet form isometric crystals. The atoms of quartz form rhombohedral crystals. The atoms of zircon form tetragonal crystals. The atoms of beryl form hexagonal crystals. The atoms of topaz form orthorhombic crystals. The atoms of gypsum form monoclinic crystals. The atoms of feldspar form triclinic crystals. Many rocks and metals in the earth's surface are found as crystals, too. The crystals of each element or compound are the same. Crystals ar...

Like many metals, aluminum is a very useful element. It is found in rock as bauxite, which is an aluminum ore containing oxygen. The oxygen has to be removed before the aluminum can be used. The oxygen and the aluminum are joined so firmly that ordinary smelting does not remove the oxygen as it does with other metals. The best way to separate the aluminum and the oxygen is to pass electricity through them. This is called electrolysis. First of all, rock and sandy particles are removed from the aluminum ore. This leaves a white powder called aluminum oxide. It is made up of aluminum atoms joined to oxygen atoms. The powder is dissolved in a tank of chemicals and heated to about 1742 °F (950 °C). This makes the aluminum oxide melt and become a liquid. Molten aluminum collects at the bottom of the tank. Any impurities in the aluminum collect at the top, where the aluminum oxide cools to form a crust. Rods made of carbon are lowered into the molten aluminum oxide. An elect...

The colors of the rainbow are red, orange, yellow, green, blue, and violet. But these are not the only colors in the rainbow. If you look carefully at a rainbow, you can see that there are colors in between the red and the orange bands that are mixtures of the two. This is true for all the other main colors as well. The whole range of these colors is called the spectrum. The three most important colors of the spectrum are red, green, and blue. These are the primary colors of light. All the other colors you can see are mixtures of these three. If there are equal amounts of red, green, and blue light, you see this mixture as white light. Colors and wavelength Try to think of light as something that travels like waves. White light can be split up into different colors because each color is made up of waves of a particular length. The distance between the top of one wave and the top of the next wave is called the wavelength, and each color has its own wavelength. The colo...

The average human body contains about 1.5 kg of calcium. Major part of the calcium is in the bones as a major part of bone mass. Bone structure, we could compare with reinforced concrete. Bone has fibers called collagen fibers, similar to the flexible and iron wires that are placed in reinforced concrete. Calcium makes mass which surrounds the collagen fibers. The amount of calcium in our bones changes with age.  During the first year of life the child bones have very little calcium and are very flexible. The child can bend in all sorts of directions without breaking any bones. But when one experiences the age of 80, his bones can contain nearly 80 percent of calcium, and are easily breakable. To young children we give a lot of milk, among other things, because the milk is very rich in calcium, and young organism is, of course, in need a lot of calcium. One liter of cow's milk contains more than 1.5 g of calcium. Cheese, cream and yogurt also contain large amounts of calcium. ...