The grade 6 English science unit, Combustion, meets the academic content standards set in the Korean curriculum, which state students should:

Transcription

1 This unit deals with the concept of combustion, the reaction responsible for a wide range of phenomena, such as the burning of candles. It also addresses fire extinguishment, the opposite of combustion and a concept that must be studied in order to live safely. By studying this area, students should discover the conditions required for a substance to undergo combustion or extinguishment by observing the phenomenon of burning and learn that new substances are created as a result of combustion through experiments. They also develop the ability and mindset needed to manage emergency situations in everyday life.

2 The grade 6 English science unit, Combustion, meets the academic content standards set in the Korean curriculum, which state students should: a) Learn through observation the common phenomena that occur as a result of the combustion of substances. b) Know the conditions of combustion and fire extinguishment as well as understand combustion and fire extinguishment in relation to each other. c) Examine the substances produced as a result of combustion through experiments. d) Be aware of fire prevention and safety measures and know how to properly handle a fire extinguisher.

3 What do I need to do? You will need vinegar, empty pet bottle, baking soda, a tablespoon, filter paper, a candle, a lighter, a straw, and a stopper with a hole in the middle. 1. Mix 50mL of vinegar and half a tablespoon of baking soda together in the bottle. 2. Put a straw in a stopper that has a hole in the middle and place this on the bottle. 3. Light a candle. Carefully tilt the bottle near the flame. Make sure the liquid doesn t exit the bottle. A fire needs three things for it to start and continue burning. It needs fuel (something to burn), oxygen and heat. These three things are known as the fire triangle. To stop a fire, all you need to do is take one of the fire triangle things away. You could take away the fuel, oxygen, or heat. Fire extinguishers are often used to put out fires. There are different types of fire extinguishers, but the material inside is able to take the oxygen and/or heat away. It is important to know how to use a fire extinguisher. They are very efficient in putting out fires in its early stages. The P.A.S.S acronym is an easy way to remember how to use them; Pull. Aim. Squeeze. Sweep. 1. What three things does a fire need to start and continue burning? 2. How does a fire extinguisher help to put out fires? 1

4 What do I need to do? You will need a crayon, a clip, a metal bowl, a lighter, ethanol, and a tall glass jar. 1. For solid fuels: Put a crayon in a clip. 2. Stand the crayon up in a metal bowl. Light the crayon by aiming the flame of the lighter to the side of the top of the crayon. 3. For liquid fuels: Your teacher will pour some ethanol in a tall glass jar and swirl it around. They will light the vapor in the jar using a lighter. One of the things needed for a fire to start is fuel. The most common examples are natural gas, propane, kerosene, diesel, petrol, charcoal, coal, and wood. Most fuels, such as wood, gas and petrol, are made up of hydrogen and carbon. When they burn, they release water and carbon dioxide. Combustion of a liquid fuel happens in the gas phase. It is the vapor that burns, not the liquid. Therefore, a liquid will normally catch fire only above a certain temperature. This is the temperature where enough of the liquid fuel has evaporated in the air to catch on fire. 1. What are three examples of fuel commonly used? 2. For liquid fuels, is it the liquid that burns? Please explain. 2

5 What do I need to do? You will need play dough, matches, fireproof desk, and a lighter. 1. Make a long worm with the play dough and put it on a fireproof desk. 2. Put matches in the play dough so that they are very close to each other. Near the end remove some of the matches so that there is a big gap. 3. Light one end of the matches and observe what happens. A huge earthquake hit Tokyo in It started many fires which quickly spread through the city at a very quick pace. This was because the buildings in Tokyo were mostly made of wood, which is a perfect fuel for fires. Also, the buildings were very close together, which allowed the fires to move easily from building to building. About 66% of the city was burnt down in fires that lasted for two days. When Tokyo began to rebuild itself, it began to make more spaces between the buildings to act as a firebreak. A firebreak is simply an open space that can stop fires from spreading. Also, some buildings began to use fireproof materials. 1. Why was it so easy for Tokyo to burn down after the earthquake in 1923? 2. How could they have prevented the fires from spreading at such great speeds? 3

6 What do I need to do? You will need 3 matches, a metal bowl, and a heater. 1. Break three matches in half. 2. Put the matchheads on one side of the metal bowl and the wooden ends on the other side. 3. Turn on the heater and observe what happens. Heat is one thing needed to start combustion. Different materials will start to burn at different temperatures. The lowest temperature required for a substance to start burning is known as the kindling point. A substance that burns in air is called flammable. Research has shown that once a material reaches a certain temperature in the presence of oxygen, it will start to burn. A common household item, called linseed oil has started some very bad fires. Linseed oil is often used to protect wood. However, if it is left on rags, it will start to evaporate very quickly. As this happens, the rag can get very hot. The heat is enough to start a fire. The fire in this apartment began due to linseed oil being left on a rag. 1. What does kindling point mean? 2. What are the dangers of leaving linseed oil on a rag? 4

7 What do I need to do? You will need copper wire, a pencil, a candle, and a lighter. Your teacher will need a metal bowl, paper, a lighter, a plastic container, and water. 1. Wrap some copper wire around the end of a pencil. Leave some wire unwound so that you can hold it like a handle. 2. Light a candle. Hold the copper wire in the flame and observe what happens. WARNING: Do not let the wire get too hot, or it will burn you. 3. Watch your teacher demonstrate another method of taking away the heat from a fire. Heat is transferred from hotter objects to colder objects. It is possible to transfer the heat produced by the fire to another object. If the heat transfer is enough, you can take away the heat from the fire and it will go out. Metal is a great conductor of heat and can take away the heat of very small fires. Water is also a great material for taking away the heat from a fire. Pouring water on a fire usually puts out the fire. Water can be used if the fuel is wood, paper, or plastics. However, if the fire is due to grease or other flammable liquids, water cannot put out these fires. If anything, it can make it worse, as the flammable liquid can float on top of the water and will spread as the water flows. 1. How does water put out a fire? Firefighters using water to put out a fire. 2. Can water be used to put out all fires? Please explain. 5

8 What do I need to do? You will need steel wool, a lighter, scissors, and a metal tray. Your teacher will need hydrogen peroxide, yeast, an empty pet bottle, measuring spoons, and a candle. 1. Watch your teacher demonstrate how oxygen affects a flame. 2. Cut open the ball of steel wool. Unroll it and place it on a metal tray. 3. Set fire to the middle of the steel wool with the lighter. Oxygen is one of the things needed to start a fire and to allow it to keep burning. Adding pure oxygen to a fire allows it to burn very brightly and quickly. It can be dangerous. If you try to set fire to your metal knife or fork with a lighter, you won t be able to do it. This is because iron is a good conductor of heat and can transfer the heat around so that the utensil can t get hot enough. Steel wool, however, is made up of tiny little strands that make contact with a lot of oxygen in the air. Once fire comes into contact with the steel wool, it burns very well, as it can make enough heat and is surrounded by enough oxygen to keep it going until all the fuel is used. A lot of oxygen can lead to a fire becoming very dangerous. 1. What happens to fires that are exposed to lots of oxygen? 2. Why can steel wool burn so well, but not solid iron objects? 6

9 What do I need to do? You will need a small jar, a large jar, 2 candles, 2 petri dishes, water, and a lighter. 1. Put a candle in each of the petri dishes. 2. Fill the petri dishes with some water. 3. Set fire to the two candles. Put the two jars over the candles at the same time. Observe what happens. Fires need oxygen. If you put a fire in a closed jar where air can t get in or out, the fire will eventually go out. This is because the fire will use up all the oxygen in the jar to keep itself burning. With no more oxygen, the fire goes out. Also, the fires produce carbon dioxide gas. As the fire in the jar uses up the oxygen, it is also making carbon dioxide gas. In the opening experiment of this unit, we made a fire extinguisher that put out a fire. It was the carbon dioxide gas that put out this fire. Containers that hold a larger volume of air will let a fire burn longer, as there is more oxygen available for the fire to use. This fire extinguisher uses carbon dioxide to put out fires. 1. Why did the fires go out in the jars? 2. Why did the fire in the smaller jar go out first? 7

10 What do I need to do? You will need baking soda, sugar, scales, spoons, a metal bowl, sand, lighter fluid, and a lighter. Your teacher will need ethanol, a lighter, and a tall glass jar. 1. Watch your teacher demonstrate complete combustion. 2. Mix 10g of baking soda with 40g of sugar. 3. Pour some lighter fluid on the sand in a metal bowl. Then, put the baking soda/sugar mixture on top in a mountain shape. Use a lighter to set it on fire. Fuels burn when they react with oxygen and there is enough heat. Many fuels are hydrocarbons, which mean they are made up of hydrogen and carbon. The oxygen from the air will join with the hydrogen to form water and the oxygen will join with the carbon to make carbon dioxide gas. If this happens, it is known as complete combustion. The flames are blue in color. However, if there is not enough air we get incomplete combustion. The hydrogen will still combine with the oxygen to make water, but the gas made here is carbon monoxide. In this case, carbon is also released as soot or smoke. The flame also takes on an orange color. 1. What things are made in complete combustion? 2. How is incomplete combustion different to complete combustion? 8

11 What do I need to do? You will need colored candles, and a lighter. Your teacher will need sparklers, boric acid, copper sulfate, a spoon, and a lighter. 1. Watch your teacher light some fireworks. Observe the colors. 2. Watch your teacher burn different elements. Observe the colors of the flames. 3. Use a lighter to light candles that have been made with different elements. Observe the colors of the flames. Every year people enjoy watching fireworks as they brighten the night skies. People also enjoy using birthday candles that produce a variety of colors. The colors are a result of different elements that burn in different colors. Lithium or strontium adds a red color to the flames. Sodium helps produce the gold and yellow colors. Magnesium helps to make bright white flames. Barium is used to create green flames. Copper creates the blue colors. Aluminum creates silver sparks and flames. Titanium also helps to make sparks. Antimony helps to make the glitter effects. 1. What causes fires to come in different colors? 2. How do humans use this knowledge of flame colors in everyday life? 9

12 What do I need to do? Your teacher will need rubbing alcohol, a crucible, tape, a rotating stand, a metal meshed umbrella stand, and a lighter. 1. Your teacher will pour some rubbing alcohol into the crucible. 2. They will tape the crucible onto the middle of the rotating stand. 3. They will light the rubbing alcohol and spin the rotating stand. Observe what happens. People usually think of large, whirling winds when they hear the word tornado, but it can be more than just the air. In very bad forest fires, firefighters sometimes have to battle against fire tornadoes. This effect happens as the winds blow through the trees and collide with the warm, rising air from a wildfire. As the warm air rises, cooler air moves into the bottom of the fire, providing more oxygen for the fire and also helping to twist the flames into the shape of a tornado. These fire tornadoes can be up to 50 meters tall. This phenomenon shows how a fire can spread quickly through a forest. The fuel is usually gases given off from plants that are heated. The gas can travel up the middle of the tornado until it can mix with enough oxygen to set it on fire. 1. What causes a fire tornado? 2. What is a potential fuel for fire tornadoes? 10