What happens when something burns?
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Let's start by making some observations.
What do you see in this video? What is going into the flame? What is coming out of the flame? |
Atoms vs. Molecules
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Atoms are the building blocks of matter. Unlike wood toy blocks that we can see and touch, these building blocks are incredibly small. In fact, they are the smallest particles of an element. Atoms still have the same properties as the elements they make up. For example, an atom of gold has the same melting point as a gold coin. If we could see it, it would have the same color. Elements are also pure substances. This means they are not mixed with anything else. All the atoms of a given element are the same. This means that all the atoms of gold in a gold coin will be the same but the atoms of a silver coin will be different than those of the gold coin.
Atoms can be alone or bonded to other atoms. When there is more than one atom bonded together we call it a molecule. A molecule can be made of all the same type of atom or of different types of atoms. Water molecules are made of 2 hydrogen atoms and 1 oxygen atom. That's why we call it H20. Some atoms, like oxygen and hydrogen, like to be bonded to other atoms. You will never find just one atom of oxygen in nature. It will always be in the form of a molecule, either bonded to another oxygen atom or bonded to a different type of atom, such as a carbon or hydrogen atom. Other atoms like to be alone. Helium will never be found bounded to another atom. Helium doesn't form molecules, it aways stays as atoms in nature. |
Atom Rules:
Atoms last forever (except in nuclear changes).
Atoms make up the mass of all materials.
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This text is adapted under a Creative Commons 4.0 license. You can find the original source here.
Energy
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Energy comes in two forms; potential energy and kinetic energy. Potential energy is stored energy. Kinetic energy is the energy of motion. A stretched rubber band has potential energy because it has the potential to fly through the air, but until you release it, it isn't moving. Once you release the rubber band the potential energy is transformed into kinetic energy (energy of movement). Chemical energy is a major form of stored, potential energy. Chemical energy is the energy stored in the bonds of molecules. When you break the bonds of the molecule you release some of the energy that was stored in the bonds.
There are a lot of different types of energy. You are probably familiar with light energy, heat energy, sound energy etc. Energy can be transformed from one type of energy to another. But you cannot create energy or destroy energy. For example, when you bounce a ball on the ground you transfer energy from your hand to the ball, as the ball moves it has kinetic energy. When the ball hits the ground some of the energy from the moving is transformed into heat energy and some of the energy is transformed into sound energy. Once the ball stops bouncing all of the kinetic energy will have been transformed into heat and sound energy. |
Energy Rules:
Energy lasts forever.
Chemical energy is stored in the bonds between atoms Changing bonds (making/breaking bonds) either requires energy or releases energy. |
More about Chemical Energy
What is chemical energy? Every atom has a small nucleus, made of protons and neutrons, and electrons that circulate outside the nucleus. Electrons are like other particles because they move naturally toward low-energy places or states close to the nucleus, like balls that roll downhill.
Molecules and chemical energy exist because many atoms have either too many or too few electrons. Carbon and hydrogen have extra electrons; they could be more stable if they could get rid of or share some of their extra electrons. Oxygen, on the other hand, does not have enough electrons; oxygen atoms would be more stable if they could add some electrons.
Chemical bonds and molecules. Molecules exist because electrons can move to other atoms. When carbon and hydrogen share electrons, the shared extra electrons can move to lower-energy states. Oxygen atoms can also become more stable by gaining electrons to “fill their gaps.” Atoms that share electrons stay close together, so those shared electrons are the chemical bonds that keep atoms together in molecules.
High-energy and low-energy bonds. Carbon and hydrogen atoms can lose a little energy (like a ball rolling a little way downhill) if they share electrons with other carbon and hydrogen atoms. But they still have their basic problem--extra electrons— so we say that C-C and C-H bonds are relatively weak high-energy bonds. BUT if carbon and hydrogen atoms can give their extra electrons to oxygen atoms (remember oxygen atoms have too few electrons), then they can lose a lot more energy (like a ball rolling farther downhill). So we say that C-O and H-O bonds are stronger low energy bonds.
Keeping track of chemical energy. There are several methods of keeping track of how much energy is transformed during a chemical reaction. Chemists can make accurate calculations of the amount of energy by using Hess’s Law. In this unit we won’t try to be that accurate, though. Instead, we will be sure to notice whenever carbon atoms have high-energy bonds that could be replaced by low-energy bonds.
We will use twist ties to identify high-energy C-C and C-H bonds. Those bonds have extra electrons that could lower their energy by getting close to oxygen atoms. If that actually happens--if the electrons move from C-C or C-H bonds to C-O or H-O bonds— then we can use the twist ties to remind us that energy was released in the process, and changed into some other form of energy such as heat, light, or motion.
What is chemical energy? Every atom has a small nucleus, made of protons and neutrons, and electrons that circulate outside the nucleus. Electrons are like other particles because they move naturally toward low-energy places or states close to the nucleus, like balls that roll downhill.
Molecules and chemical energy exist because many atoms have either too many or too few electrons. Carbon and hydrogen have extra electrons; they could be more stable if they could get rid of or share some of their extra electrons. Oxygen, on the other hand, does not have enough electrons; oxygen atoms would be more stable if they could add some electrons.
Chemical bonds and molecules. Molecules exist because electrons can move to other atoms. When carbon and hydrogen share electrons, the shared extra electrons can move to lower-energy states. Oxygen atoms can also become more stable by gaining electrons to “fill their gaps.” Atoms that share electrons stay close together, so those shared electrons are the chemical bonds that keep atoms together in molecules.
High-energy and low-energy bonds. Carbon and hydrogen atoms can lose a little energy (like a ball rolling a little way downhill) if they share electrons with other carbon and hydrogen atoms. But they still have their basic problem--extra electrons— so we say that C-C and C-H bonds are relatively weak high-energy bonds. BUT if carbon and hydrogen atoms can give their extra electrons to oxygen atoms (remember oxygen atoms have too few electrons), then they can lose a lot more energy (like a ball rolling farther downhill). So we say that C-O and H-O bonds are stronger low energy bonds.
Keeping track of chemical energy. There are several methods of keeping track of how much energy is transformed during a chemical reaction. Chemists can make accurate calculations of the amount of energy by using Hess’s Law. In this unit we won’t try to be that accurate, though. Instead, we will be sure to notice whenever carbon atoms have high-energy bonds that could be replaced by low-energy bonds.
We will use twist ties to identify high-energy C-C and C-H bonds. Those bonds have extra electrons that could lower their energy by getting close to oxygen atoms. If that actually happens--if the electrons move from C-C or C-H bonds to C-O or H-O bonds— then we can use the twist ties to remind us that energy was released in the process, and changed into some other form of energy such as heat, light, or motion.
Organic vs. Inorganic
At one time in history, it was thought that only living things were capable of synthesizing the carbon-containing compounds present in cells. For that reason, the term organic was applied to those compounds. Eventually it was proved that carbon-containing compounds could be synthesized from inorganic substances, but the term organic has remained. Currently, organic compounds are defined as covalently bonded compounds containing carbon, excluding carbonates and oxides. By this definition, compounds such as carbon dioxide (CO2) and sodium carbonate (Na2CO3) are considered to be inorganic. Organic chemistry is the study of all organic compounds.
Organic chemistry is a very vast and complex subject. There are millions of known organic compounds, which is far more than the number of inorganic compounds. The reason lies within the uniqueness of carbon’s structure and bonding capabilities. Carbon has four valence electrons and therefore makes four separate covalent bonds in compounds. Carbon has the ability to bond to itself repeatedly, making long chains of carbon atoms as well as ringed structures. Carbon readily makes bonds with other elements, primarily hydrogen, oxygen, nitrogen, halogens, and several other nonmetals.
What this really means is that organic molecules have C-C and/or C-H bonds. Because these molecules have high energy bonds they are molecules that are able to burn. There are some basic rules you can use to figure out if a molecule is organic or not.
Organic chemistry is a very vast and complex subject. There are millions of known organic compounds, which is far more than the number of inorganic compounds. The reason lies within the uniqueness of carbon’s structure and bonding capabilities. Carbon has four valence electrons and therefore makes four separate covalent bonds in compounds. Carbon has the ability to bond to itself repeatedly, making long chains of carbon atoms as well as ringed structures. Carbon readily makes bonds with other elements, primarily hydrogen, oxygen, nitrogen, halogens, and several other nonmetals.
What this really means is that organic molecules have C-C and/or C-H bonds. Because these molecules have high energy bonds they are molecules that are able to burn. There are some basic rules you can use to figure out if a molecule is organic or not.
- Does it burn? If the molecule can burn then it is organic and you know it has high energy bonds.
- Does it have C-C or C-H bonds? If the molecule has these high energy bonds then it can burn and it is organic.
- Does it come from a living thing? If it is part of the body of a living thing then it is organic.
- Is it a food? Foods come from living things which means they are organic.
- Is it a fuel? Fuels like coal, oil, and gasoline can burn. They also come from living things. These are both indicators that fuels are organic.
- Is it a plastic? Plastics are made from fuels and they can burn. Plastics are organic.
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