Molecules or Compounds
Chemistry is a really cool field of science, but it involves learning a lot of vocabulary. This can be daunting when you're first starting to explore chemical reactions. For example, you've probably heard of molecules and compounds, but how exactly are they different?
A molecule is when two or more elements are chemically bonded together. A compound is two or more different elements chemically bonded together. Wait, what?
Try re-reading the last paragraph, and see if you can pick up on the difference between the two terms. Got it? Here's the major difference: a compound has two or more DIFFERENT types of elements bonded together. As you know, there are 118 elements on the periodic table. To have a compound, there needs to be at least two of these elements. Let's look at some examples.
Believe it or not, compounds are all around us. Simply turn on your faucet and water will come pouring out. Water's chemical formula is H2 O, which means there are two hydrogen atoms bonded to one oxygen atom. So, is water a compound? Let's run down the checklist: Are there two different types of elements in water? Yes! Hydrogen and oxygen. Therefore, water is a compound.
Ready for another one? Alright, look at your kitchen table and find the salt shaker. Table salt's chemical name is sodium chloride and is represented in formula form as NaCl. There is one atom of sodium (Na) chemically bonded to one atom of chloride (Cl). Again, we have two different elements joined together, and thus table salt is considered a compound.
You are doing great. Take a big breath in, and exhale it. Okay, so you just blew a compound out of your mouth! The air that comes out of your mouth when you exhale contains carbon dioxide, and carbon dioxide's chemical formula is CO2 because there is one carbon atom bonded to two oxygen atoms. Because carbon dioxide is made up of two different types of elements, carbon and oxygen, it is considered a compound.
Okay, last example, and it's tricky! When you breathed in, your lungs were filled with oxygen. Oxygen's chemical formula is O2 because one atom of oxygen is bonded to another atom of oxygen. Is this a compound? No, oxygen is not a compound. There are two elements chemically bonded together, but they are the same type of element. Therefore, the oxygen we inhale would be considered a molecule.
The reason the terms molecules and compounds are especially confusing is because one includes the other. For you see, all compounds are molecules, but not all molecules are compounds.
This sounds complicated, but let's replace these words with something more familiar and see if it doesn't become clear. All apples are fruit, but not all fruits are apples. This makes sense right? If I showed you a grape and asked 'Is this a fruit?' you'd say 'Yeah,' even though it's not an apple.
It's the same for compounds and molecules. A compound is a specific type of molecule. Is sodium chloride (NaCl) a molecule? Yes. Is it a compound? Yes. Is oxygen (O2) a molecule? Yes. Is it a compound? No.
In summary, a molecule is when two or more elements are chemically bonded together, meaning they are two of the same kind. But a compound is when two or more DIFFERENT types of elements are chemically bonded together. So start exploring your environment and see how many compounds you can discover!
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Card Game Activity for Practicing with Elements, Compounds, and Molecules:
- A molecule is formed when two or more elements are chemically bonded together.
- A compound is formed when two or more different elements are chemically bonded together.
- 118 note cards with the 118 elements from the periodic table on them
- A piece of paper and a pencil
Steps to the Game:
- Mess up the note cards face down in a pile.
- Draw 3 cards, and record them or just place them face up in front of you.
- Write down three compounds or molecules that you can think of that can be made from the cards chosen, and explain why it is a compound or a molecule.
- Repeat as many times as desired.
Examples and Practice Questions:
- Suppose the cards drawn are sodium (Na), chloride (Cl), and hydrogen (H), and the list you come up with is salt (NaCl), molecular hydrogen (H2), and sodium hydride (NaH). Which of these are compounds, and which are molecules? Explain.
- Suppose the cards drawn are hydrogen (H), oxygen (O), and iron (Fe), and the list you come up with is water (H2O), two oxygen atoms (O2), and iron oxide or rust (Fe2O3). Which of these are compounds, and which are molecules? Explain.
- Salt (NaCl) contains two different elements, sodium and chloride, so it is a compound. Molecular hydrogen (H2) contains two atoms of the same element of hydrogen. Since H2 contains two or more elements, but the elements are not different, molecular hydrogen is a molecule. Sodium hydride (NaH) is made up of two different elements, sodium and hydrogen, so NaH is a compound.
- Water is made up of two different elements, 2 hydrogens and 1 oxygen, so H2O is a compound. Two oxygen atoms (O2) are two elements, but they are the same element, so O2 is a molecule. Iron oxide (Fe2O3), or rust, is made up of two different elements, 2 irons and 3 oxygens, so Fe2O3 is a compound.
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