Chemical Reactions

This experiment is designed to follow the basic lab notebook setup for an advanced lab notebook based on our Sample Lab Notebook Setup document. The section titles in red correlate to the sections in your lab notebook. Please refer to this document when setting up a lab notebook for the first time and for younger children.

Experiment Title:

Does mixing Vinegar with Baking Soda create a chemical reaction?

Objective:

The objective of this experiment is to learn about basic chemical reactions. This will be done by students mixing various amounts of baking soda and vinegar together to see if they can drive a chemical reaction (first object) and then see if they can figure out what type of reaction is occurring when the two reactants are mixed together (second objective).

Background on Chemical Reactions:

A chemical reaction is when one or more substances are added together or have something done to them to induce (create) a change in the initial substance or substances. There are many different types of chemical reactions: irreversible, reversible, precipitation, acid-base (aka. neutralization), Oxidation-Reduction, Combustion, Synthesis, Decomposition. We go through a look at each type of reaction at a high level (only learning very basic information but not necessarily going in depth with every detail, if you want to learn more about chemical reactions go to https://chem.libretexts.org/Core/Inorganic_Chemistry/Chemical_Reactions/Chemical_Reactions, [1]).

Irreversible Reaction – A reaction in which you cannot get the original reactants (ingredients) back out of the reaction in their original state (you mix an egg with flour you can never get the egg back the way it was when it was added to the flour) - When you bake something you take a bunch of ingredients (eggs, flour, salt, chocolate, butter, sugar, etc…) and mix them together, then you add heat and the ingredients become something completely new (a chocolate chip cookie for example). Now with our baking example the reaction is irreversible (a reversible reaction you can get the original ingredients back out) this means that we could not take our chocolate chip cookie and reverse the baking process to get the eggs back out[1]. 

Reversible Reaction – A reaction in which you can do something to the original reactants to change them in some way (could be a phase change (going from liquid to solid or vapor to liquid for example) or dissolving something as the most common examples) then reverse that process (reversing a process it typically doing the opposite of what you did initially) - Now think about cooling water, in cooling the water (if you cool it enough) the water will go from a liquid to a solid state (so from water you drink to ice that you use to cool a drink such as cranberry juice). Now if water becomes ice does it stay ice no matter what? The simple answer is no (yes it could stay ice forever say if you put it in space and it never came in contact with a heat source or frictional source), meaning that at some point heat will be added to the ice and potentially turn it back into liquid water (it could also be turned directly from solid to vapor in a process called sublimation, but we will get into states of matter another week). In this case you have taken water in a liquid state and removed heat (cooled it) to form solid water (forming ice) then added heat to the solid water and turned it back into liquid water, this type of chemical reaction is a reversible reaction (you put in something and you get the exact same thing out when the process is reversed)[1]. 

Precipitation Reaction – this is where to or more reactants that have been dissolved in a liquid (this makes them aqueous reactants which is important when you get into higher level chemistry) when mixed together form a compound (a combination of the reactants) that is insoluble (cannot be dissolved in the liquid) this means that the compound will precipitate (fall out of the liquid) and form a layer of compound at the bottom of the liquid – most of the reactions you have probably seen so far will not be precipitation reactions, but some of your favorite candies could be from them. Think about rock candy (the blocky sugar candy that is typically on a wooden stick), rock candy is made by supersaturating (putting even more than that liquid could normally dissolve usually by adding heat (although cold liquids can dissolve more gases than warm liquids, super awesome isn’t it!)) water with sugar. You heat the water close to boiling and add sugar until no more sugar can be dissolved (this means that even with stirring you can still see a few sugar crystals at the bottom of the pan you are mixing it in). Now if you pour this liquid into a glass and add a stick then let it sit for a couple weeks (usually two) crystals of sugar will start to grow on the stick and make your rock candy (to add flavors and colors mix them in once you have the solution in the glass and only ever do this experiment with your parents as heating the liquid can be very dangerous and cause severe burns)[1].

Acid-Base (Neutralization) Reaction – this is where you take an acid (a substance that can dissociate to have more + ions than – ions, confusing but hang in there I will explain in just a minute) and a base (a substance that can dissociate to have more – ions than + ions). Let’s make this a bit simpler, say you are at school and have a positive attitude (which is exactly what you want to have at school, school is awesome!) and you run into a bully who has a negative attitude (maybe they are just having a rough day), now the two of you join together to play a game (because you are awesome and know how nice it is to be nice to others and help them have an awesome day). If your positive attitude is at the same level as the bully’s negative attitude when you begin and with the game your attitudes cancel out (not likely as you are very positive, but for this example let’s say so) then you both would have a neutral attitude meaning that neither of you would be positive or negative this creates a neutralization reaction. Now when your attitudes do not balance each other out you will have either a negative attitude overall or a positive attitude overall which is simply an acid-base reaction (not a neutralization reaction because you still have a bit of + or a bit of – left over). Now you being a reactant is awesome and you should be proud of the great job you did, the same idea holds for chemicals reacting, some have a positive charge and some have a negative charge, when they cancel each other out you get a neutralization reaction, which is an acid-base reaction that is simply balanced[1].

Oxidation-Reduction Reaction – these reactions have to do with the movement or sharing of electrons (the negative portions of an atom) between one atom or molecule or another – now most of you have not been exposed to this level of chemistry just yet, but do not worry there are simple ways to think about it. When you have a molecule that can share an electron with another molecule or atom. The molecule that gives up the electron is oxidized and gains a positive charge (remember in the acid-base reactions the H+ or the positive attitude this is essentially what you are making a positive molecule). The molecule that accepts (takes) the electron is reduced and gains a negative charge (this is like a neutral kid getting a negative attitude because they fell off the swings, but they can always go back to neutral by sharing that electron or story in the future). A common example of an oxidation-reduction reaction is when an adult cuts an apple for you, at first it is sweet (if not a little tart) and a nice light tan color, but say you go out to play and come back an hour later and it is brown and maybe a little bitter on the surface but the inside is just like when it was first cut. The inside of the apple when exposed to air oxidizes and turns brown[1].

Combustion Reaction – these reactions are what happens when you burn a fuel (carbon based materials such as wood, gas, oil, etc… are fairly common examples of fuel that can be combusted) in the presence of Oxygen (you need oxygen to burn things (think about a candle, you light the wick (with your parent’s permission and supervision) and once it is burning you place a lid on the candle, what happens to the fire? It goes out after all the oxygen that is in the candle container is burned up)) and get water, carbon dioxide (sometimes a few other molecular compounds as well but for simplicity lets stick with water and carbon dioxide). Now we know that combustion involves fire, but did you know that most cars (those are run on gas or diesel) use combustion reactions to make energy! The gas/diesel (these materials are very dangerous and should never be played with or experimented with, if you want to learn more about how they work look at this basic physics tutorial http://ffden-2.phys.uaf.edu/211_fall2002.web.dir/David_Giessel/basics.html) is burned in the presence of oxygen to create heat and drive the mechanical components of a car so that it can move[1]. 

Synthesis Reaction – is when you combine two or more reactants to form one compound (a combination of the reactants) – let’s go back to our chocolate chip cookie example, we put in flour, sugar, salt, butter and chocolate chips and after applying heat (baking it in the oven) we get one final compound a chocolate chip cookie, we took ingredients and synthesized a chocolate chip cookie compound[1].

Decomposition Reaction – this reaction is the reverse reaction of a synthesis reaction, you take a compound and split it into different atoms or molecules that when combined make up that compound – our cookie can never be (nothing is impossible but with our current technology let’s stick with never in this example) broken back down into the components that we added together to make the cookie, Hydrogen Peroxide (this is stuff that your mom might keep in the house for cleaning stuff or using on her hair, it is very dangerous if ingested (swallowed) and should not be used without adult supervision) when this is broken down it makes oxygen and hydrogen. Not a super easy example to follow I know but if we do something silly and treat salt water as if it is a single compound meaning that you have one material in it as opposed to a salt (NaCl for example broken down (would become Na+ and Cl-) in water (H2O) that may also be broken down (H+ and OH-) then we can pretend it can be decomposed (so we are assuming we have some fictional compound H2ONaCl) using heat (this would evaporate the water (H2O) and leave NaCl (this is the basic idea of a solar still even though we really do not have a decomposition reaction the idea is the same start with one thing and get two or more things out of it, solar stills are really neat and if you want to learn more about them check out this article https://en.wikipedia.org/wiki/Solar_still)[1].

These were just a few examples of different types of reactions that we can see when doing experiments. Chemists, Biologists, Chefs, Bakers and Engineers to name a few work with these types of reactions every day. Now it is your turn to make some reactions of your own.

Materials

-        4 medium Clear Plastic Cups

-        4 small Clear Plastic Cups

-        Vinegar

-        Baking Soda

-        Lab notebook

-        pencil

Method

Prepare Experiment

1. Baking soda is a very neat reactant, a simple white powder that is grainy when felt with very little smell (remember how to waft a smell, gently wave the reactant under your nose from left to right, you do not breath in the reactant but passively smell it as it moves). Vinegar is also very cool it can be used for pickling things like cucumbers (makes pickles with some salt and water added in), waft this as well, doesn’t smell so good or does it?
2. Now get your cups and spoons setup for your experiment, don’t forget to write down your experiment in your lab notebook.

Run Experiment

1. Now we are going to see what happens when you mix together vinegar and baking soda. Using the big cups measure (use your spoons, each spoon is equal to a teaspoon or 5 mL) the basic amount or different amounts of vinegar that you want to use for each experiment, remember to write out each amount in a table in your lab notebook.
2. Using the small cups measure the basic amount or different amounts of baking soda that you want to use for each experiment, remember to write out each amount in a table in your lab notebook.
3. Make sure that you keep track of which cup of baking soda is being added to which cup of vinegar. In which ever order you decide add one amount of baking soda to one amount of vinegar (do not add the vinegar to the small cup containing the baking soda or you may make a mess). Record your results
4. Repeat this for the last three reactions.

Analyze Data

The cool thing about observations and experiments is that everyone has their own unique way about going about making and doing them. Let’s all share our observations of what happened to our baking soda and vinegar, there are no wrong answers with your observations. Did adding more baking soda or more vinegar change what you observed?

Conclusions

In this experiment we added baking soda and vinegar together in order to create a chemical reaction. For most of you some sort of reaction should have occurred, this should have led to bubbling of the reactants and the formation of a gas. After the reaction you should have attempted to determine the type of reaction that was occurring, here is the overall reaction that occurred:

CH₃COOH + NaHCO₃ → CH₃COONa + CO₂ + H₂O

Look at the reaction in another way

CH₃CO+ -OH + Na+ -HCO₃ → CH₃COO- +Na + CO₂ + H₂O

You have a basic acid-base reaction when the different materials dissociate and react together. CO₂ is slightly acidic so in the end after everything has reacted provided some of the CO₂ is dissolved in the water you will have a minorly acidic solution. If all of the CO₂ escapes as gas the solution should be roughly neutral meaning that the reaction is a neutralization reaction. How cool is that?

Make It Your Own

Think about your vinegar and baking soda reaction (this is the same basic reaction used in many school volcanos) with your parents’ permission you could make a simple volcano and add food coloring to your vinegar in order to make red lava. This experiment was designed for all of our young scientists to be able to do with adult supervision, now think about what you did and make it your own at home with your parents. Think about the experiment, if you were to add something other than baking soda to the vinegar (say salt or flour) does that change your reaction? What if you add sugar in addition to the baking soda? Is your reaction slower or faster or unchanged?

Extension Activities to do at home

Chemical reactions are everywhere, if you can find some common chemical reactions that you see everyday? See if you can figure out what type of reaction a battery is undergoing (this will not be evident looking at the battery, but with your parents permission you can look at this website on basic battery chemical reactions http://hyperphysics.phy-astr.gsu.edu/hbase/electric/battery.html. This is a lot more advanced than we did in STEM Club but remember this pneumonic device AN OX RED CAT (at the anode you oxidize, and at the cathode you reduce, that is a big hint as we only talked about oxidization and reduction in two of our reaction types that we discussed). Now consider doing a precipitation reaction (look back at the section on precipitation reactions) and try making rock candy (make sure your parents do this with you, it is not safe to work with boiling sugar water on your own or use the stove without permission).

Citations

[1] Chemical Reactions, Retrieved December 26, 2017, from https://chem.libretexts.org/Core/Inorganic_Chemistry/Chemical_Reactions/Chemical_Reactions