Which Apple would you Buy?

1 teachers like this lesson
Print Lesson


SWBAT design an investigation using controlled and manipulated variables.

Big Idea

Understanding how to test a question and setting up the investigation takes time and patience. This lesson offers the chance to do all that.

Preparation and Materials Needed

5 minutes

This lesson connects beautifully to K-2 ETS-1. It offers the chance to create and set up a real world scenario. The question is a real question, that at one time, was really tackled in the apple industry. Because of this, it suddenly has a purpose that must be investigated to discover a possible solution. 

This lesson takes two days to complete. It is necessary to do all the preliminary work on the first day to set up the lesson and make all the predictions before observing the results. 

I gather up all the materials before the lesson begins.  Having the materials ready and prepared ahead of time, saves valuable teaching time. 

One apple (cut into small cubes: each team will need four cubes of apple)



lemon juice

baking soda 

small cups 

stirring sticks

small spoons

small eye droppers

plates to keep each team's materials together

labels for each team

student safety goggles (The goggles we use are actually from my dentist office. They are the goggles that you wear when you have your teeth cleaned. I asked my dentist one day if I could purchase some from their supplier.  My dentist graciously helped me with this). 

My choice in the solutions we are investigating is simple.  The lemon juice needs to be utilized because it is really the one solution that ensures freshness in the fruit.  Of course, in an actual factory that is producing this product, it is much more complicated than straight lemon juice, but for the purpose of the lesson, it works.  The other solutions are readily available to most households.  I want to use simple ingredients that the students could potentially replicate at home again with their families if they choose to.

Engage - Day 1

5 minutes

If you are familiar with those little apple slices that come in a package, you know who the "Crunch Pak" folks are.  They produce those packages in a small town just outside of where I live.  Many of the children have family that work there.  This offers me a great tie in and personal connection for some of my little people to really dig into this investigation.  

I begin with a question....."If I was the owner of Crunch Pak, how would I want my apple slices to look when I sold them in their packages? Would I sell many apples if they were brown and mushy?"  

After this question is posed, I have the kids do a heads together and discuss this question for about two minutes.  I ring my bell, and the children quiet down.  The team leaders for the day, immediately stand up and are ready to share out their team's response.  

I am sure that I will hear things like....."We believe that our apples, should look like they are fresh." Or something similar to this, describing a fresh cut apple.  At this point in the year, the teams have been working very hard to explain their thinking when it is time to share out.  Early on in the year, when the children would explain their thinking, I accepted any format of their ideas.  By now, I expect them to use phrases like.."Our team believes," or "We think," anything that demonstrates that they are using a meta cognitive strategy.

Explore - Day 1

15 minutes

I explain to the children that I have already thought of some different ways for us to test our question concerning the freshness of our apple.  (I know that a true scientist and even a higher level teacher would allow the students to suggest these ideas themselves, but because time is an issue; I suggest the solutions we will use to investigate). 

Before we begin the investigation, I remind the students about the lesson we had back in the beginning of the school year about safety in science. I explain that we are going to be using some solutions that I want to make sure will not cause any problems for anyone.  I ask them if they can remember an item that a scientist sometimes will use when they want to protect their eyes.  Of course, they all remember the safety goggles.  I bring out the goggles we will use for our investigation.  

I ask my team leaders to come to the table where I have the materials ready and prepared. I instruct them to take those materials back to their teams and place them in the center of their tables.  

I explain that when a scientist wants to test a question, they have to keep one idea (controlled variable) the same and the other ideas (manipulated variables) different.  This is really the beginning of learning about controlled and manipulated variables.  I really do not want to dwell on this too much, but really want to build this language into the children's speaking vocabularies.  This will provide the basis they will need for later learning.  

After explaining this idea, I ask, "If we know about keeping one thing the same and changing everything else, what will be the one thing we will keep the same?"  The children know right away that it is the apple slice that will stay the same.  Even if they are not certain about that, they can see that the apple slice will be the constant because they have four of them sitting in the middle of their team.

I describe how we will use four different variables that we will test on our apple slices to test our question.  

Before beginning the investigation, I have taken small cups that I have put a small amount of each of the four variables (vinegar, lemon juice, water, and baking soda) in.  I show the students the small eye droppers and tiny scooping spoons I have included on their working tray.  

I describe the process and what my expectations are for each team and team leader.  The team leader is be in charge of the materials and help their team mates to work with the materials.  One person needs to use the eye dropper and the lemon juice, vinegar and water.  They need to be careful to only squirt one shaft full of the liquids onto their apples.  

Again, I explain to the children that this is another one of those things we can control if we all use the same amount. It will help us when we compare our results later.  

Another student needs to be in charge of using one scoopful of baking soda on the apple slice.  I instruct the children to begin setting up and putting all their pieces into place so that we can begin our investigation.  Be sure to explain to the children that when they are putting their solutions on the apple slices to not mix any of the solutions.  They will not have the reactions to their work if they do.  It is possible to mix the vinegar and baking soda and have a completely different reaction that will take away from this investigation. 

Once all the pieces have been put into place, I have the children open their Our Apple Research (student version) and turn to page six.  I also have page six in the teacher version on the screen for the students who need to see the larger picture of what I am explaining.  I also use my Our Apple Research (teacher version) to model what I want them to do.  

I ask them to make an observation of each solution sample covering the apple slice and write a prediction of what they believe will happen to the sample.  I also explain that they are not seeing any reactions because sometimes it takes a while for the reaction to take place.  This offers enough time for the children to write their predictions and not feel a hurried feeling in the investigation. 

Explain - Day 2

20 minutes

On day 2, when the students come into class, the first thing they want to see is what has happened over night to the apple slices.  

There is so much excitement.  

The first thing is to settle the kids down. We get our goggles out and begin examining the samples.  It is obvious to the children that there have been some transformations.  Not only are the transformations evident by sight, but also by smell.  The vinegar and lemon juice are very strong when you walk into the classroom.  After sitting in the room over night, you can really smell the aromas of each solution.  This definitely helps to explain to students the use of their senses.  

I ask the students to get out their research booklets and I bring mine up on the screen as well.  I point out that now that we have had reaction to the solutions, it is important to document what we observe.  This includes not only what we see, but what we smell as well.  

The children cannot wait to get to their writing.  The classroom is quiet and there is a lot of work happening. 

Evaluate - Day 2

20 minutes

After all the writing has been completed, we have discussions about what we observed.  I again bring the original question to the students.  Now that we have investigated the different solutions, which one will be the best for the Crunch Pak company to use in testing their apple slices to sell?  

Everyone collectively says, "the lemon juice." 

It is obvious that the lemon juice is the one to make a difference.  

When I probe more, I ask, "How can you tell that the lemon juice is the best solution?" 

Answers are simple, "It is the prettiest looking apple. It still looks just like when we sliced it yesterday." 

I probe further and see what observations the children make about the other solutions as well.  They notice that the water and vinegar apple slice has swelled up and looks distorted.  The baking soda is crusty and at times, won't even move from the container.  Almost as if it is glued into the cup.