Before you read the activity, print out the Chemical Equations Worksheet so that you can refer to it as Staci explains how to use it!

From our science mom:

Recently, my son found a song about the periodic table on YouTube.  He watched it repeatedly and then followed it up with episodes about Chemistry on YouTube from CrashCourse.  I wanted to think of something I could do with him for our Science Saturdays that expanded on the topics he was learning.  I came up with an idea to balance chemical equations using Lego bricks.  I thought using Lego Bricks as manipulatives would make the concept more concrete and easier to grasp, and also because we have eleventy billion Lego bricks scattered in all the corners of our home.  If you don’t have many Lego bricks of many colors readily available, mathlink cubes could be another good option.  We own several molecular modeling kits, but there aren’t as many different color atoms available in these kits and the bonds are often difficult to manipulate.

I started by creating 20 equations for my son to solve.  I made equations with “chemical symbols” that referred to the color Lego he should use rather than actual chemical symbol to avoid unnecessary confusion.  We then gathered around 8 blocks each of 5 different color Lego bricks (white, blue, green, yellow, and red).  We started our activity by talking about a key concept: Conservation of Matter.  The Law of the Conservation of Matter states that the mass of a system must remain constant over time in a closed system.  In reference to balancing chemical equations, this means that the number of atoms of reactants must equal the number of atoms in the product.  Or as we said “what goes in, must come out”.  We also needed to understand the way that chemical formulas are written.  When a number is written in subscript it shows the quantity of atoms of the element it immediately follows.  When a number is written in front of a molecule it applies to all the atoms in the molecule.  For example: H2 shows 1 molecule of 2 hydrogens bonded together, while 2NaCl shows 2 separate molecules of Na bonded to Cl, or 2 Na atoms and 2 Cl atoms in total.

Next, we talked about how we would begin to solve the equations.  My son solved the first 5 or so equations entirely using the Lego bricks.  He began by assembling one molecule of each reactant and then breaking them down to form the molecules of the products.  He quickly observed that sometimes more molecules of reactants would need to be present in order to form the different molecules of product and sometimes there would be leftover atoms that would need to find a home in the equation, perhaps by increasing the number of molecules of product. Using the Lego bricks he was able to visualize where all the atoms were going and where they came from.   

Starting with the 6th equation, he decided he wanted to try to balance the equation using math and then check it with the Lego bricks.  If you are unfamiliar with solving chemical equations, the easiest way is to start by counting the number of atoms in the reactant(s) (the left side of the equation) and then counting the number of atoms in the product(s) (the right side of the equation).  Compare the number of atoms of each element in the reactant(s) to the number of atoms of each element in the product(s).  If the number of atoms are unequal, you next must find the simplest way to equalize them on both sides of the equation.  If you have more than one element to balance, solve for the element that only appears in one molecule of reactant and one molecule of product first.  Add coefficients as needed based on this element and then recalculate the other elements in the other molecules of the equation.  Continue this process until you have balanced your equation.  I was surprised how quickly my son was able to figure out the math of this process and I was impressed when he began to see patterns forming that helped him solve the equations even more quickly.  He gave up checking the equations with Lego bricks about 10 equations into our exercise.

After finishing the 20 equations I had written out for him, he expressed an interest in balancing equations using real chemical symbols that make up real molecules.  I made a short list of 5 equations just for him to try out.  He was able to transfer the knowledge he used with our made up chemical equations to real world equations very easily.  And as a bonus, this gave us a chance to practice identifying elements by their chemical symbol and also the nomenclature of molecules.  

After spending so much time doing math and worksheets, I thought it might be fun to see a chemical equation in action!  I wrote the equation for the reaction of baking soda and vinegar and asked my son if he recognized any of the molecules and asked him if it was a balanced equation as written.

NaHCO3 + CH3COOH → CO2 + Na+ + H2O + CH3COO-

Note:  Vinegar is a mixture of many different chemicals.  It is typically 5% acetic acid dissolved in water, so the molecular formula for acetic acid is used in this equation.

This equation is balanced as written, but we wondered how we could prove that the equation is an accurate description of what took place.  Usually we play with baking soda and vinegar in a way that will result in an uncontrolled eruption, but this time we wanted a smaller reaction that we could observe more closely.  We combined a small amount baking soda and vinegar in resealable sandwich bag, and sealed it up to watch the bubbling reaction.  What happens to the bag as the reaction takes place?  How could you test the contents of the bag to validate the chemical equation?  (Hint: O2 is necessary for flame, H2 causes an explosive pop of flame, CO2 will extinguish a flame)

We really enjoyed this activity.  I initially worried that it might be a little advanced for my 8 year old son, but he surprised me with his enthusiasm and quick comprehension.  A few days after we did this activity, I found a Lego “molecule” sitting on the dining room table with a legend defining Lego brick color to chemical symbol and the instructions to solve his Lego molecule’s chemical formula.  I love when enthusiasm for learning something new is carried over into playtime on his own, it makes these activities worth it!

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The book Everyday Physical Science Experiments With Magnetism by Amy French Merrill is a very easy to read book that explains how to do many classic and simple activities designed to introduce your child to magnetism. After doing these activities, look for more books at your library to go more in depth with the topic. Additional book suggestions are at the end of this post.

Disclosure: This post contains Amazon affiliate links. If you make a purchase from Amazon, I receive a small fee at no extra cost to you.

To complete the activities we needed to purchase two items:

 Alnico Bar Magnets

Iron Filings

Using the directions from the book, my boys separated iron filings from garlic salt, witnessed magnetic field, and so much more! The instructions were so easy to follow and the activities held the attention of both of my boys, aged 4 and 9 at the time. Here’s a look at some of the things we did:

Magnetic Field

Separating Iron Filings

After we did the activities in this book, we decided to make our own Lego car that we powered by magnets.

Lego Car

First, the boys figured out how long the magnet was.

They hid the magnet inside the vehicle.

They continued building the car.

Finished!

Using the invisible force of magnetism, the boys drove the car.

Further your child’s study on magnetism with these books and products:

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Fourth grade standards focus a lot on Native Americans and California mission history. Santa Barbara was the perfect place for my son to learn about these topics. When teaching social studies it is best to use primary sources as much as possible. Primary sources would be actual artifacts or documents from the point in history one is studying. A textbook is written through the eyes of the author and often through a particular cultural lens or even viewpoint of a company or organization. It’s best for my child to see these things for himself and draw his own conclusions. Obviously, he cannot go back in time to witness this history.  Visiting the historical sites and seeing real artifacts is the closest he can get. Naturally, we read books on the subjects and had projects related to the information so that he could delve deeper into the subject and synthesize what he had seen and read.

Santa Barbara has a lot to offer.  We had to narrow it down because we only had a four day weekend and of course one of those days was taken up with the marathon.  Another factor was the budget. Hotels are not cheap in Santa Barbara so we chose carefully about what to do when we were there, hoping not to go broke.  Even if you have a short amount of time and a limited budget you can still have a fantastic educational trip! I’ll share with you what we did.

Chumash Painted Cave

The Chumash Indians are one of the most studied tribes in our area.  After reading many books about the Chumash Indians, we were excited to go this cave where paintings that they created are still there! You will see their actual paintings, how cool is that? They are blocked off with bars so you cannot touch them, but it is very visible.  To get to the park, you have to drive up a big mountain.  My kids marveled at the view and commented on how it looked like we were above the clouds.

Just a couple of days ago we were talking about our trip and my kids were guessing how the Chumash got up there. My boys wondered what was it like to live up high and how the Chumash got food. Because they visited this place, they have a better understanding of the environment that the Chumash lived in. Therefore, they can see why the Chumash developed certain habits or traditions.

This is a California State park so it is free to visit. The constraining factor is parking.  To give you an idea of what the parking is like, see the picture below. You have to find spot on the side of the road that is clear of trees and doesn’t look like you will fall of the edge!  We went early in the morning and had no trouble finding a spot just up the road from the site.

Click here to visit the park’s website. It is not in Santa Barbara, but it is a very reasonable driving distance from it.

Santa Barbara Mission

Twenty one missions were built in California. One of them is right in Santa Barbara. Peek into history by visiting the Santa Barbara mission.  You will see the garden, cemetery, church, and much more.  Your child will have a better understanding of what a mission is by seeing one for him or herself. There is a fee to enter, but parking is free.

For more information on Mission Santa Barbara visit their website: Click here

Goleta Butterful Preserve

Goleta is a short drive from Santa Barbara and is a very special place. It is a stopping point for migrating Monarch butterflies. This is a seasonal event. From November to February you can see the butterflies hanging in the trees resting for the next leg of their migration. At first, they can be hard to see since they have their wings closed and the brown of the outside of the wings blends in with the trees. But, if you look carefully, you will notice them, especially if the begin to flutter their wings.

Pictures were hard to take. The small spot of orange on one of the trees is a butterfly fluttering (picture below). It was hard to discern the butterflies at first, you had to observe carefully. Once you learn how to look for the resting butterflies, it’s amazing to see. It was really interesting to see how they all hung on the branches together.

Not only can your child see migrating Monarchs, the rest of the park provides an exciting landscape to explore.  It’s a natural lesson in geology and biology.

The park is free to enter and parking is free too.  For more information about this park: Click here

Besides, do you really need an excuse to go to Santa Barbara? This place is gorgeous!

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From our science mom, Staci:

I spend a lot of time thinking about science experiments to do with my kids. Sometimes I take the lead from my kids and we explore something they are interested in. Sometimes I introduce new concepts that blow their minds. And sometimes we do things just because I want to see what happens myself! This week’s experiment happened because we had some leftover red cabbage and I wanted to try something I’d never done before.

To prepare for this experiment, I boiled half a head of chopped red cabbage for about 20 minutes and then placed the strained liquid in the refrigerator to cool overnight. The liquid left after boiling red cabbage contains a class of molecules called anthocyanins that will change color based on their environment and can indicate acids and bases. I also made a chart of approximate pH values based on the color of the red cabbage indicator to reference during our experiment.

Red cabbage boiling on the stove

When we were ready to begin our experiment, I asked the kids to think about what type of liquids they would like to test for pH. They talked (argued) about what they would like to test and came up with 10-15 different liquids we could test, such as water, milk, glass cleaner, apple juice, and more. Along with the table of approximate pH values, I made a chart they could fill in over the course of our experiment. The chart had spaces for sample name, cabbage indicator color observation, cabbage indicator pH value, and pH paper value. Before we began to test our samples, I asked my son to predict whether the samples would be acids or bases.

Our samples ready to be tested.

I filled the cups of a mini muffin pan about a third of the way with our test samples. The kids then took turns adding a transfer pipettes full of red cabbage indicator liquid to the samples and recorded their observations. Very dark liquids (such as soda or coffee) were difficult to observe a color change, but overall, this activity was successful and we were able to see very obvious changes of the red cabbage indicator. When all observations had been made, my son used the reference chart I made to assign an approximate pH value to the samples.

Adding red cabbage indicator to test samples

Our finished test samples

Click here to print your own copy of the Red Cabbage Indicator Table

This experiment can end here, but as an extension we wondered how accurate the red cabbage indicator was of pH. I happened to have pH paper, so we were able to obtain a more exact pH value and compare with the observations we made with the red cabbage indicator. If you are interested in purchasing pH paper for your own experimenting, you can find some here: pH paper

I refilled our muffin pan with fresh sample to test with the pH paper. My son then dipped the pH paper in the samples and compared the color result to the color chart on the pH paper container. We finished up this project by filling in our experiment chart and discussing our results.

Completed table

Click here to print your own copy of the pH worksheet

We discussed whether his acid or base predictions were correct and whether red cabbage juice makes a good pH indicator compared to the pH values he observed with pH paper. We discussed which types of liquids gave us the best results with red cabbage juice and hypothesized about what they may have in common. We wondered if the temperature of the red cabbage juice would affect the outcome of this experiment.

This is a fun, easy experiment that you can do at home. My kids had a great time choosing their test samples and have already asked to try this experiment again. My son wants to try all the sodas and all the juices at the grocery store to see the pH range. That may be a bit out of scope for us, but it’s definitely great scientific thinking!

*This post contains affiliate links. I receive a small percentage of the Amazon sale at no extra cost to you.

This post is linked to Montessori Monday:

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On the first day of Fall, I plan to read three fabulous books to my boys.

Mouse’s First Fall by Lauren Thompson is geared to younger kids. Mouse excitedly runs and jumps in the leaves as Minka (another mouse) shows him all the beautiful shapes and colors of the fall leaves.  This book is perfect for young ones just discovering the beauty of the changing season.

Fletcher and The Falling Leaves by Julia Rawlinson is my new favorite book.  Rawlinson is a fabulous descriptive writer.  You can feel Fletcher’s concern and love for this tree as he desperately tries to help the tree keep its leaves.  It ends with a beautiful winter scene that shows Fletcher that the tree was preparing for a new season and that the tree will be ok without its leaves.  As much as we will read this book for enjoyment, it is also a wonderful mentor text for older children learning to write using vivid descriptions, precise verbs, and well developed characters.  I got this book at the library, but I am definitely purchasing this one to keep in our collection at home.

To add a bit of whimsy and humor to our day, we will also read Fall Mixed Up by Bob Raczka.  This story takes all the aspects of fall and switched them around.  For example, a bear is finding nuts and the geese are hibernating!  Your kids may a get a chuckle out of this one. They can “fix” the mix ups by correcting the silly sentences with true ones as you read.  It may even inspire your little ones to write their own silly story or poem.

We are a very science oriented family, so naturally we have to do a little bit of Fall science.  We read the book Why Do Leaves Change Color by Betsy Maestro already, so on the first day of Fall we will explore the colors and pigments found in leaves.  I found a fabulous website with many photosynthesis experiments and demonstrations.  Click here for the link to Seattle Pi where I found our latest science fun.  The demonstration we will do is under the heading, “Photosynthesis and Pigments”.  Using rubbing alcohol and white coffee filters your kids can see all the colors that are inside a leaf that we normally don’t see until the diminishing light of Fall and lower temperatures break down the chlorophyll.  Not only can your kids learn about leaf pigments with this demonstration, they are also learning about chromatography!

Getting our supplies ready

Happy First Day of Fall!

This post contains affiliate links.

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This post contains affiliate links. If you purchase a book from the Amazon link, I receive a small portion of the sale at no additional cost to you.

For our nightly read aloud, I read Insect Invaders to both of my boys, age 4 and 9.  It turned out to be the perfect companion to my son’s study on food chains and ecosystems.  In the story, we follow the students as they search for two missing ladybugs and a spider.  Along the way, there is tons of information about predator and prey relationships on top of the abundant information about insects and spiders.  After learning so much about insects, ladybugs especially, I decided to have my boys create their own ladybug to reinforce some of the concepts learned in the book. I also used this opportunity to assess my oldest son’s knowledge of circles.  If your child is unfamiliar with the parts of a circle or the formulas for finding area and circumference, you could use this activity to introduce some of those concepts.

Here’s what we made:

Four year old artwork on the left!

I like to be realistic in my posts.  I could attempt to create a perfectly created, pinterest-worthy ladybug to dazzle you with, but not that’s not real life. I’d much rather show you a finished product made by kids to set realistic expectations.

Materials used:

• paper plate
• black and red paint
• pipe cleaners
• paper fasteners
• cardboard
• computer paper
• string and yardstick for measuring (optional)
• pencil

Steps we took:

To start, we needed to set up the body parts that needed to be painted. The paper plate would be the ladybugs body and the cardboard would be the ladybug’s elytra (wing covers).  In the story we learned that ladybugs protect their delicate wings with their elytra.  To show that the elytra protects the wings we decided to use cardboard for the elytra and the computer paper for wings.  The stronger material (cardboard) had to fit over the weaker material (paper). We needed to figure out how big to cut our cardboard and paper before we could paint.

To do this we could have easily traced the circle on the paper plate onto the cardboard, but I wanted use this project to asses my nine year old’s knowledge of circles.  We did things in a more complicated manner so I could gain this information. I asked him how big the circle was so that we can make the same size circle on the paper.  To find this out, he said we would need to measure the circle.  “How do you measure something round?”, I asked. This could lead to many different responses.  For us, it led to measuring the circle with string, cutting the string, and measuring the string with a yardstick.

After he read the yardstick,  I asked what part of the circle he just measured.  He told me that he measured the circumference. At this point I also asked him if he remembered the equation for finding the circumference of a circle.  These questions allowed me to see what my son remembered about circles.

Realizing that it would be very hard to reform the string onto the cardboard accurately, this was a dead end for us.  Plan B was to find the radius of the circle. My son found the radius of the circle and cut a piece of string the same size of the radius.  Holding one end of the string on the center point of the cardboard and the other end by the tip of the pencil, essentially making a homemade compass, he rotated around the center point to create a new circle.  In theory, this circle should have been the same size as the original circle on the plate. In reality, due to error in holding the string, the circle was not actually the same size.  All of this is ok and part of the process of learning.  Next time we need to make a circle I will introduce a compass to my son.  After this experience, he can relate the purpose of a real compass to our homemade attempt at a compass.  He will hopefully see why the tool is necessary and more reliable.

Once we had our cardboard circle for the elytra, the boys traced the cardboard circle onto the paper to create the wings.  Our body preparation was complete.  Now, they could paint!  They painted the upside down plate black for the body and the cardboard circle red.  As my nine year old painted to cardboard circle I asked him what part of the circle he was painting.  He told me it was the area. I then asked him what the formula for the area of a circle is. My informal math assessment was complete;  I had a good understanding of my son’s knowledge of circles.  If your child is new to the concept, you could change the assessment aspect of the craft to more of a teaching activity demonstrating the different parts of a circle as they work.

The paint dried overnight and we returned to our craft.  The boys cut the cardboard and paper circle in half.  I punched a hole in the top of the cardboard, paper, and plate so that all three could be attached together using a paper fastener. The wings and elytra were finished.  Both boys put antennae on the ladybug. My four year old happily put on six legs and wing spots just as we learned in the book. My nine year old left his ladybug legless and spotless. Ladybug spots are symmetrical.  Even though, my none year old did not put spots on his, we still discussed this.

Adding to this, my four year played with ladybug, acting out things he learned from the book.  He was pretending to feed the ladybug aphids using matchbox cars!  When one of the wing covers fell off, he first called it the wing, thought for a second, and corrected himself.  Creating this project definitely helped him learn some of the important body parts of the ladybug.

To summarize the concepts learned or reinforced by creating this project:

1. Insects have 6 legs
2. Ladybugs, like many insects, have antennea
3. Ladybugs have protective wing covers called elytra
4. Ladybugs eat aphids
5. Parts of a circle- radius, diameter, circumference
6. Pi
7. Formulas: Area of a circle & Circumference
8. Symmetry

We started with a book, created our own ladybug, then read three more books about ladybugs to add to our learning.  All of the books we read can be related back to the concrete object we made– our ladybug!

Our additional reading:

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The following books are perfect for a study on ecosystems, food chains, food webs, animals, or any nature study!

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Horseshoe Crabs and Shorebirds by Victoria Crenson

This story follows the lives of horseshoe crabs in the Delaware Bay.  When they lay their eggs on the sandy beach, the reader sees just how many birds depend on those eggs for sustenance!  Many types of birds compete for the eggs and fish in the shallow water find the eggs to eat.  This in turn helps other predators, a falcon grabs a smaller feasting bird and a blue heron caught a minnow attracted by the feast of eggs.  Even in death, the horseshoe crab is providing for others as gulls, mice, and flies eat its remains.  The reader can see how this species plays a huge part in the food web of the ocean ecosystem in which it belongs.  They are essential to the survival of migratory birds making a long trip to the Arctic.  The author ends by showing us the eggs that survived  hatching into new horseshoe crabs.  The circle of life continues.

A Log’s Life by Wendy Pfeffer

This story opens with lots of activity going on in an oak tree, from squirrels to slugs this tree is bustling with life!  Once lightning strikes, a huge log falls from the tree.  The log now becomes shelter for many insects, a porcupine, and a salamander.  Decaying material is eaten by insects.  Eventually, rot takes over and the tree become soil with the help of earthworms. An acorn falls, which a squirrel buries right in this new rich soil that was once the oak tree.

The Wolves are Back by Jean Craighead George

In 1926 all the wolves that lived in Yellowstone National Park were gone. In 1995, ten Canadian wolves were brought to the Yellowstone habitat.  With their return, we see how the delicate balance of the ecosystem is restored.   Through the author’s words, the reader sees how important the wolves are and how they directly and indirectly affect life at Yellowstone.  The book is beautifully written.  My attempt at a summary wouldn’t do it justice!  You have to read this one to see how artfully the author conveys the importance of these animals.

One Day in the Tropical Rainforest by Jean Craighead George

Written by the same author as The Wolves are Back, this is the only chapter book on my list.  While the book shows many aspects of the tropical rainforest ecosystem, there are clear examples of how one species affects the others in its environment.  One of my favorite parts of the book is the description of the sloth as “an apartment house”. Covered in algae and home to more than ninety creatures, a sloth is an ecosystem of its own!  If you like this book, there are more in the series.

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You Can’t Smell a Flower With Your Ear by Joanna Cole

We read this book before bed one night and my kids really liked it.  It had a couple of “try this” activities in it which the boys enjoyed.  While my nine year old knew the information, my four year old learned a lot about his five senses. A couple days later we went to our local Botanic Gardens where they have this awesome Sensory Garden.  It was the perfect place the kids to explore their five senses.

The Garden:

The key:

The signs that guide us:

There wasn’t a plant for us to eat, but we did sit on a bench in the garden and eat our snack.  Right next to us was a water feature that allowed to to hear the sound of running water. We sat and listened to the sounds of the gardens, which was mostly birds and the water fountain.

You don’t have to have a specific Garden of the Senses to explore your five senses.  You can do it anywhere! If you want to make this an official lesson have the kids record what they saw, felt, touched, tasted, and heard to see if they can categorize what they experienced.

Or better yet, have them create their own sensory garden!  Have the children brainstorm what they would put into a sensory garden. Then, they can decide what kinds of things would put into the garden to stimulate all five senses. If they are old enough, they can draw a blueprint of the garden. If you have enough space, plant the garden at your home or school.  Your children can even make their own version of the signs and key

We really enjoyed the Garden of the Senses, but look what else the rest of the Botanical Garden had for us:

Click to see any of the pictures larger!

Do you see the butterfly?

My four year finding bugs. We saw a cool centipede!

If your looking to teach your little one all about their five senses, read the book then take a fabulous walk in a beautiful setting and talk about how you are using your senses!! I always love combining a book and real life experience

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I started doing Science Saturdays with my son the spring before his fifth birthday.  We tried to think of something fun and interesting to do every weekend.  From the very beginning it was important to me that we followed the scientific method and kept a lab notebook.  At the time, my son was just beginning to learn to write, he often asked how to spell things and spent a lot of time drawing pictures of his observations and dictating to me his conclusions. He has graduated to writing his own hypothesis, adding sentences to his observations and writing his own conclusions.  Now that my almost 3 year old has joined our science fun, we spend a lot of time drawing pictures of our set-ups and observations again.  If you are introducing your children to science, don’t be afraid to encourage the use of a lab notebook, no matter their ages.  They may surprise you with their observations and attention to detail!

Teaching the scientific method can seem like a daunting task, especially if you are teaching young children. The good news is that you are probably already following the process without even thinking about it.  Adding the vocabulary of the scientific method during your experiments can encourage critical thinking and reasoning skills.

Observation:  about what can you use your senses to ask a question.

Question: the why, what, or how you want to know about what you are interested.

Hypothesis: a guess about why or how something happens.

Prediction: how can you test your hypothesis and what will happen if…

Testing: conduct your experiment.  Sometimes this will lead to more questions and more testing.

Conclusions:  what have you learned from your testing.

Communicate:  tell others what you have discovered so they can learn more.

Not every step of the scientific method needs to be recorded in your notebook, but we are sure to include a few sections.  Specifically, we write a question about our experiment to highlight the purpose of the experiment.  Next we make and write a hypothesis about our experiment.  We take careful notes and draw figures of our observations.  And finally, we write a conclusion about what we have learned from our data.  Sometimes we also include questions that we thought about while learning the answers to other questions.  We call that the Circle of Science!

Does your family consider the scientific method when you are doing at home experiments?  My son’s lab notebook is a childhood memento that I treasure.  I can’t wait to keep filling it’s pages with our science fun and I hope your family can find just as much enjoyment in your own lab notebooks as we do.

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Oceanography Week 2:  Salinity Part One

From our science mom:

Salinity is defined as the salt content dissolved in water and is important in determining both chemical and physical characteristics of water, such as density and heat capacity.  This week we wondered if ocean salt water behaves differently than our water from the tap at home.  Specifically, my son wondered which water would freeze first and if the waters would heat up at different rates.

To begin, we needed to make up a salt water solution.  We learned the average salinity of the oceans is 3.5% by looking it up on Google.  A 3.5% solution is 3.5 g solute in 100 ml of solvent.  We made 1L of our salt water solution by dissolving 35 grams of table salt into 1 L of tap water.

I asked my son to make a hypothesis about which solution would freeze first and why he thought that.  Using a measuring cup and identical cups, we poured water into our containers and placed them in the freezer.  We were sure to carefully note which color container held which solution in our lab notebook.  We set a timer for 15 minutes and continued to check on the containers periodically.  Which container of water began to freeze first?  How does your hypothesis compare with your observations?  What conclusions about properties of salt water can you make?

After making and recording our observations, we set out to learn the whys and hows to our data.    Both salt water and fresh water will freeze, but salt water freezes at a lower temperature. According to the National Oceanic and Atmospheric Administration (NOAA), fresh water freezes at a temperature of 0 degrees celsius, while salt water freezes at -2 degrees celsius.  The lower freezing point is due to the salt crystals disrupting the ideal crystal forming lattice that water prefers.  In order to form an ice cube, the motion of the water molecule has to be restricted in a very specific crystal structure.  When you add salt to the water, both the water molecules and the salt molecules must be restricted, which is much harder to do and this lowers the freezing temperature. Interestingly, when you have an unsaturated salt water solution, the water will begin to freeze at the top and push the salt crystals into the remaining liquid.  Because of this property, sea ice can be melted into drinking water.

If you want to take your science outside, try taking your frozen cups of salt water and tap water out to melt.  Do they melt at the same time?

The second part of our experiment explored whether salt water and tap water heated up at different rates.  After making a hypothesis, we measured equal amount of water into similar cups and attached thermometers.  We placed the cups in a sunny spot outside and took the starting temperature and continued to monitor the temperature of the waters every 30 minutes.  My son took careful notes and recorded the temperature for a few hours.  What were your observations?  Was there a difference in the heating pattern between the two waters?

These were the first two experiments I had planned to explore the salinity of water.  In an upcoming experiment, we will determine how different salt concentrations in water affect the density of water.

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