toddler doing a science experiment

Perfect Preschool Science Fun: Sink or Float!

Two truths: Preschool science is a thing of beauty and preschoolers love to eat snacks.  That makes snack time preschool science experiments a perfect fit for curious little ones.  Little kids get to explore but you don’t really need anything fancier than a normal snack!

Truly, science comes so naturally to children because they spend their entire day learning and exploring through their own natural curiosity.  Little kids are born to be scientists!!!   Their whole lives follow the scientific method that I’ve been teaching older kids for years!  

Even the least scientific among us can do science with little kids.  They are doing it already all on their own! 

Think about it and you can watch science in action at any given time with kids.   This is a preschool version I’ve made of that scientific method.  How often have you seen your child do exactly this cycle?  Probably loads of times!!

preschool science experiment cycle


For example, we went to a new playground this morning.  I watched my 2 year old look at a new obstacle of pretend tree stumps as a way to get down from a platform and could imagine this little thoughts going through this cycle exactly based on his actions!!

Ask a Question:

He tilted his little head to the side obviously thinking about what to do: “Can I do that?” and “Can I reach?”


He must’ve guessed he could make it to the first stump because he grabbed the bars at the opening and started to step out – much to this mama’s worry because it was actually a bit high and I wasn’t sure it was small enough a gap!! 

Experiment & Explore: 

He did a couple little tries first with one foot then the other, but obviously wasn’t as able as he originally thought.

Think About It:

He stopped and looked again (head tilted again – so cute!) because his first idea didn’t work.  It was too far for him to step out and reach.  This usually leads to more questions and the whole things starts again!  In my son’s case his new question must have been “Will it work if I do it backwards on my belly like stairs?” because I had to cut this experiment short by grabbing him instead of letting him dangle over the edge on his belly! Yikes!

Now you just add in a little bit of on purpose experimenting with a few key concepts explained so kids understand and voila – every mom is the most awesome science teacher!

Snack Time Food Science Fun

Maybe as the mom I should say “Don’t play with your food!”, but snack time science experiments really are the perfect opportunity for observing different things because it’s pretty easy to get an assortment of foods to test! The premise of this experiment is SUPER EASY but loads of fun for the kiddos.  You basically do nothing more than you normally would for snack, but it becomes a whole big fun preschool learning activity!  The best kind of mom win! 

And bonus for picky eaters – it makes the food more interesting and might get more eaten – just like this snack time game I wrote about in another post!

Here’s what we used to start this experiment: 

Grapes, marshmallows, sprinkles, cucumber, cheese and white chocolate chips.  A totally random assortment – use whatever you have that is a mixture of heavy and light!!
food for snack time science grapes, cheese, cucumber, marshmallows and sprinkles

The Perfect Preschool Science Experiment:  Sink or Float?!

This is a great preschool or toddler science experiment because it is easy, so many observations and learning can happen, and you can do it over and over and over again, just with different materials!! Pretty sure we do it about every month at least.










Young and Busy Toddler Science Experiment:

Fill a cup with water and just start dropping things in, letting your child explore and have fun with zero structure whatsoever.  100% excellent at this age!! My 2 year old loved it this way – plus eating everything out of the cup! Yes, even the soggy piece of bagel – yuck!toddler science dropping food to sink or float



Preschool Age Science Experiment:











If your kiddo is a little older and/or more willing to slow down and do things one at a time this way is great!  It adds a bit more science on purpose with just a few little prompts from mom.  Again, mom doesn’t need to know any science though! I’ve got some prompts for you, and you can have fun learning together.   Drop foods in the cup of water one at a time and add in some recording of observations and analysis questions. 

Sink or Float Observations:

This is the perfect simple experiment for pretending to be a scientist recording observations.  This is my 4 year old writing an F or S beside each food I sketched.  This also had the huge added bonus of giving her a chance to practise the letter S!  It’s a tricky one that usually ends up backwards and it’s in her name so double win for sneaking that in here! 



You could also just draw an arrow up/down if your child doesn’t write yet.  Or draw a little cup beside each and they just scribble where it ended up – top or bottom!  Easy to fit whatever your child can do or is in the mood to do while playing scientist.      child recording science observations  


Preschool Science Analysis:

It’s the perfect simple toddler experiment for observing something simple, but then getting your toddler to think about WHY something happened!  Instead of just leaving it at yep, it sank or hey look, it floated ask some simple follow up questions!  You don’t need to know the answers.  It’s even more fun to learn together!Cup of water with food sinking and floating experiment

Great Questions to Chat About:

Question: Follow-Up
Why do you think it sinks/floats? Depending on their answer, test the theory! 
Do all big things sink and small things float? – Try a big thing you know will float and a small thing you know will sink so they see it isn’t just about size.  

– Talk about boats – they’re big but don’t sink.

Does the shape make it sink or float? – Try the same item cut in different ways. 

– Try a couple different round things. 

Does how we drop it matter?   – Take the same item and drop it from up high & down low.  

– Drop something with different sides facing down.

Does it always float?  Leave things for a while and see if they absorb water and sink later. 















Preschool Science Experiment Data SheetYou can see based on our questions we ended up adding a few foods to test.

The Science:

Basically, it all comes down to buoyancy.  Is the buoyant force of the water pushing up on the food more than the force of gravity pulling it down?  These forces depend on density of the fluid and mass (therefore density) of the object being tested.   

A lot more complex than a toddler or preschooler needs to know, but if you want to check it out there’s a good simple explanation here.  My kid loves science so we did talk about density in a kid friendly way as some things packing more of what makes it into the same space as other things.  I drew a picture like this to explain it: density diagram




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It may seem ridiculous as far as detail for a 4 year old, I get it.  But since I’m a science teacher and my husband is also a science guy we’ve probably gone a bit overboard haha…I mean, thanks to the book Quantum Physics for Babies my daughter actually knows about atoms making up everything!

Want More Preschool Science??? Bonus Buoyancy Experiment:

1: Fill 3 glasses with water. 

2: Put 4tbsp salt in the first glass, 2 tbsp salt in the second glass and nothing in the third. 

3:  Gently place an egg in each cup and see how the buoyancy is different in each because the density of the water is different in each cup! 

**Spoiler alert** The egg should sink in just water – least dense liquid.  Next, the egg should float in 4tbsp salt as it is most dense and more dense than the egg.  Finally, the egg should half float/half sink about halfway down in the 2tbsp cup.  If the 2tbsp one sinks add more salt.  If it floats too high, add some plain water.

For more snack time fun check out this mystery snack activity!

I hope this makes for a happy moment in your day!  I’d love to see how your experiment goes – tag me in a pic of your sink/float results on facebook @happymomentsmom.  

Want more ideas for happy moments with your kids?

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