This easy to set up salt water density experiment is a cool variation of the classic sink or float experiment. What will happen to the egg in salt water? Will an egg float or sink in salty water? There are so many questions to ask and predictions to make with this easy saltwater density science activity. Make sure to check out all our classic science experiments for more great ideas!
THE DENSITY OF SALT WATER
Get ready to add this simple salt water density experiment to your preschool science lesson plans this season. If you want to learn about why objects float in salt, or maybe they don’t, let’s dig in. While you’re at it, make sure to check out these other fun water experiments.
YOU WILL NEED:
- 2 Tall glasses big enough to hold an ice
- Cold water
SALT WATER DENSITY SET UP:
STEP 1: Start by filling one glass about 2/3 of the way full with water. Ask the kids what will happen if you carefully drop an egg into the glass of water. Now go ahead and do it!
STEP 2: In the other glass, fill to the same height with water. Now stir in 3 tablespoons of salt. Mix well to dissolve the salt! Ask the kids what they think will happen this time and demonstrate!
SALT WATER DENSITY IN THE CLASSROOM
Kids can easily experiment with different objects from around the room. We love sink/float style experiments for encouraging predictions!
Small plastic items will work best with the measurements of salt and water provided. If the item still sinks in the saltwater, ask the kids what they think! Should they add more salt? Have each kid contribute an item to the experiment!
THE SIMPLE SCIENCE OF DENSITY
This is a great experiment to add to your ocean science lesson plans because the ocean is salty!
So many great saltwater density questions:
- Do you float better in salt water?
- What about some of the biggest mammals on earth that float easily in the ocean?
- Does the density of the saltwater play a role?
Why is the ocean salty? The simple answer is that the salt comes from the rocks on the land that has been broken down by erosion and is carries by streams to the ocean.
What is density?
Big items that feel light, like a ping pong ball, we would say are less dense, than smaller items that feel heavy, like a gold ring. When added to water, objects that are denser than water sink and those that are less dense than water float. Hollow things often float too as air is less dense than water.
You can experiment with many objects that sink and float in water, but what happens when you add salt to the water? Can you change whether the object, like the egg, still sinks or not?
How does salt change the density of water?
Adding salt to water makes the water denser. As the salt dissolves in the water, it adds mass (more weight to the water). This makes the water denser and thus allows more objects to float on the surface that would sink in fresh water.
Disclaimer and Safety Precautions
Warning is hereby given that not all Project Ideas are appropriate for all individuals or in all circumstances. Implementation of any Science Project Idea should be undertaken only in appropriate settings and with appropriate parental or other supervision. Reading and following the safety precautions of all materials used in a project is the sole responsibility of each individual. For further information, consult your state’s handbook of Science Safety.
- Put on protective eyewear. Conduct the experiment on the plastic tray and in a well-ventilated area.
- Keep a bowl of water nearby during the experiment.
- Keep flammable materials and hair away from flame.
- Avoid looking directly at burning magnesium to prevent eye discomfort.
- Do not attempt to extinguish the solid fuel and magnesium — let them burn down completely. Do not touch the stove after the experiment — wait until it cools down.
- Do not allow chemicals to come into contact with the eyes or mouth.
- Keep young children, animals and those not wearing eye protection away from the experimental area.
- Store this experimental set out of reach of children under 12 years of age.
- Clean all equipment after use.
- Make sure that all containers are fully closed and properly stored after use.
- Ensure that all empty containers are disposed of properly.
- Do not use any equipment which has not been supplied with the set or recommended in the instructions for use.
- Do not replace foodstuffs in original container. Dispose of immediately.
- In case of eye contact: Wash out eye with plenty of water, holding eye open if necessary. Seek immediate medical advice.
- If swallowed: Wash out mouth with water, drink some fresh water. Do not induce vomiting. Seek immediate medical advice.
- In case of inhalation: Remove person to fresh air.
- In case of skin contact and burns: Wash affected area with plenty of water for at least 10 minutes.
- In case of doubt, seek medical advice without delay. Take the chemical and its container with you.
- In case of injury always seek medical advice.
- The incorrect use of chemicals can cause injury and damage to health. Only carry out those experiments which are listed in the instructions.
- This experimental set is for use only by children over 12 years.
- Because children’s abilities vary so much, even within age groups, supervising adults should exercise discretion as to which experiments are suitable and safe for them. The instructions should enable supervisors to assess any experiment to establish its suitability for a particular child.
- The supervising adult should discuss the warnings and safety information with the child or children before commencing the experiments. Particular attention should be paid to the safe handling of acids, alkalis and flammable liquids.
- The area surrounding the experiment should be kept clear of any obstructions and away from the storage of food. It should be well lit and ventilated and close to a water supply. A solid table with a heat resistant top should be provided
- Substances in non-reclosable packaging should be used up (completely) during the course of one experiment, i.e. after opening the package.
Dispose of the reagents and solid waste together with household garbage.