We're going to watch how density works by making a simple lava lamp that doesn't need electricity! If you like to watch blob-type shapes shift and ooze around, then this is something you're going to want to experiment with. but don't feel that you have to use the materials mentioned below - feel free to experiment with other liquids you have around the house, and be sure to let me know what you've found in the comment section below.
All you need is about 10 minutes and a few quick items you already have around the house. Are you ready?
[am4show have='p8;p9;p11;p38;p92;p13;p40;p68;p79;' guest_error='Guest error message' user_error='User error message' ] Here's what you need to find:
Fill a water glass halfway with colored water, and add a 1/2" layer of oil on top. Shake salt over the oil layer and watch the lava lamp start to work! You'll see the bottom oil layer move as a salt-oil-drop falls to the bottom of the glass. Over a few minutes, the oil breaks free of the salt and moves back up to rejoin the oil layer on top.
Download Student Worksheet
What's happening? You're actually watching the salt itself fall through the oil. However, the oil sticks to the salt to form a larger object, and since the salt is heavier than oil and water, the whole mess plunks to the bottom of the glass. At the bottom of your cup, the oil breaks free of the salt (eventually) and rises back up. Does it matter if you heat the oil, chill the water, or vice versa? Is there anything that works better than salt?
Going Further: Unscrew the camp and add a broken-up effervescent tablet (like alka-seltzer) to your bottle. Cap it and watch what happens! Did it react with water, oil or both? What if you turn off the lights and shine a flashlight through it? [/am4show]
All you need is about 10 minutes and a few quick items you already have around the house. Are you ready?
[am4show have='p8;p9;p11;p38;p92;p13;p40;p68;p79;' guest_error='Guest error message' user_error='User error message' ] Here's what you need to find:
- empty glass jar with straight sides (if possible)
- vegetable oil
- salt
- water
- food dye
Fill a water glass halfway with colored water, and add a 1/2" layer of oil on top. Shake salt over the oil layer and watch the lava lamp start to work! You'll see the bottom oil layer move as a salt-oil-drop falls to the bottom of the glass. Over a few minutes, the oil breaks free of the salt and moves back up to rejoin the oil layer on top.
Download Student Worksheet
What's happening? You're actually watching the salt itself fall through the oil. However, the oil sticks to the salt to form a larger object, and since the salt is heavier than oil and water, the whole mess plunks to the bottom of the glass. At the bottom of your cup, the oil breaks free of the salt (eventually) and rises back up. Does it matter if you heat the oil, chill the water, or vice versa? Is there anything that works better than salt?
Going Further: Unscrew the camp and add a broken-up effervescent tablet (like alka-seltzer) to your bottle. Cap it and watch what happens! Did it react with water, oil or both? What if you turn off the lights and shine a flashlight through it? [/am4show]
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where is the video
Changing temperature of the oil affects the rate the the salt falls through it. Changing the temperature of the water affects how the salt dissolves into the water.
If the effervescent tablets are small, they are too light and will remain suspended in the oil.
Hi there we tried the cold water and warm oil combinations. What are the differences we are supposed to notice? And if there is a difference to notice, what is the reason for it? Also tried the tablets – what is the reason why the small chunks get stuck in the oil and don’t go down to the water? Thanks in advance for you answers.
No, you’ll need to keep adding more salt!
Does the lava lamp work for a long period of time without a constant supply of new salt?
This experiment is so cool! I’m constantly asking for a lava lamp XD