Is the ocean like an onion? (CBS talk)

Introduction
Public summary: 

2020 CBS talk about density and ocean mixing.

Useful information
Kit List: 

Large(approx 1x0.5x0.2 m), flat plastic tank (filled with water during experiment)*
Plain paper
Salt
Insulated flasks*
Ice
Food colouring (four colours)*
Plastic cups
Tube with nozzle and attached funnel*
Thermometer*
One(1) raw egg
Balloons (one semi-inflated, one containing water)
Tall, clear plastic/glass vase (full of water)

*borrowed from Department of Earth Sciences

Explanation
Explanation: 

Prepare waters by dissolving appropriate amounts of salt in warm water. Cool waters to room temperature/0 degC using ice. DO NOT allow water to freeze.
Fill tank with room temperate salty water.
Fill cylindrical vase half with salt-saturated water and then top-up with fresh water, trying to prevent the mare mixing - do this just before the start of the talk.

Risk Assessment
Date risk assesment last checked: 
Wed, 05/02/2020
Risk assesment checked by: 
herobain
Date risk assesment double checked: 
Wed, 05/02/2020
Risk assesment double-checked by: 
Beatrix Huissoon
Risk Assessment: 
Demo Hazard Risk Likelihood Severity Overall Mitigation Likelihood Severity Overall
Ocean mixing tank Large, flat tank of water Heavy tank falling over on demonstrators. Large volumes of salt water being spilled. 3 4 12 Place tank on stable table surface. Prevent volunteers in earlier part of the talk from going near the tank. Don’t move tank during talk. 1 4 4
Jet of water coming out of nozzle Demonstrator losing control of nozzle, and spraying the audience. 3 1 6 Use clean/fresh tap water for demo. Don’t operate the nozzle while talking to increase concentration. Have drying cloths on hand, and clean up any spills immediately. 2 1 2
Jet of water coming out of nozzle Water could become introduced into the electronics at the front of the lecture theatre. 3 3 6 Don’t operate the nozzle while talking to increase concentration. Have drying cloths on hand, and clean up any spills immediately. 2 3 6
Ice Cold burns from skin coming into contact with ice - especially in association with salty water. 2 2 4 Wear gloves when handling very cold water/ice. Don’t put hand into water. Dry hands if they do get wet to prevent further chills. Keep ice buckets away from volunteers. 1 2 2
Food colouring Spillage - staining desks. 4 1 4 Keep in a box until needed (out of the way of volunteers).
Be careful, keep food colouring in the box, wipe up spillages with paper towels immediately.
2 1 2
Food colouring Could cause allergic reaction. 2 5 10 Keep in a box until needed (out of the way of volunteers). In case of allergic reaction, call first aider immediately, and allow parent to administer epipen if appropriate. 1 5 5
Magic floating egg Egg Child drops the egg/misses the vase of water leading to mess, slipping over. 3 2 6 Pick a child old enough to not drop egg. Have backup eggs. Clean up any spills immediately. 2 1 2
Egg Child could be allergic and have an anaphylactic shock. 2 5 10 Make clear the volunteer will be holding an egg (so that an allergic child doesn’t get picked). In case of allergic reaction, call first aider immediately, and allow parent to administer epipen if appropriate. 1 5 5
What is density? Balloons Popping and scaring people. Water spillage in case of water-filled balloon. 4 2 8 Don't over-inflate/fill balloon. Keep balloon demo away from electronics. Choose a volunteer old/large enough to hold balloons. Clear up spills immediately. 2 2 4
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