What Freezes first… Hot or Cold Water? Follow FizzicsEd 150 Science Experiments: Comments 20 You Will Need: One cup of cold water, 100mL in volume One cup of hot water, 100mL in volume One Stopwatch One Stirrer A freezer A pen and paper Copyright Instruction 1 Stir both water cups the same amount of time. Place both cups of water inside your freezer and start the timer. 2 Keep checking at 5 minute intervals to see which freezes first. 3 Record your observations. What happened? 4 Live remote classes with experienced distance educators Discover >30 virtual workshops designed to engage students isolated at home. Direct curriculum links Up to 30 homes can connect together. Live classes – students can question & answer our educators and participate in experiments using household materials Simple connection via one-click connect Based on 10 years of distance education experience & global best practice Multi-award-winning distance classes available to keep up student enthusiasm & enrichment! Why Does This Happen: Hmmmm, you’ve completed an experiment whose results are quite tricky to explain. Did you find that the hot water froze first? Under some conditions this can happen… We started with two containers of water, which were identical in shape and held identical amounts of water. The only difference between the two was that the water in one was at a higher (uniform) temperature than the water in the other. Of course, if the hot water had started at 99.9° C, and the cold water at 0.01° C, then clearly under those circumstances, the initially cooler water would have frozen first. However, under some conditions the initially warmer water will freeze first — if that happens, you have seen the Mpemba effect which describes the phenomenon. How does it work you might ask? Several ideas have been put forward and no-one really is sure as to which effect plays the biggest role: 1. As the initially warmer water cools to the freezer temperature, it may lose significant amounts of water to evaporation. The reduced mass will make it easier for the warmer water to cool and freeze than the colder water. 2. A convection current may have been setup in the warmer water. As the warmer water cooled it lost heat primarily through the surface of the liquid faster than the colder water. This is due to a great temperature difference between the cold freezer air and the warm water. The water from the bottom of the cup then rose to the water surface, bringing more heat energy to the cold freezer air. As the current is greater in the warmer water than the cold water, a greater amount of liquid got exposed to the cold freezer air. Think of a fan forced oven, circulating the hot air through the oven heats the oven faster than just allowing the air to sit still… bakers have known this over a thousand of years! More on temperature and water rising or falling 3. The surrounding air around the cups may have more movement around the warmer cup, therefore drawing heat energy away from the warmer cup more effectively. 4. Warm water holds less dissolved gas than cold water. There have been some suggestions that the presence of dissolved gases impede the production of convection currents in the colder water. 5. The cold water may have supercooled, therefore not forming a solid as quick as the hot water. Quote: “I often put boiling water in the freezer. Then whenever I need boiling water, I simply defrost it.” -Gracie Allen. Variables to test More on variables here What happens if you add salt to the water? Does it make a difference if you change the volume of water? Learn more! From colour changes to slimy science, we’ve got your kitchen chemistry covered! Get in touch with FizzicsEd to find out how we can work with your class. Chemistry Show Years 3 to 6 Maximum 60 students Science Show (NSW & VIC) 60 minutes Online Class Available Read More Enquire Now Magic Crystal Tree Science Kit $3.25 inc. GST View Details Add to Cart STEM Full Day Accelerator - Primary Designed from real classroom experiences, this modular day helps you create consistently effective science learning that directly address the new curriculum with easily accessible and cost-effective materials. Read More Enquire Now Be Amazing! How to teach science, the way primary kids love. $29.95 inc. GST View Details Add to Cart
Stir both water cups the same amount of time. Place both cups of water inside your freezer and start the timer.
Live remote classes with experienced distance educators Discover >30 virtual workshops designed to engage students isolated at home. Direct curriculum links Up to 30 homes can connect together. Live classes – students can question & answer our educators and participate in experiments using household materials Simple connection via one-click connect Based on 10 years of distance education experience & global best practice Multi-award-winning distance classes available to keep up student enthusiasm & enrichment!
From colour changes to slimy science, we’ve got your kitchen chemistry covered! Get in touch with FizzicsEd to find out how we can work with your class.
Chemistry Show Years 3 to 6 Maximum 60 students Science Show (NSW & VIC) 60 minutes Online Class Available Read More Enquire Now
STEM Full Day Accelerator - Primary Designed from real classroom experiences, this modular day helps you create consistently effective science learning that directly address the new curriculum with easily accessible and cost-effective materials. Read More Enquire Now
Designed from real classroom experiences, this modular day helps you create consistently effective science learning that directly address the new curriculum with easily accessible and cost-effective materials.
Be Amazing! How to teach science, the way primary kids love. $29.95 inc. GST View Details Add to Cart
can you please answer these 2 questions: What’s the independent, dependent & controlled variable of this experiment? And what equipments have you used for this experiment? Reply
Hi Rose! The independent variable for this experiment was the temperature of the water (this was the variable that we could manipulate). The dependent variable was the time it took for the water to change from liquid to solid (as this depends on the initial temperature of the water). The controlled variables were the freezer temperature, the cup size, the volume of the water used in each test and the amount of stirring in each cup. More details on variable testing here You can find the details on the materials needed at the top of this page. Have fun with this experiment! Reply
Hi Zach! If the water is close to boiling you really need to be careful. Also, water spills are a slipping hazard. Reply
Its an interesting experiment! Please let us know what your results were… do they conform to the theory above? Have fun! Reply
Hi! Try cups with different amounts of heat – you might find that there is a particular temperature where the result can be opposite 🙂 We like to use near-boiling vs room temperature, but you could try every temperature as a series of tests (as long as you’re safe with water over 55 degrees celsius). Have fun! Reply
This has been a tough one for us to reproduce too! We’ve found that there can be slight differences within the freezer itself, whereby placement of the cups in relation to the vents being a crucial factor. Did you try it again? Reply
wow, this experiment was really surprising at first but now that I have read the science behind it, it makes a lot more sense. Reply
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