#chemistry experiment

‘Seizure’ an entire apartment covered in beautiful blue Copper Sulphate crystals. By Roger Hiorn

Created by the artist pouring 75000 litres of Copper Sulphate solution into an abandoned London flat, the crystals were left to form on all the surfaces including the bath.

1. Does hot water or cold water freeze faster?

Hypothesis:  If two glasses with ½ cup of cold and hot water respectively are placed into a freezer, then the glass with cold water will take less time to freeze than hot water because it is already closer to freezing temperature.

Controlled Variables:

Amount of water (½ cup)

Glasses

Independent Variable(s):

Original water temp

Dependent Variable(s):

How long the water takes to freeze

Materials:

Water (½ cup for each glass)

2 Glasses (preferably similar if not the exact same sort)

Thermometer

Tape/pen (to label)

Timer/stopwatch

Liquid measuring cup

Freezer

Procedure:

1. Turn sink tap to coldest setting, measure out ½ cup of water and put in a glass

2. Check temperature of water

2a. Record temp

3. Label glass as “Cold”

(CONCURRENTLY)

4. Turn sink tap to hottest setting, measure out ½ cup of water and put in a glass

5. Check temperature of water

5a. Record temp

6. Label glass as “Hot”

7. Put both glasses in the freezer and set a stopwatch, checking in periodically (every 5-10 minutes or so) until a layer of ice covers the entire surface of the water

8. Repeat steps 1-7 two more times

Observation:

Data:

Theory:

According to my data, my hypothesis was correct: it takes longer for hot water to freeze than cold water. However, after doing some research online, I realized that the hot water should have taken less time to freeze than the cold due to the phenomena known as the “Mpemba Effect.” The Mpemba Effect has a few different explanations as to why it happens, but the most compelling to me was that warm water evaporates more rapidly and, since it’s an endothermic process, it cools the water down and freezes it more quickly. One thing I noticed about the hot water freezing that didn’t happen with the cold water in my experiment was the ice crystals on the sides of the glass, indicating that the water had been evaporating and was frozen to the side of the glass which is why this explanation makes sense to me. The Mpemba Effect is also explained by the hydrogen bonds bringing water molecules into close contact, forcing the O-H bonds to stretch and store more energy (This is the website I found: https://medium.com/the-physics-arxiv-blog/why-hot-water-freezes-faster-than-cold-physicists-solve-the-mpemba-effect-d8a2f611e853 )

By Mr. Fluffernutter Ah-ha! Greetings, young adventurers, budding alchemists, and fellow lovers of all things fizzy, glowy, and slightly explosive! It is I, the one and only Mr. Fluffernutter—renowned world explorer, carrot connoisseur, and today’s Head Bunny Chemist! 🐰🧪 Now, most of you know Minecraft as a land of pickaxes, blocky cows, and the occasional unexpected TNT accident (don’t look at…

Homemade indoor fireworks…

Here is a practical example of using the reactivity series. Which metal is more active? Manganese? Or zinc? Which one would replace the other from its solution?

For this experiment I used two test tubes. Zinc chloride solution is added to the first one and manganese chloride to the second one. A piece of manganese is added to the zinc chloride solution and a piece of zinc to the manganese chloride.

As you can see from the reactivity series, manganese comes before zinc, so it should replace zinc in zinc chloride and not vice versa:

K→Ca→Na→Mg→Al→Mn→Zn→Fe→Co→Ni→Sn→Pb→H→Cu→Ag

And indeed, there is nothing happening in the second test tube. But watch the first one...

There is a metallic zinc sediment forming around the piece of magnesium. Perhaps less spectacular than in case of tin or copper. Only visible when magnified. 

Mn (s) + ZnCl2 (aq) → Zn (s) + MnCl2 (aq)

You can also notice some gas bubbles. This is hydrogen formation as a result of a secondary process. Due to hydrolysis of zinc chloride in an aquatic solution, there is an acid environment containing hydrochloric acid. Manganese reacts with the acid which leads to the hydrogen gas release.

Hydrolysis (1st step):  Zn2+ + 2Cl- + HOH ⇄ ZnOH+ + Cl- + H+