Endothermic reaction: very, VERY cool.

MrBellScience

26 Jan 201202:40

Summary

TLDRIn this experiment, the presenter combines barium hydroxide with ammonium chloride to demonstrate an endothermic reaction. As they mix the chemicals, the reaction absorbs heat, becoming cold enough to freeze water on a wooden block. The process also releases ammonia, producing a pungent smell. The presenter notes the dramatic temperature drop, which is measured to be below zero, and observes ice crystals forming. Despite the cold, the reaction remains subtle but visually interesting, engaging viewers with its scientific and sensory effects.

Takeaways

🧪 The speaker is mixing barium hydroxide and ammonium chloride to demonstrate an endothermic reaction.
🥶 The reaction is expected to absorb heat, making it endothermic, rather than releasing heat as in an exothermic reaction.
🧊 The speaker wets a wooden block to show how cold the reaction will become, indicating the heat being absorbed from the environment.
🧉 The barium hydroxide and ammonium chloride mix together, transitioning from solid powders to a liquid state.
😷 The reaction releases ammonia gas, which the speaker notices by the strong, unpleasant smell.
❄️ As the reaction progresses, the mixture gets very cold, cold enough to freeze the water onto the bottom of the wooden block.
📉 The temperature drops quickly, reaching below zero degrees Celsius, as observed using a thermometer calibrated to minus 10°C.
🌡️ The thermometer reads minus 5°C at one point, confirming that significant heat is being absorbed by the reaction.
❄️ Ice crystals start forming on the sides due to the low temperature.
🚫 The speaker warns against touching the mixture, as it might freeze skin if touched.

Q & A

What are the two chemicals mentioned in the experiment?
-The two chemicals mentioned are barium hydroxide and ammonium chloride.
What type of reaction is being demonstrated in the experiment?
-The experiment is demonstrating an endothermic reaction.
Why does the speaker mention a wooden block being made wet?
-The speaker wets the wooden block to show how much heat the reaction is taking in by freezing the water onto the block.
What product is formed from the reaction between barium hydroxide and ammonium chloride?
-One of the products formed in the reaction is water, which causes the mixture to change consistency and become more liquid.
What gas is released during the reaction, and why does the speaker comment on its smell?
-Ammonia gas is released during the reaction, and the speaker comments on its unpleasant, tangy smell.
What temperature does the reaction reach, according to the speaker?
-The reaction drops below freezing, reaching around -5°C, as indicated by the thermometer.
What physical effect does the endothermic reaction have on the water at the base of the beaker?
-The reaction absorbs so much heat that the water freezes and sticks to the bottom of the beaker.
Why does the speaker say that the reaction is ‘pretty cool’?
-The speaker is impressed by the fact that the reaction absorbed enough heat to freeze the water at the bottom of the beaker, making the reaction visually and scientifically interesting.
What safety precautions does the speaker mention during the experiment?
-The speaker mentions using hand sanitizer after chopping hearts earlier, indicating awareness of cleanliness and safety during experiments.
Why does the speaker express concern about ammonia during the experiment?
-The speaker forgot that ammonia would be released, accidentally inhaling it, and commented on its strong, unpleasant smell.

Outlines

00:00

🔬 Mixing Barium Hydroxide and Ammonium Chloride for an Endothermic Reaction

The presenter begins by introducing barium hydroxide, which will be mixed with ammonium chloride to observe an endothermic reaction. They explain that they will use a beaker instead of another tool because it is more practical. The goal of the demonstration is to show how the reaction absorbs heat from its surroundings.

🧼 Discussing Hand Sanitizer and the Setup for the Experiment

The presenter briefly digresses to mention hand sanitizer on their desk, explaining that it is needed after handling hearts, possibly in a previous experiment. They prepare to demonstrate the endothermic reaction by wetting a wooden block to show how much heat the reaction absorbs from the surroundings.

⚗️ Mixing the Chemicals and Observing the Reaction

The chemicals (barium hydroxide and ammonium chloride) are mixed together, and the presenter discusses the reaction, hoping it will be endothermic and not exothermic. As they combine the substances, the consistency changes, producing water, and the solid powders begin turning into liquid.

😷 Ammonia Release and Observing the Cold Reaction

The presenter comments on the release of ammonia from the reaction, which has a strong and unpleasant smell. They accidentally inhale some of the fumes, explaining that the smell is ammonia, which is often associated with the odor of urine. The reaction is now making the mixture cold.

❄️ Freezing Water with the Endothermic Reaction

As the reaction progresses, the presenter notices the temperature dropping significantly, to the point where the water placed on the wooden block is frozen. The reaction has absorbed so much energy from its surroundings that it causes the water to freeze. The presenter checks the temperature, which drops to below freezing.

🌡️ Measuring Temperature and Further Cooling

The presenter checks the temperature using a thermometer, confirming that it has dropped to below zero. The thermometer reads approximately -5°C and continues to drop. Ice crystals begin to form on the sides of the container, and the presenter notes that if touched, the cold surface could freeze their fingers.

Mindmap

Keywords

💡Barium Hydroxide

Barium hydroxide is a chemical compound used in the experiment shown in the video. It is mixed with ammonium chloride to produce an endothermic reaction. In the context of the video, barium hydroxide is a key reactant whose properties allow the temperature of the surroundings to drop as the reaction progresses.

💡Ammonium Chloride

Ammonium chloride is a white crystalline salt that is another key reactant in the experiment. When mixed with barium hydroxide, it triggers the endothermic reaction, which absorbs heat from the environment. The script mentions ammonium chloride as part of the reaction producing ammonia, a noticeable byproduct with a pungent odor.

💡Endothermic Reaction

An endothermic reaction is a type of chemical reaction that absorbs heat from its surroundings. In the video, the presenter mixes barium hydroxide with ammonium chloride, leading to a decrease in temperature as heat is absorbed, which is demonstrated by freezing water at the base of a beaker.

💡Exothermic Reaction

Exothermic reactions are reactions that release heat. Although the video focuses on an endothermic reaction, the presenter mentions exothermic reactions as a contrast, highlighting that the goal is to show a reaction that absorbs rather than releases energy.

💡Ammonia

Ammonia is a byproduct of the reaction between barium hydroxide and ammonium chloride. It has a distinct, pungent odor that the presenter notes, commenting on its sharp smell in the air. The release of ammonia is a notable aspect of the reaction’s chemical products.

💡Reaction Products

The products of the reaction in the video include water and ammonia. The reaction causes the barium hydroxide and ammonium chloride mixture to change in consistency, from solid powders to a liquid state, indicating the formation of new chemical products.

💡Freezing

Freezing is used to demonstrate the endothermic nature of the reaction. The presenter wets a wooden block and places it under the reaction beaker, showing that the drop in temperature causes the water to freeze, illustrating how much heat the reaction absorbs.

💡Thermometer

A thermometer is introduced towards the end of the video to measure the temperature drop resulting from the reaction. It shows the temperature falling below zero, confirming the cooling effect of the endothermic reaction.

💡Ammonium Chloride Smell

The smell of ammonia, a byproduct of the reaction, is mentioned several times as a strong, unpleasant odor. This demonstrates the chemical change taking place, as the ammonium chloride breaks down to release ammonia gas during the reaction.

💡Energy Absorption

Energy absorption is central to the concept of an endothermic reaction, where heat is drawn from the surroundings. In the video, the reaction between barium hydroxide and ammonium chloride absorbs so much heat that the surrounding water freezes, demonstrating significant energy absorption.

Highlights

Introduction of barium hydroxide and ammonium chloride for an endothermic reaction.

The experiment involves mixing barium hydroxide and ammonium chloride to observe the temperature drop.

The demonstrator explains that the reaction should be endothermic, subtly taking in heat instead of releasing it.

Observation that one of the products of the reaction is water, leading to the mixture turning from solid to liquid.

Ammonium chloride gives off ammonia, creating a distinctive smell in the process.

The reaction is described as generating a noticeable cooling effect, making the surroundings colder.

The demonstrator intentionally wets a wooden block to showcase how cold the reaction gets by trying to freeze water on the surface.

The experiment progresses and successfully freezes the water to the wooden block, indicating the significant temperature drop.

The demonstrator checks the temperature with a thermometer calibrated to minus 10°C, which drops below zero, showing the reaction's intensity.

Observation that ice crystals are forming on the side, confirming the cooling effect of the reaction.

Ammonia produced by the reaction creates a pungent odor, which is noticeable to the demonstrator.

The demonstrator humorously notes the danger of freezing fingers to the frozen surface, highlighting the reaction's cooling strength.

The physical consistency of the mixture changes from solid to liquid as water is produced in the reaction.

The demonstrator points out how the reaction absorbs heat from the environment, effectively demonstrating the principles of an endothermic reaction.

Ice begins to form on the wooden block, further illustrating the extent to which the reaction pulls energy from its surroundings.