# Blue/Green (DD-361)

> When aluminum is added to copper sulfate solution with hydrochloric acid, the acid strips aluminum's oxide layer and aluminum displaces copper in a vigorous, heat-releasing reaction. Copper compounds give flames a characteristic blue-green color, because heat excites copper's electrons, which emit specific wavelengths as they relax. The footage shows the reaction and a green flame.

- Department: Science
- First published: 2024-11-04
- Last updated: 2024-11-04
- Permalink: https://detailenjoyer.com/case/blue-green/
- Author: Marcus Easterling (DetailEnjoyer), The Detail Department

## Quick facts

- **DD-361-F01**: Aluminum displaces copper. _(Write-up · Exhibit A (Displacement))_
- **DD-361-F02**: Acid removes aluminum's oxide. _(Write-up · Exhibit B (Acid))_

## Write-up

Copper compounds turn a flame blue-green. Aluminum, copper sulfate and acid set it off.

1. **Displacement**: Aluminum displaces copper.
2. **Acid**: Acid removes aluminum's oxide.
3. **Color**: Copper gives blue-green flames.
4. **Electrons**: Excited electrons emit light.
5. **Heat**: The reaction releases heat.

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## Reel vs. record

- **Note**: The Reel says hydrogen chloride; in solution it is hydrochloric acid.

## Video: Blue/Green: Copper Compounds Turn a Flame Blue-Green

- Duration: 28.1 s · Published: 2024-11-04
- File: https://detailenjoyer.com/assets/videos/DB9YJAApIZF.mp4

### Transcript

Did you know, when copper sulfate, hydrogen chloride and aluminum are combined, a fascinating reaction can occur, producing a distinctive blue or green flame. Here's how it works. Aluminum reacts with copper sulfate, causing a redox reaction, where aluminum displaces copper, releasing copper metal and aluminum sulfate. When hydrogen chloride is present, it can intensify this reaction, especially if the solution is heated. Copper ions from the copper sulfate then release a blue-green flame when burned, because of the unique way copper's electrons are excited by heat. NOW YOU KNOW!

## Questions & answers

**Q: Which metal colors the flame?**  
A: Blue-green. _(Source: Write-up · Exhibit A (Displacement) · Wikipedia: Flame test)_

**Q: What displaces copper?**  
A: More reactive. _(Source: Write-up · Exhibit B (Acid) · Wikipedia: Flame test)_

**Q: What does the acid remove?**  
A: Exposes metal. _(Source: Write-up · Exhibit C (Color) · Wikipedia: Flame test)_

**Q: Why do flames get colors?**  
A: Emission. _(Source: Write-up · Exhibit D (Electrons) · Wikipedia: Flame test)_

**Q: What test uses flame colors?**  
A: Identifies metals. _(Source: Write-up · Exhibit E (Heat) · Wikipedia: Flame test)_

## Sources

- [Wikipedia: Flame test](https://en.wikipedia.org/wiki/Flame_test)
- [Wikipedia: Copper(II) sulfate](https://en.wikipedia.org/wiki/Copper(II)_sulfate)

## Cite this case file

Easterling, Marcus. "Blue/Green." The Detail Department (DetailEnjoyer), case file DD-361, last updated Nov 4, 2024. https://detailenjoyer.com/case/blue-green/