The Sci Guys: Science at Home - SE2 - EP4: Red Cabbage pH Indicator - Acid Base Indicator

Summary

In this episode of Sci Guys, Ryan and Adam demonstrate how to create an acid-base indicator using red cabbage. The process involves blending cabbage leaves with warm distilled water, filtering the mixture, and testing it with various household substances like vinegar, lemon juice, baking soda, and ammonia. As each substance is added, the cabbage solution changes color, revealing the acidity or alkalinity of the solution. The experiment teaches about pH levels, how indicators work, and the role of anthocyanin in red cabbage. The video also explains the science behind color changes and the reversibility of the indicator's response.

Takeaways

• 😀 Red cabbage, also known as purple cabbage, is used to create an acid-base indicator that changes color in the presence of acids and bases.
• 😀 The materials needed for the experiment include red cabbage, vinegar, lemon juice, baking soda, ammonia, distilled water, coffee filters, and a blender.
• 😀 Safety precautions are essential, including wearing gloves, goggles, and an apron, and having adult supervision due to the use of sharp objects and hot water.
• 😀 The experiment begins by blending red cabbage leaves with warm distilled water to extract the pigment used as the indicator.
• 😀 The filtered cabbage solution is divided into several glasses, and different solutions are added to test their pH levels.
• 😀 Ammonia turns the cabbage indicator green, indicating it is a strong base.
• 😀 Baking soda mixed with distilled water creates a blue color in the indicator, indicating a weak base.
• 😀 Tap water, which is slightly basic, turns the indicator a faint blue, but mostly retains a purple hue.
• 😀 Antacid tablets produce carbon dioxide and cause the indicator to turn maroon, indicating an acidic environment, but it shifts back to purple after the fizzing stops.
• 😀 Vinegar and lemon juice both cause the indicator to turn bright red or pink, signaling they are acidic solutions.
• 😀 pH is a scale measuring acidity or basicity, with lower values indicating stronger acidity, and the cabbage indicator helps visualize these changes by reflecting different wavelengths of light.

Q & A

What is an acid-base indicator?

An acid-base indicator is a solution that changes color when exposed to an acid or base. It can change color suddenly at a specific pH or gradually through multiple colors as the pH shifts.

What materials do you need to make an acid-base indicator using red cabbage?

You will need a couple of glasses, a blender, coffee filters, a funnel, distilled water, red cabbage, baking soda, vinegar, lemon juice, ammonia, and antacid tablets.

What safety equipment should you use when conducting this experiment?

You should wear gloves, goggles, and an apron or lab coat to protect yourself from spills or splashes. Also, adult supervision is recommended since the experiment involves hot water and sharp objects.

How do you prepare the cabbage solution for the experiment?

Start by adding four cups of warm distilled water into a blender, then add two red cabbage leaves. Blend the mixture until smooth, making sure the lid is secure.

Why do you use a coffee filter and funnel in the experiment?

The coffee filter and funnel are used to filter out small pieces of cabbage, ensuring that only the liquid solution passes through for the pH testing.

What color does the cabbage solution turn when ammonia is added, and what does this indicate?

When ammonia is added, the cabbage solution turns green, which indicates that ammonia is a strong base.

What happens when you add vinegar to the cabbage solution?

Vinegar turns the cabbage solution a bright red or pink color, which indicates that vinegar is an acidic solution.

How does the pH scale relate to acidity?

The pH scale is used to measure the acidity of a solution. A lower pH indicates higher acidity, while a pH of 7 is neutral. Solutions below 7 are acidic, and those above 7 are basic (alkaline).

What causes the color change in the cabbage indicator when an acid is added?

When an acid is added to the cabbage indicator, it floods the solution with hydrogen molecules, which causes the anthocyanin molecules in the cabbage to change shape and reflect red wavelengths of light, making the solution appear red.

What is the role of anthocyanin in the red cabbage solution?

Anthocyanin is the natural pigment in red cabbage that acts as an acid-base indicator. It changes color in response to the pH of a solution, allowing us to visually detect whether a substance is acidic, neutral, or basic.