How can we Identify Acids and Bases?

The video "How can we identify acids and bases?" is an introduction to the concept of pH for young learners. The experiment utilises red cabbage as a natural pH indicator to distinguish between acidic, basic, and neutral substances commonly found at home.

This experiment should precede the two activities “How does Acid Rain Damage our Buildings?” and “How does Acid Rain Affect Plants?”.

Lilu is confronted with a challenge. He has three glasses filled with clear liquids, but the contents remain a mystery to him. The liquids in question include window cleaner, tap water, and vinegar or lemon juice. How can we help Lilu find out what the liquids are, in a safe manner?

The experiment focuses on the property of red cabbage as a natural pH indicator. When adding the solutions whose acidity we want to check to the red cabbage solution, it changes its colour. Thus, students can visually observe and classify substances based on the colour of the red cabbage solution.

By linking the experiment to the effects of acid rain, students will develop an early awareness of for environmental issues caused by human activities. Acid rain is not directly related to climate change, but is another result of burning fossil fuel.

Through hands-on experiments, students will acquire essential skills in conducting experiments, accurately recording observations – all of which are crucial for future scientific pursuits.

Instead of boiling the water to prepare the indicator solution, you can also smash the red cabbage leaves to avoid using hot water with younger children.

To prepare the indicator, you need:

• a few red cabbage leaves
• deionized water or tap water
• a mortar

The kids can make the indicator on their own, but as it gets messy, wearing gloves and aprons is highly recommended.

For instructions for creating the indicator, watch the video:

This worksheet helps children to understand how to identify an acid or a base using a natural indicator.

You can download it as docx and pdf file.

Acids and bases have different properties. Acids are substances, some of which have a sour taste, like sour candies or lemon juice. Bases are the opposite of acids. Some of them have a bitter taste or feel slippery when you touch them, like soap. ¹ Other things are not acids, nor bases. These are called neutral solutions. Water is a great example for a neutral solution. It doesn't taste sour or bitter, and it doesn't feel slippery.

But in chemistry we can't taste or touch solutions to distinguish whether they're sour or bitter, due to health and safety concerns, so we have to look for another way to find this information.

In order to test whether a substance is an acid or a base, you can dissolve it in water (if it is not already a liquid). Then you may use an acid-base indicator which changes its colour depending on whether the solution is an acid or a base. Red cabbage leaves contain a substance called anthocyanin that changes colour depending on whether they are mixed with an acid or a base. In the presence of an acid, it acquires a pink or red colour and in the presence of a base, it acquires a blue or green colour. In the presence of a neutral liquid or solution, it retains its purple colour.

The pH scale is a scale to determine how acidic or basic a substance is. The scale goes from 0 to 14, with below 7 being acidic and above 7 being basic. This scale is important in areas such as agriculture, as different species grow better in a soil with a certain pH. It is also important to measure the pH of products we use daily, like water, to ensure their quality.

Easier

• Use red cabbage to make strips of pH indicator paper. Simply soak sheets of paper in the red cabbage indicator solution, leave to dry and then use as indicator paper to test different liquids or solutions.
• Children with a greater aptitude for more artistic areas can create drawings and even organise an exhibition using their own hand-made watercolours and paper previously painted with red cabbage solution.

More challenging

• Challenge them to make predictions about the results before conducting the experiment. Ask them to explain why they think a particular substance will have a specific pH.
• Suggest that they propose additional experiments to resolve a problem, like: How can we neutralise an acidic substance?

By exploring this experimental activity, children can be inspired to consider future careers in science. This could be a good opportunity to spark interest in professions that seek to understand and find solutions to climate change, such as an environmental laboratory technician.

Environmental laboratory technician

Environmental laboratory technicians conduct water quality testing, analyse hazardous waste, and prepare samples for testing. They also calibrate and operate lab equipment, document results, and perform quality control and assurance procedures.

Environmental science and protection technician video

What is an environmental laboratory technician?
Environmental laboratory technicians are scientists who work in a laboratory to analyse samples from the environment. They analyse various samples such as water, soil, and air samples to search for pollutants and contaminants. Environmental laboratory technicians use a variety of specialized equipment and techniques to detect harmful substances. Through their work, they ensure that our environment is safe for everyone.

What does a day in the life of an environmental laboratory technician look like?
Environmental laboratory technicians can work with different samples like air, water, or soil. They measure temperatures, mix substances, put labels on samples, use microscopes to see something that is very small, and other instruments to do analyses. During their day they can analyse data using specific computer programs and can meet with other technicians to share their findings.

What responsibilities do they have?
Environmental laboratory technicians may work for government agencies, environmental consulting firms, or private laboratories. It is their responsibility to perform analyses in accordance with certain standards to ensure that the results are reliable. Through this, they enable their institutions to act to protect the environment.