Investigating Colour Changes of Natural Indicators in Acids and Bases
1. Objectives
To prepare natural indicators from commonly available plant materials.
To observe colour changes in acidic and basic solutions.
To compare the effectiveness of different natural indicators.
To identify which natural indicators produce the most distinct colour changes.
2. Suggested Natural Indicators
Students should select at least five materials from the following list or can use other colorful flower or fruits.
1. Hibiscus
2. Turmeric (बेसार)
3. Red cabbage
4. Butterfly pea (अपराजिता)
5. Black grapes
6. Beetroot (चुकन्दर)
Students may also investigate other locally available coloured flowers, fruits, and leaves. Not all coloured extracts will be effective indicators.
3. Materials Required
Five or more natural materials from the suggested list
Lemon juice or vinegar (acid)
Baking soda solution (base)
Plain water
Transparent glasses or test tubes
Warm water, spoon and filter cloth
Labels and notebook
4. Experimental Procedure
Collect at least five suggested natural materials.
Crush each material separately and extract its colour using a small amount of water. For turmeric, prepare a dilute yellow mixture.
Filter the extracts where necessary.
Label three test tubes or transparent glasses as Acid, Neutral and Base for each indicator.
Add equal quantities of lemon juice, plain water and baking soda solution to the respective glasses.
Add the same quantity of natural indicator to each glass.
Observe and record the colour changes.
Repeat the experiment for every natural indicator.
5. Observation Table
Students must complete this table based on their experiments. Do not fill in the expected colours before testing.
Natural indicator | Colour in acid | Colour in plain water | Colour in base |
|---|---|---|---|
Hibiscus | |||
Turmeric | |||
Red cabbage | |||
Butterfly pea | |||
Black grapes | |||
Beetroot |
6. Questions for Analysis
Which natural indicator showed the most noticeable colour change?
Which indicators showed different colours in acidic and basic solutions?
Which natural indicator did not show a clear colour change?
How did turmeric behave differently from the other indicators?
Can all coloured plant extracts be used as acid–base indicators? Explain.
Which indicator would you recommend as an alternative to a laboratory indicator? Give reasons.
7. Conclusion
Write a short conclusion (100–150 words) explaining your experimental findings. Identify the most effective natural indicator and support your answer using the observed colour changes.
Report Format
INVESTIGATION
OF COLOUR CHANGES OF NATURAL INDICATORS IN ACIDS AND BASES
A PROJECT WORK SUBMITTED FOR PARTIAL FULFILLMENT OF REQUIREMENT IN
OPTIONAL SCIENCE CLASS 10
Submitted by:
[name of student]
Class:10
Section: …..
Roll no……
Submitted to :
[name of teacher]
Department of Science
Mount View English Boarding school
Ghorahi Dang
1. Introduction
Acids and bases are important chemical substances that
we use in our daily lives. Lemon juice and vinegar are examples of acidic
substances, whereas soap solution and baking soda solution are examples of
basic substances.
An indicator is a substance that helps us distinguish
between acids and bases by showing a change in colour.
Some natural materials obtained from plants can act as
acid–base indicators. Their colours may change when they come into contact with
acidic or basic solutions.
In this project, I investigated different natural
materials to observe their colour changes in acids and bases and compare their
effectiveness as indicators.
2. Objectives
The main objectives of this project were:
- To
prepare indicators from naturally available materials.
- To
observe their colours in acidic, neutral and basic solutions.
- To
compare the colour changes shown by different indicators.
- To
identify the most effective natural indicator among the tested materials.
3. Materials Required
The following materials were used for the experiment:
Natural materials:
- …………
- ………………..
- ……………….
- …………………
- ……………….
- ……………….
Other materials:
- Lemon
juice
- Baking
soda solution
- Dilute
soap solution
- Plain
water
- Transparent
glasses
- Spoon
- Warm
water
- Filter
cloth
5. Experimental Procedure
Step 1: Preparation of natural indicators
Some natural materials: hibiscus, turmeric, ………………………………………
were collected.
Those plant materials were crushed separately and
mixed them with a small quantity of warm water to extract their colours. The
crushed material is filtered with the help of clean cloth and collected in
different glass.
Step 2: Preparation of test solutions
Three types of solutions were prepared:
- Acidic
solution: Lemon juice diluted with water
- Neutral
comparison: Plain water
- Basic solution: Dilute soap solution / baking soda
solution (write one which you have used)
Step 3: Testing the indicators
Three clean glasses were taken for each natural
indicator and labelled them Acid, Neutral and Base.
Equal amounts of the respective solutions were poured into
the glasses.
Then an equal quantity of natural indicator were added
to each glass and carefully and colour changes was observed.
Observations was recorded in a table and results are
compared.
6. Observations
|
Natural indicator |
Acidic solution |
Plain water |
Basic solution |
|
Hibiscus |
|
|
|
|
Turmeric |
|
|
|
|
……… |
|
|
|
|
……………… |
|
|
|
|
……………… |
|
|
|
|
…………… |
|
|
|
7. Analysis and Discussion
From the sample observations, it was found that
different natural materials behaved differently in acidic and basic solutions.
Red cabbage showed
a clear difference between acidic and basic conditions. Its extract appeared …………
in the acidic solution and ………… in the basic solution.
Hibiscus also showed
noticeable colour changes. Its extract became ……… in the acidic solution and ………….
in the basic solution.
………………….(write similar to all
the indicators)
The experiment suggested that not all coloured natural
materials are equally effective as acid–base indicators.
Some plant pigments change their molecular structure
depending on the acidity or basicity of the solution. This can cause a visible
colour change.
8. Results
Based on the illustrative observations, the following
results were obtained:
- ,
…… and ……….. showed clear differences between acidic and basic solutions.
- ………………
- ………………….
- …………..
- ………………………..
appeared to be the most effective indicator among the tested materials.
9. Precautions
The following precautions were taken during the
experiment:
- Clean
and separate glasses were used for each indicator.
- Approximately
equal quantities of solutions and extracts were used to ensure
consistency.
- All
containers were labelled correctly to avoid confusion.
- Mixing
of different indicators was avoided to prevent interference with the
results.
- Chemicals
and plant extracts were not tasted during the experiment.
- Only
dilute household solutions were used, and the teacher's safety
instructions were followed.
- Colour
changes were observed against a white background to make comparisons
easier and more accurate.
10. Conclusion
In this project, six natural materials were
investigated to study their behaviour in acidic and basic solutions.
The sample results showed that red cabbage, hibiscus
and butterfly pea can act as useful natural acid–base indicators because they
produce visible colour changes under different conditions.
Turmeric was also found to be useful, particularly for
identifying sufficiently basic solutions. However, black grapes showed less
distinct colour changes, while beetroot was not very effective under the tested
conditions.
Among the materials investigated, red cabbage appeared
to be the most effective natural indicator because it produced clearly
distinguishable colours in acidic and basic solutions.
The investigation demonstrated that certain natural
plant pigments can be used to distinguish between acids and bases. It also
highlighted the importance of careful observation, systematic experimentation
and evidence-based conclusions in scientific investigations.
11. Limitations of the Experiment
- The
exact pH values of the solutions were not measured.
- The
concentrations of natural extracts were not precisely controlled.
- Some
colours were difficult to distinguish.
- The
results might change when different basic solutions are used.
- The
investigation did not determine how accurately each indicator could
measure pH.
12. References
- Class
10 Science and Technology textbook – Acids, Bases and Salts.
- Observations
recorded during the practical investigation.
- …………………
- …………….
(Students should list only the
sources they actually used.)
13. Photographic Evidence
(Here
insert the photograph taken during the experiment, it should show your face and
the materials, glasses you have used)
If
your report is hand written, print the photo and attach here.