We use cookies to give you the best experience possible. By continuing we’ll assume you’re on board with our cookie policy

To Identify Bio Chemicals in an Unknown Substance Essay Sample

  • Pages: 2
  • Word count: 481
  • Rewriting Possibility: 99% (excellent)
  • Category: experiment

Get Full Essay

Get access to this section to get all help you need with your essay and educational issues.

Get Access

Introduction of TOPIC

The object of the experiment is to test a substance and identify the bio chemicals, which exist in that substance.

Food tests are used to identify which bio chemicals exist in a substance. The substances characterised are in the tests are:

carbohydrates, starch, lipids and peptide bonds.


The following tests were used to identify the relevant substances:

Benedicts Test

Carbohydrates – reducing sugars such as glucose fructose and maltose

* Add 2cm3 of a solution to a test tube.

* Add an equal volume of Benedicts solution.

* Shake and bring gently to the boil, shaking continuously to minimise spitting.

Red brown precipitate result indicates reducing sugars present

Disaccharide hydrolysis test and Benedicts test

Carbohydrates – non-reducing sugars such as sucrose

* Add 2cm3 of solution to a test tube .

* Add 1cm3 dilute hydrochloric acid.

* Boil for one minute.

* Carefully neutralise with sodium hydrogen carbonate

* Carry out Benedicts test

Brick red precipitate indicates reducing sugars present, if above test is negative

Heavier precipitate indicates reducing sugars present. if above test is positive


ch Test Starch * Add 2cm3 1% solution to a test tube * Add a few drops of I2/KI

Sorry, but full essay samples are available only for registered users

Choose a Membership Plan

A blue-black colouration indicates starch present

To Identify Bio chemicals in an unknown substance


Lipids Test

Lipids such as oils, fats and waxes.

* Add 2cm3 of absolute ethanol to a test tube

* Add 2cm3 of solution to the test tube

* Dissolve the solution by shaking vigorously

* Add an equal volume of cold water

A cloudy white suspension indicates lipids are present

Biuret Test

Add 2cm3 of solution to a test tube

Add an equal volume of 5% potassium hydroxide solution and mix

Add 2 drops of 1% copper sulphate solution and mix

A mauve or purple colour indicates peptide bonds are present


Benedicts test

An unknown substance was tested and the test results were as follows:

Benedicts test – reducing sugars

As the solution was heated the substance changed from a brown to a light orange solution indicating a positive test.

Disaccharide hydrolysis test and Benedicts test

After boiling the litmus paper was dipped into the solution to check the Ph. The Ph turned red indicating a Ph of 1. Sufficient sodium hydroxide was added until the litmus paper turned olive green indicating a neutralised solution.

The Benedict’s test was carried out on the neutralised solution. The solution turned orangey red after heating, indicating a positive result.

Starch test

After the I2/KI solution was added there was no change to the substance it did not have a blue-black colouration indicating a negative result.

To Identify Bio chemicals in an unknown substance


Lipid test

After dissolving the solution in ethanol a cloudy white suspension did not form, indicating a negative result.

Biuret test

After adding potassium hydroxide and copper sulphate no colour developed indicating a negative result.


The unknown substance is a protein containing both reducing and non-reducing sugars.

We can write a custom essay on

To Identify Bio Chemicals in an Unknown Substance ...
According to Your Specific Requirements.

Order an essay

You May Also Find These Documents Helpful

Designing an Osmotic Potential Experiment with Potatoes

Osmosis is used throughout the kitchen in various countries. In France, aubergines and cucumbers are often soaked in salt to create a nicer texture, however chefs lack understanding of why this happens, as they would have forgotten about it after they finished school, they only know that it happens. Therefore, this experiment is designed to explain to the millions of chefs around the world why the water is “sucked” out of a vegetable when it is dipped into a salt or sugar solutions. I believe that having knowledge over the reason for something can open up new ways of thinking; this is why I think it is so important to explain the reason behind this phenomenon. Famous chefs are also known to be under time pressure; for example, every cooking show on TV includes some sort of time pressure scenario, weather it is a ticking clock or waiting customers. For...

Investigating the Effects of Salt on Seed...

PROBLEM/RESEARCH QUESTION In this investigation, we are researching and investigating whether the concentration/percentage of NaCl (salt) in water affects the germination rate of seeds and if so, which concentration germinates the most seeds. We will formulate our research by conducting an experiment in which we will observe the germination of seeds in various concentrations of salt water and evaluate the results gathered. In particular, we will measure the percentage of seeds germinated in one week and formulate our conclusions from there. HYPOTHESIS I hypothesise that the highest percentage of seeds will germinate in the petri dish that contains the lowest percentage of NaCl in water- 0.5% salt salinity and the percentage will decrease as the percentage of salt in the solution increases. I predict this because I know from prior knowledge that seeds need to be able to absorb H2O to germinate and salt prevents this. So if we increase...

Investigating the Effect of Sodium Fluoride on...

Graph Showing the effect different volumes of Sodium Fluoride has on the average rate of production of H+ ions as measured by the colour change of resazurine Comment on Graph: The graph depicts a positive trend, as the amount of Sodium Fluoride increases the average rate of H+ ions as measured by the colour change of resazurine also increases. This increase is consistent with each 5 mL increase of Sodium Fluoride resulting in an increase of one assigned numerical colour. This steady increase plateaus at 15mL with no further colour change. Conclusion and Evaluation Conclusion In our experiment we tested whether changing the amount of Sodium Fluoride effects the rate of respiration as measured by the colour change of resazurine. Our experiment indicates that there is a relationship between sodium fluoride and the rate of respiration. In our experiment the more sodium fluoride that was added the less colour change,...

Popular Essays


Emma Taylor


Hi there!
Would you like to get such a paper?
How about getting a customized one?