Title: To critically examine how color as well as other characteristics affect the strength of hair amongst girls.
Background Information
For a normal and healthy individual, hair fiber is strong with a tensile strength of around 1.6 x10-9 N / m2. The question then is to find out the reason why hair breaks yet it is so strong.
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"International Baccalaureate: Hair Lab Report".
Human hair is composed of a protein called keratin, water and dead cells. Each succesive strand of hair is comprised of three layers; the Cuticle, Medulla and Cortex. Cuticle is made up of scale-like, overlapping protein cells which protect the cortex. For a healthy hair the cuticle lies flat around the hair shaft while a damaged hair the cuticle of the hair is raised.
Keratin is a polyamide molecule which has many disulfide bridges in between the chains that gives the hair its strength. The hair color is as a result of eumelanin or pheomelanin. A grey hair lacks a coloring pigment. The strength of hair usually depend on the extent of the intermolecular bonds, the more the intermolecular bonds the stiffer the hair. As the linear sequence of the amino acids increases,, the strength of the hair is also enhanced.
Measuring the strength of hair at different weights and then translating the results on a graph gives a precise depiction. Also, recording the amount of weight taken to break the hair will determine the strength of hair.
To make this happen, hair strands is cut from people who do not chemically treat their hair and some strands from those who bleach, perms, or colors their hair permanently. This forms a basis in which hair strength can be measured and ascertained.
Research question: What force is required to break down a hair? How does hair color consequently affect its strength and weaknesses?
Hypothesis: Hair resistance and strength is based on the weight that is inflicted on the hair strands. Use of chemicals as well as dye and multifold colors consequently affect the strength of hair.
Variables
| Controlled Variables | Independent variables | Dependent Variables |
| Number of strands of hair used per trial | The different colors of hair | Number of breaks on the different parts of each strand of hair |
| Different length of hair used for all empirical trials | The tensile strength of each strand of hair using the force meter and clamp |
Materials:
1. 12 hairs (of different colors from) 3 per person
2. Ruler
3. Weights (100g)
4. Clamp stand
5. Force meter
Procedure:
1. Cut three hairs from four different girls
2. Measure each hair and record the measurements.
3. Choose a hair, and tight it to the force meter apparatus. You should already have the first weight (100g) hanging from this apparatus.
4. Be aware that the hair is correctly tightened up, if it does, start adding more weight after 60 seconds while observing the changes. First; the cylinder weighing 100 g and afterwards the 10g weights is added sequentially to the clamp stand.
5. When the hair breaks, record the amount of weight that it was put.
6. Repeat steps 3, 4 and 5 with all of the other hairs.
Results:
| Name | Color and Type | Length (cm) | Weight (N) |
| hair nº 1 | Blond-straight | 50 | 130 |
| hair nº 2 | Blond -straight | 40 | 130 |
| hair nº 3 | Blond-straight | 44 | 120 |
| hair nº 1 | Ginger-curly | 59 | 220 |
| hair nº 2 | Ginger-curly | 44 | 220 |
| hair nº 3 | Ginger-curly | 60 | 150 |
| hair nº 1 | Brunette-straight | 76 | 140 |
| hair nº 2 | Brunette-straight | 75 | 190 |
| hair nº 3 | Brunette-straight | 76 | 200 |
| hair nº 1 | Brunette-wavy | 50 | 100 |
| hair nº 2 | Brunette-wavy | 50 | 150 |
| hair nº 3 | Brunette-wavy | 50 | 100 |
Conclusion
The aim of this lab was to investigate the strength of hair and characteristics of different hairs that are responsible for the strength of hair. The steps mentioned in the procedure were carried out to meet the aim. In this lab, independent variable was the different hair colors and the dependant variable is the strength of the hair.
From the results, it is clear that, strong colors such as ginger and brunette add strength in the hairs. On the other hand, the blond color showed the least resistance. Although brunette hair was strong, the two types of hair used alongside this color have one difference between them. One hair strand was tested with chemicals while the other one was not. It appeared that the untreated hair was stronger than the treated hair strand. From this comparison, it shows that hair characteristics change in the inception of chemicals.
Some reasons can explain why some hairs strands are more resistant than the others. An important reason to note is that the cysteine (an amino acid that is used to break bonds notably, disulfide within the hair) bonds are too weak hence could resist much weight added. Another reason is the lack of keratin. Keratin is a fibrous protein (one with elongated shape). It is important to note that these fibrous protein lack structural elements. This fibrous protein is linked alongside cysteine by covalent bonds so that disulphide bonds are formed. When numerous disulphide bonds are produced, the fibrous protein will be stronger.
My hypothesis inferred that, some hairs are more resistance and will resist more weight. Chemically treated hairs are weaker as compared to hairs that are not treated hence break with less weight. The hair color as a characteristic also determines the strength of these hairs. From the lab results, my hypothesis is supported. However, the experiment gave more clear and proved results in terms of colors in that, certain colors give more strength to the hair strand than other colors. Although the lab experiment was done correctly certain improvements would reduce errors in results. For instance, by dividing treated hairs with non treated hairs.
