Effect of heat on the strength of hair

Topics: Sensor, Hair, Temperature Pages: 6 (651 words) Published: January 29, 2014


Effect of heat on the strength of hair
IB Biology
Phang Seow Ling

Introduction
BACKGROUND INFORMATION
A fibrous component, keratin is the main structural component of hair that intertwines and strengthens hair, retaining hair moisture and thus hair strands are likely to break. Hair tends to have an outer layer of keratin that makes it smooth, but when exposed to heat this layer is damaged, making the hair appear dry and more brittle. AIM/RESEARCH QUESTION/PROBLEM

This experiment will investigate how heat affects hair strength, by applying different amounts of heat to each strand and see how much force is needed to break it at 30 (control, standard room temperature), 50, 60, 70, 80 & 90°C. HYPOTHESIS

As temperature rises, the force required to break the hair strand decreases. Materials

Beaker (200ml)
Temperature sensor
Spirit lamp
6 almost identical hair samples
Wire gauze
Clamp stand
Data logger, dual-force range sensor
Tweezer
Lighter
Tripod stand (attach utility handle)

Variables
Type of variable
Variable
How controlled
Units, uncertainty
Description
Independent
Temperature
Measured with temperature sensor; heat source from spirit lamp ±0.001°C
This is what we control to vary the amount of heat, sensor and data logger used to minimize uncertainty Dependent
Force required to break hair
Measured with dual-force range sensor
±0.001N
This measures how brittle the hair is, sensor and data logger used to minimize uncertainty Controlled
Amount of water
Measured with 200ml beaker
±25ml
Hair strands are immersed together in the same beaker throughout the experiment

Thickness of hair strands
Visual comparison
Too small to be measured
Risk of experimental error as there’s no instrument to accurately measure hair thickness & no 2 strands will be the same

Method
1. Fill beaker with 200ml of water.
2. Put wire gauze on tripod stand and place beaker on it.
3. Suspend dual-force range sensor on clamp stand and connect it to data logger along with temperature sensor; both should be accessible with LoggerPro software. 4. Collect 6 hair samples and using tweezers, immerse them into the water. Heat beaker with lighted spirit lamp, using temperature sensor to monitor amount of heat. 5. When sensor reads 30°C, extract one strand of hair from beaker. Place it over the hook on dual-force range sensor, and apply physical force to it until it breaks. This should happen within 10 seconds. 6. Repeat the same with 50, 60, 70, 80, 90°C and collect results. Data collection

Table 1 – force required to break hair strands in different temperatures/ Newtons (N) to 3d.p. Temperature/°C
30
50
60
70
80
90
Time/s

0
0.000
0.000
0.000
0.000
0.000
0.000
1
0.000
0.000
0.000
0.000
0.000
0.000
2
0.000
0.000
0.000
0.235
0.000
0.520
3
0.917
0.214
0.214
0.887
0.673
0.979
4
1.315
0.565
1.284
1.141
1.529
0.000
5
1.765
1.051
0.000
0.000
0.021
0.000
6
2.049
1.246
1.254
0.000
0.000
0.000
7
0.000
1.504
1.457
1.652
0.000
0.000
8
0.000
0.000
0.000
0.000
0.000
0.000
9
0.000
0.000
0.000
0.000
0.000
0.000
10
0.000
0.000
0.000
0.000
0.000
0.000
Data processing
Table 2 –Average amount of force required to break hair strand in different temperatures/ N to 3d.p. Temperature/°C
Force required/ N
30
0.550
50
0.416
60
0.383
70
0.356
80
0.202
90
0.136
Data presentation – Force required to break hair strand against temperature

Conclusion
The hypothesis - as temperature rises, the force required to break the hair strand decreases is correct. At room temperature (30°C) the force required to break hair strand is 0.55N, and at 90°C it is only 0.136N. The force needed decreases steadily from 50 to 70°C but drops drastically from 70°C to 80°C. This is probably because of the increase in temperature that has damaged most of outer keratin layer, thus making the hair extremely brittle – a small amount of force is enough...
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