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Year 9 Student Research Project

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Parisa McGirr

on 13 November 2014

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Transcript of Year 9 Student Research Project

Risk Assessment
1 tall cylindrical glass or container (at least 200ml)
1 marble
200ml honey
At least 50ml of extra honey (to top up)
Spoon (to retrieve marble)
Scientific tweezers
Refrigerator or cool water bath
Stove/oven and warm water bath
Mercury thermometer
30cm ruler
Marker pen (to mark surface level of honey on container)

The aim of this investigation is to discover how the temperature of a fluid affects its viscosity. This will be achieved by testing samples of honey that have been heated and cooled to differing temperatures.
The relationship between honey viscosity and temperature
In this experiment, I was able to calculate the relative viscosity of honey by measuring the speed of a sinking object, and discover how viscosity was affected by change in temperature.
The lower the temperature of a liquid, the higher its viscosity will be. The higher the temperature, the lower its viscosity will be, therefore making the liquid ‘runnier’ as it is easier for it to change its shape.
These findings supported my hypothesis as well as my conducted research, proving it to be a successful experiment.
I predict that the samples of honey with a higher temperature will prove to have a lower viscosity to those at a cooler temperature. This is from my personal experience with using honey at home and my general understanding of how heat can affect certain foods.



Mr Tsui


Google Images

By Parisa McGirr
9L Science

Viscosity is the
resistance to flow
or how easily a fluid can change shape. It can be thought of as the thickness of a fluid. Viscosity only applies to fluids (liquids and gases). I discovered in my research that
as the temperature of liquids increase, the viscosity of a liquid decreases
, as I hypothesised. However, the opposite applies for gases:
the hotter a gas is, the more viscous it becomes
. In my experiment, the resistance to flow is seen as how the honey changes its shape around the marble as it sinks.
Measuring Viscosity
In my research I discovered a couple of viscosity testing methods. The
kinematic viscosity
method measures the
speed of the fluid
passing between two sensors. The
dynamic viscosity
method measures the
speed of a spherical object as it travels through the fluid
. I used the latter method in my experiment.
Why a Marble?
It’s a sphere - sinks consistently throughout testing
It’s smooth - reduces friction
It’s denser than honey
I discovered that it was important to drop the marble in the middle of the container, because fluids move faster when away from the walls of the container, and more slowly the closer they are to the wall. Dropping the marble in the centre each time avoids change in speed.
Measuring Speed
My method required calculating the speed of an object, so I found the formula:

Measuring relative viscosity of honey...

With all other variables being controlled, the marble’s speed in the honey determines the honey’s behaviour in changing shape around the marble, and therefore a change in the viscosity of the honey. This method is quite accurate in being able to fulfil the aim of this experiment.
1. Carefully pour 200ml of honey into the cylindrical container without letting any honey touch the sides of the container. Ensure the container has enough room at the top to avoid overflow when performing the experiment. Mark the surface of the honey on the outside of the container for later reference. Using a ruler, measure the height of the container from the bottom to the surface of the honey. Record this result.

2. Insert a thermometer into the container of honey and place in the refrigerator or a cool water bath. Remove the container from the refrigerator/water bath when the thermometer reads 4°C.
3. Quickly remove the thermometer and wash and dry it completely. (NOTE: To ensure the best chance of an accurate experiment, do not wait too long between the following steps as over time the temperature of the honey will cool down or warm up to the temperature of its surroundings.)

4. Grab the marble with the tweezers (if the neck of your container does not allow you to fit your fingers) and hold the marble just above the surface of the honey, in the very centre. Have the stopwatch ready in your other hand.

5. Simultaneously drop the marble and start the stopwatch. Observe as the marble sinks.

Independent variable:
The temperature of the honey

Dependent variable:
The speed of the marble travelling through the honey (to determine viscosity)

Controlled variables:
The same amount of honey
The same type of container
The same marble

6. Stop the timer as soon as the marble touches the bottom of the container.

7. Record the temperature of the honey and the time (in seconds) for the marble to reach the bottom, on a piece of paper.

8. Retrieve the marble with a spoon, and wash and dry both completely. Top up container of honey to the 200ml marker.

9. Repeat steps 2 to 8 two more times to increase the accuracy of the experiment. Each repetition, record the results, wash and dry necessary equipment and ensure that the honey level is always at 200ml.

10. Repeat the whole experiment with honey at room temperature (22°C) and heated (40°C). Include repetitions, measure temperatures with the thermometer and use cool or warm water baths to heat and cool honey to desired temperature.

11. After the experiment, calculate the average for each temperature and create a table of all the results.

12. Calculate the average speed of the marble by dividing the height of the honey in the container by the average time for the marble to reach the bottom (speed = distance / time). Record this averaged result in a line graph and show a line of trend.

Time for marble to sink in honey
Speed of marble sinking in honey
Distance = 115mm

NOTE: All measurements have been rounded to
only 1 or 2 decimal places

In my results, I displayed two graphs: one showed the dependent variable as the time for the marble to sink (measured in seconds), and the other showed it as the speed of the marble sinking (measured in millimetres per second).
It was important to convert the times into speed, as this is a better unit for determining viscosity in any amount of liquid; unlike time, it is non-specific and relates more to determining viscosity.
For an accurate and consistent graph result that shows a trend, I decided upon my temperatures by having them in equal increments of 18°C.
(Cool temperature = 4°C, Room temperature = 22°C, Warm temperature = 40°C)
The trends in my graphs were exponential. For the time graph the hotter the temperature, the quicker the time. For the speed graph the hotter the temperature, the faster the speed.

The exponential trend line in a perfect experiment would pass through every X mark (average mark) and give a perfect trend. My results weren’t perfect but were quite accurate, with the trend line almost reaching the highest and lowest average data point.
There weren’t many limitations or problems encountered in my experiment.
The only limitation was human error when timing marble drops, especially with the 40°C honey because the marble dropped in a couple of seconds.
A slight problem was that at the start the honey had lots of trapped air bubbles which could slightly affect the total volume but also affect how the marble travels through the honey. I solved this problem by heating the honey in a warm water bath so the bubbles rose to the top, then I cooled the honey to the temperature I needed.

My experiment had no unexpected results.
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