Sugar Crystal Challenge

Student Activity:
Dissolving Challenge

You are part of a team of engineers who has been given the challenge of exploring how the surface area of sugar changes depending upon what state it is in. Sugar is available in various crystal sizes which impacts their use or application.

Types of Sugar

Sanding Sugar: Coarse-grained sugars, such as sanding sugar are often used to add sparkles when decorating baked goods such as cookies and candies.  The "sparkle" results from light reflecting off the large sugar crystals.

Granulated Sugar: Normal granulated sugars have a grain size about 0.5 mm across and are most commonly used as table sugar for use in coffee or tea.

Caster Sugar: Caster Sugar is a finer grades result from selectively sieving granulated sugar until it is about 0.35 mm.  It is commonly used in baking.

Powdered Sugar: Powdered sugar is also known as confectioner's sugar or icing sugar and is a very finely ground form of sugar.  A grain of confectioner's sugar is about 0.060 mm, while a grain of icing sugar is about 0.024 mm.  These are used a great deal in cooking, where a sugar that dissolves quickly into a fluid is preferred.  It is used in making icings or frostings and other cake decorations. 

Regardless of the coarseness of sugar, the base sugar molecules remain the same.  

 Impact on Surface Area:
The difference in surface area in a gram of sugar is much greater in a gram of powdered sugar than in a gram of caster sugar.  And the surface area of a gram of caster sugar is greater than the surface area of a gram of granulated sugar.  

 Dissolving Challenge:
Fill two clear glasses with one cup of warm water.  At the same time, put a teaspoon of powdered or confectioners' sugar in one cup and a teaspoon of granulated sugar in the other.  Answer the following questions:

Which sugar dissolved faster?  

Why do you think this was true?  How did surface area impact which dissolved first?

 

Sugar Crystal Challenge

Student Activity:
Crystal Challenge 

 What is a Crystal?
A crystal is a solid substance in which atoms, molecules, or ions are arranged in an orderly repeating pattern extending in three spatial dimensions. The process of forming a crystalline structure from a fluid or from materials dissolved in a fluid is called crystallization. The crystal structure formed from a fluid depends on the chemistry of the fluid and the physical conditions in the surrounding area, such as what the air pressure is. Snowflakes, diamonds, and table salt are examples of crystals. Crystallography is the scientific study of crystals and crystal formation.

 What is Saturation?
Substances such as sugar can only dissolve up to a certain point in water -- then if you add more sugar it will remain in its solid form -- this point is called saturation. In this lesson, we'll dissolve two different types of sugar into hot water.  Then, as the water evaporates over time, the solution will become saturated so the sugar will attach to the string and form solid molecules of sugar that will stick to the string.  These molecules will attract more and more sugar molecules until crystals form. Over time, more water will naturally evaporate and the sugar water solution will become even more saturated so the thickness of the sugar crystals on the string will grow. Your finished string of sugar crystals will be comprised of roughly a quadrillion (1,000,000,000,000,000) molecules.

 The Challenge
As a team discuss and come to a hypothesis about the following question:  If you dissolve sugars of different coarseness (granulated, powdered, cubes) in water and then grow sugar crystals, will the resulting crystals appear the same under a microscope, or will there still be a difference in appearance based on the initial coarseness of the sugar?  Answer the questions in the box below:

Describe your answer and include at least two supporting arguments for your hypothesis.

Why?
1.

2. 

 Sugar Crystal Challenge

Student Activity:
Crystal Challenge (continued)

 Testing Stage
You have received a set of materials from your teacher, including:
•	Two clean thermal glass cups or measuring cups of at least 4 cup capacity
•	2 lengths of thin cotton string that is 1.5 times as long as the cup is tall
•	2 Pencils or sticks 
•	Weight to hang on string (washer, 
•	3 cups of granulated sugar 
•	3 cups of powdered, or confectioners' sugar 
•	2 cups very hot water (should be poured by teacher)

Observation
As a team you'll be attempting to grow sugar crystals from two different sugars - granulated and confectioner's.  Remember that granulated sugars have a grain size about 0.5 mm across while a grain of confectioner's sugar is about 0.060 mm.  Observe the granulated and confectioner's sugar under a microscope or using a digital TV or monitor scope.  Record your observations in the chart below, which you'll complete after growing crystals.

	Granulated Sugar	Confectioner's Sugar	Crystal Grown from Granulated Sugar Solution	Crystal Grown from Confectioner's Sugar Solution	
Describe what you see in words

				
Sketch what you see

					
 Sugar Crystal Challenge

Student Activity:
Crystal Challenge (continued)

Investigation/Research

1.	Mark one glass cup "granulated" and the other "confectioner's" to distinguish them during the investigation.

2.	Add 3 cups of the appropriate sugar into the marked cup.

3.	Ask an adult to pour one cup of hot water into each of the two cups. 

4.	Stir the sugar into the water until it appears perfectly clear -- this means the sugar is dissolved.  Note - an alternate approach is to heat the water to a boiling point to dissolve the sugar -- if this approach is taken, the teacher should prepare all boiled liquid sugar solutions for students. 

5.	Soak a piece of cotton string into each of the sugar solutions and place it on a plate to dry for at least ten minutes. The longer it dries, the better. With this method, there will be starter crystals on the string before being placed in the sugar solution -- this can speed up the crystal process as the starter crystals provide a place for new crystals to form.

6.	For each cup, tie the appropriate string onto the end of a pencil so that the other end of the string hangs vertically in the sugar solution.  You may wish to tie a screw or bolt to the bottom of the string to make it hang straight in the sugar solution.

7.	Check the growth over time and make note of your observations.

8.	Examine a sample of the crystals that grew from granulated sugar and from confectioner's sugar under a microscope as you did with the original sample sugars. Record observations in table provided on the previous page.

 

Sugar Crystal Challenge

Student Activity:
Crystal Challenge (continued)

 Evaluation Phase
Complete the following questions as a group:

1. Compare the crystals that grew from the granulated sugar and those that grew from the confectioner's sugar?  Be sure to be specific and include illustrations if that helps you.

2. How did your hypothesis about the crystals compare to the actual results?  Were you surprised by what you found?

3. List two uses of sugar where the sugar with the greater surface area that would have been a better choice than a courser sugar.  Why do you think this is true?

4. Suggest another use for the principle of nanotechnology. For example, engineers are testing the use of nanostructures to increase the surface area of solar panels to make them more efficient because there is greater opportunity for the sun to reach a surface.  Can you think of a similar idea?

5.  What is the most interesting aspect of nanotechnology or nanostructures you learned during this lesson?