Impact_of_Different_Cooling_Rates_on_the_Growth_of_Crystals
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Impact of Different Cooling Rates on the Growth of Crystals
Sources
Title: Science for kids: Crystals
Website: https://www.ducksters.com/science/crystals.php
Date accessed: 11/8/21
Summary: Crystals form when liquids such as magma cool extremely slowly and solidify. During this procedure it is possible for crystals to form, this process is known as crystallization. When water evaporates from a mixture, it also forms crystals. For example, salt crystals usually form when saltwater evaporates.
Title: How Do Gemstones Form?
Website:https://www.gemrockauctions.com/learn/technical-information-on-gemstones/how-do-
gemstones-form
Date accessed: 11/8/21
Summary: Gemstones can form in four ways, igneous, metamorphic, sedimentary and hydrothermal. Whilst Igneous gemstones form when magma cools and hardens, hydrothermal gems form when rich bodies of mineral water cool. Metamorphic gemstones form when they are morphed due to exposure to extreme pressure and heat and sedimentary gems form when water deposits sediments. Temperature, time, space, pressure and ingredients are the 5 requirements for forming crystals.
Title: How Does Temp Affect the Growth Rate of Crystals?
Websites: https://sciencing.com/temp-affect-growth-rate-crystals-6318908.html
Date accessed 11/8/21
Summary: There are four significant factors that affect the growth of crystals, this includes pressure, temperature,
the quantity of dissolved material and evaporation. If there is more dissolved material within the water
and a large amount of pressure is set on that material, the crystal will grow larger. The rate of the water evaporating from the solution determines the size of the crystal. If the water evaporates from the
solution slowly, few crystals form but have time to grow larger before all the water is evaporated. If the water evaporates quickly, many crystals form but don’t have time to grow as large as possible.
Aim
To test whether different rates of cooling affect the size and qualities of crystals.
Variables
Independent variable
What will be changed?
How will this be changed?
There is one independent variable (IV) known as the rates of cooling. This IV consists of three cooling rates.
For each level of IV, the temperature will differ
Level 1: 25
°
C
Level 2: 14.5
°C
level 3: 25
°C
Dependent Variable
What will be measured?
How will this be measured?
There are two dependent variables (DV) known as size (length and weight) and qualities (lustre, shape and colour)
Each of the weights of the crystals will be measured using a weighing scale. The length of the crystals will be measured using a 30cm wooden ruler and the qualities will be measured using naked eye observation.
Control variable
What needs to be kept the same
throughout the experiment?
How will this be kept constant?
Salt
Table salt will be used for each salt crystal
Temperature of water
The temperature of the water will be 120
°C
for each salt crystal
Amount of salt
794g of salt will be used throughout the experiment (86g per cup and 20g to dip the skewers in)
Amount of water
1.593L (177ml per cup) of water will be used throughout the experiment
Time of crystal growth
Each of the crystals will be given 15 days to grow
Environment/temperature for each crystal
The crystals will not be moved from their set environment/temp
Weighing scale
The same weighing scale will be used to weigh each of the weights of the crystals
Peg
The same type of peg will be used for each salt crystal
30cm wooden ruler
The same 30cm wooden ruler will be used to measure each of the lengths of the crystals
Hypothesis
The first hypothesis is that if the rate of cooling is low for a long period of time, then the length and weight of the crystals will increase. The second hypothesis is that qualities of lustre, shape and colour will not differ among the rates of cooling. Scientific Reasoning
The hypothesis in this experiment was based on research. It has been scientifically proven that if magma/lava cools slowly, it has enough time to grow larger and consequently weigh more. In contrast, if magma/lava cools quickly, it is possible for no or very small crystals to form (SCIENCING, 2018). In regards to the qualities of crystals, studies have shown that all salt crystals have the same properties despite their cooling rate and size (Exploration of Everyday Chemical Compounds).
Introduction
Crystals and gemstones are very similar but they do vary. Gemstones are expensive rare minerals that are found beneath the Earth’s surface. Crystals are pure substances whose molecules and atoms are fixed in a geometrical pattern. A gemstone can be classified as a crystal however, a crystal cannot be identified as a gemstone (Difference Between.Net, 2010). The elements and impurities within a crystal and gemstone determine the colour. For example, quartz is a colourless crystal composed of silica (Si) and oxygen (O) but when Iron (Fe) is added, the colour changes to yellow or purple (Causes
Of Colour, 2021). Many crystals and gemstones are colourless when in their pure form (Exploration of Everyday Chemical Compound, 2014). They have a lustre when exposed to light (Starting Reactions That Last a Lifetime, 2020). Crystals are made up of atoms from the same or different types
of elements (Let’s Talk Science, 2019). For example, quartz is made up of atoms from oxygen (O) and silicon (Si). Salt crystals all have the same properties regardless of their cooling rate and size (Explorations of Everyday Chemical Compound).
Crystals form due to a process called crystallization. When magma or lava cools and solidifies, crystals can grow (DUCKSTERS). Crystals form at different rates of speed, the amount of time given determines how large the crystal is (UCSB ScienceLine, 2016). If the magma cools at a slower rate, the crystals will have more time to grow. Larger crystals located in the mantle cool slowly and grow larger than those formed in igneous rocks because of the extreme heat. Igneous rocks form when lava cools and solidifies. Due to the lava cooling extremely quickly, it is possible for no or very small crystals to form.
Four significant factors affect the growth of crystals, this includes pressure, temperature, the quantity of dissolved material and evaporation. These factors can help increase or decrease the size of the crystals. If crystals cool down slowly, it has enough time to grow large, however, if crystals cool down quickly, it is difficult to form and cannot grow as large as possible (SCIENCING, 2018). The aim of this experiment was to test whether different rates of cooling affects the size and qualities of crystals. In this experiment, it was hypothesized that if the rate of cooling was low for a long period of
time, then the crystals will grow larger. It was also hypothesised that the qualities of lustre, shape and colour will not differ among the rates of cooling. This prediction was made from the research analysed for this study.
Equipment
Material
Quantity
250ml glass cup
9
Wooden skewer
9
Peg
9
Boiling water
1.593L
Table salt
794g
Metal tablespoon
1
Plate
1
2L Pot
1
Wooden ruler
1
Weighing scale
1
Risk assessment
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Risk
Precaution
Treatment
Assessmen
t
Boiling water spills
Wear gloves, lab coat and goggles. Ask an adult to assist you when handling boiling water
Do NOT touch and ask an adult to clean up any boiling water spills
Moderate
Salt in eyes
Wear goggles or glasses
IMMEDIATELY rinse eyes with cold water until the irritation disappears
moderate
Broken glass
Wear closed clothing such as closed shoes
Do NOT touch, stay back and ask an adult for help
moderate
Burns from handling boiling water
Wear protective clothing/gear such as gloves
IMMEDIATELY immerse the burn in water and cover it
with a non-stick bandage
moderate
Gas explosions
Do not leave any flammable object near the gas
Stay back and do NOT touch. Ask an adult for help
moderate
Respiratory irritation
Wear a mask
IMMEDIATELY seek medical attention from an adult
low
Burnt hair
Tie your hair back
Stay calm and expose your hair under running water
moderate
Injuries caused by the skewer
Handle with care and caution whilst being aware of the pointy end
IMMEDIATELY seek medical attention from an adult if severe
low
Swallowing/drinking the salt solution
Do not taste the solution or
leave it next to drinkable water.
Drink fresh cold water
low
Skin irritation
Wear protective gear and modest clothes that cover your skin
IMMEDIATELY seek medical attention from an adult
low
Salt entering open wounds
Cover open wounds with bandages or band-aids.
Rinse wound with cold water
and apply bandage/band aid
moderate
Method
Step 1) 1.593L of water was boiled to 120
°C in a 2L pot. Safety clothing was worn, and an adult handled the boiling water.
Step 2) 258g of table salt was poured into the boiled water and stirred with a metal tablespoon. This process was repeated three times. Prior to handling the salt, it was ensured that no open wounds were exposed.
Step 3) 177ml (¾ of a cup) of the solution was poured into each of the nine 250ml glass cups. An adult handled pouring the solution into cups as it was still hot
Step 4) 20g of table salt was poured onto a plate. Step 5) 1 wooden skewer was dipped in water and coated in the table salt, this was repeated 9 times. The skewers were handled with care to avoid the pointy side.
Step 6) 20 minutes was given for each skewer to dry.
Step 7) One salt coated skewer was placed in the middle of each glass cup and secured with a peg; this was repeated nine times. It was made sure that the skewers did not encounter the sides or bottom of the cups (see Figure 1). Step 8) Three cups were placed in the fridge (4
° C), three cups were placed in the living room (25
°C) and three cups were placed in a warm room (35
° C
caused by the heater).
Step 9) Fifteen days were given for each salt crystal to grow. The skewers were adjusted if they encountered the sides or bottom of the cups.
Step 10) The skewers were removed from each cup after 15 days.
Step 11) The crystals for each condition were measured with a 30cm ruler for length and weighed using a weighing scale. The average weight and length of the crystal for each cooling rate was calculated and the qualities were recorded.
Results
Figure 1
Diagram of Crystal Setup
Note
. Crystal solution setup is the same for each condition.
Figure Outline: The diagram above shows the setup for each cooling condition. A peg, 250ml cup, skewer and solution was used.
Table 1
Weight of Crystals for Each Cooling Rate Condition
Cooling rate
Weight of
crystal (g)
Average
weight
4
°
C
4.43g
Crystal 1
4.6g
Crystal 2
4.4g
Crystal 3
4.3g
25
°
C
3.33g
Crystal 1
3.5g
Crystal 2
3.3g
Crystal 3
3.2g
35
°
C
2.23
Crystal 1
2.4g
Crystal 2
2.2g
Crystal 3
2.1g
Note. ‘
Average weight’ for each crystal in their respective condition
Figure 1
Average Weight of Crystals for Each Cooling Rate
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Figure outline: The figure above shows the average weight of crystals for each cooling rate. The highest cooling rate had an average weight of 2.23g, the middle cooling rate had an average weight of 3.33g and the lowest cooling rate had an average weight of 4.43g. The highest cooling rate had the lowest average weight, whilst the lowest cooling rate had the highest average weight. The average weight of the crystal increases as the cooling rate decreases.
Table 2
Length of Crystals for Each Cooling Rate Condition
Cooling Rate
Length of Crystal
Average Length
4
°
C
5.4cm
Crystal 1
5.6cm
Crystal 2
5.4cm
Crystal 3
5.2cm
25
°
C
3.26cm
Crystal 1
3.5cm
Crystal 2
3.2cm
Crystal 3
3.1cm
35
°
C
Crystal 1
1.5cm
1.33cm
Crystal 2
1.4cm
Crystal 3
1.1cm
Figure 2
Average Length of Crystals for Each Cooling Rate
Figure outline: The figure above shows the average length of crystals for each cooling rate. The highest cooling rate had an average length of 1.33cm, the middle cooling rate had an average length of
3.26cm and the lowest cooling rate had an average length of 5.4cm. The highest cooling rate had the lowest average length, whilst the lowest cooling rate had the highest average length. The average length of the crystal increases as the cooling rate decreases.
Table 3
Qualities of Crystals for Each Cooling Rate
Cooling rate
Lustrous
Colour
Shape
4
°C
Crystal 1
Yes
Colourless
Geometrical
Crystal 2
Yes
Colourless
Geometrical
Crystal 3
Yes
Colourless
Geometrical
25
°C
Crystal 1
Yes
Colourless
Geometrical
Crystal 2
Yes
Colourless
Geometrical
Crystal 3
Yes
Colourless
Geometrical
35
°C
Crystal 1
Yes
Colourless
Geometrical
Crystal 2
Yes
Colourless
Geometrical
Crystal 3
Yes
Colourless
Geometrical
Discussion
The aim of this investigation was to test whether the rate of cooling affects the size and qualities of crystals. The first hypothesis was that if the rate of cooling was low for a long period of time, then the length and weigh of the crystals will increase. The second hypothesis was that the qualities of lustre, shape and colour will not differ among the rates of cooling. The results obtained in this study shows that these hypotheses were correct.
As shown in Table 1 and Figure 1, the weight of the crystals increased as the cooling rate decreased. This was because crystals cool and grow at different rates of speed and temperatures (SCIENCING, 2018). When crystals cool down slowly, it has enough time to grow large, hence weighing more. If crystals cool down quickly it doesn’t have enough time to grow as large as possible, resulting in forming no or very small crystals (SCIENCING, 2018). The temperature a crystal was set to grow in determines the rate of cooling. Cool areas will take slower for a crystal to cool and grow large, whereas warmer areas will take quicker for a crystal to cool but not grow as large (UCSB ScienceLine, 2016). For example, an area that is extremely warm, such as the mantle would form larger crystals than an area that is cooler such as the Earth’s surface.
As indicated in Table 2 and Figure 2, crystals with a low cooling rate were larger in length than those with a high cooling rate. Like weight, the length of the crystals depended on the rate of cooling and temperature. The slower crystals form, special larger, however, if the crystals form quicker they will be smaller (SCIENCING, 2018). The temperature a crystal was exposed to affects the rate of cooling.
Cooler temperatures will take slower for a crystal to grow and will be larger in size, whereas warmer temperatures will take quicker for crystals to form but will be smaller (UCSB ScienceLine, 2016). In this experiment, the temperature and rate of cooling affected the overall size of the crystals.
As shown in Table 3, the qualities of the crystals in each cooling rate condition do not differ. The results were the same for each crystal as the three cooling rates did not affect the qualities. The shape, lustre and colour of the crystals remain the same as the cooling rate decreases. This was because crystals are pure substances whose molecules and atoms are fixed in a geometrical pattern, resulting in a 3D geometrical shape (Difference Between.Net, 2010). Elements and impurities within a crystal determine the colour (Causes Of Colour, 2021). Most pure crystals are colourless (Exploration of Everyday Chemical Compound, 2014). Since salt crystals are composed of sodium and chloride, it is a pure mineral resulting in colourlessness. The crystals in each cooling rate had a lustre as it is a quality of all crystals (Starting Reactions That Last a Lifetime, 2020). Salt crystals all have the same properties regardless of their size (Exploration of Everyday Chemical Compound).
This experiment was reliable because three crystals were grown for each rate of cooling. The crystals were each measured using the same method and equipment, this secured the reliability of measuring the DV’s. This study also showed good validity as the three crystals for each cooling rate were measured three times and averaged to ensure the results were accurate. For example, the length of the three crystals for the lowest cooling rate was measured using a 30cm wooden ruler and the weight was
measured using a weighing scale. These results were then recorded and averaged.
There were errors and difficulties encountered in this experiment. One error that occurred during this investigation was that too much salt was added to the water. The water was not able to dissolve all the
salt so another batch was made. For future reference, this could be improved by researching how much salt could be dissolved into a certain amount of water beforehand. Throughout this investigation, it was difficult to keep the temperature where the crystals were growing in constant. The room temperature (25
°
C) was constantly changing, this was because the weather outside rose and
fell. A solution for this difficulty would be to place the crystals in a condition where the temperature is constant.
To conclude, it is important for society to understand what the Earth consists of. Having the knowledge of how rocks, minerals and gemstones are formed increases one’s understanding of the environment. This can be useful for society, knowing what Earth is composed of.
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References
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