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The science topic which I have selected is the interactions and changes of materials. This involves material change from one form to another. (For example. ice to water) The reason why I chose this topic is because students apply this scientific knowledge and understandings across to a variety of circumstances in their life (Lewis, 1991, p. 58). Students are able to determine how different substances are formed or how they can change one form of matter to another substance. For example, students will understand how water can turn into gas through steam evaporating in to the air or how they can turn water in to a solid by freezing it in a freezer.
The purpose of this assignment is to search a specific science topic to expand our knowledge based on that topic. We then review the literature to identify any other conception children might have with this topic. After reviewing the literature, we must develop a rationale of how we can address these alternative conceptions in a sequence of science lessons in the classroom.
Nothing is of more importance to a students understanding of a text than the knowledge they already have about a topic (Moss, 2003, p. 92). Prior knowledge is the foundation for future learning and provides a hook for students to hang their new learning's on to (Moss, 2003, p. 92). A student's ideas and understandings of a topic come from what they have learned previously. When a topic or concept is being taught to a group of students, the educator must consider how much prior knowledge the students have in order to plan their lesson accordingly. If an educator wishes to teach children how water can be a liquid, a gas and a solid but the students have no knowledge of the three states of matter or how the substances can change form, the students will not be able to understand the purpose of the lesson. Fleener, Morgan and Richardson (2009, p. 71) found that teachers need to both determine students' prior knowledge in teaching and build on that knowledge to frame a lesson in a proper learning context. If prior knowledge is ignored, the audience may learn something opposed to the educator's intentions. Fleener et al. (2009, p. 72) found that students may also find it difficult to formulate learning goals adequately and often have difficulty asking questions relating to the topic. For all these reason, teachers must determine the prior knowledge of their students about any relevant topic.
Science Topic and Background Content
What is matter?
Everything that surrounds you is made up of matter, including you. Anything that has mass can be defined as matter. Most of the materials and substances you would use on a daily basis, such as food, drinks, plastic, paper, are all different types of matter. The three forms of matter are solids, liquids and gases.
What is Properties?
Every substance has its own property that allows you to determine the differences from other substances. For example, Water is Transparent, Metal is hard, Trees are green. Scientist groups things based on their properties to make studying them easier. The study of matter and its properties is called chemistry. A scientist who studies matter and its properties is called a chemist. A chemist is someone who has studied matter and its properties and can make an observation. An observation is gathering information using your senses. Scientist usually records their observations so that they can compare their observations with other observations and report them to people. When we use a substance, we use it because it has properties that make it useful for whatever its purpose. Scientist have created many materials which we can use for different purposes. These materials have gradually been replaced by other materials, either to improve the purpose or to create more options for people.
States of matter
One way that can be used to group matter is its state. The three natural states of matter are: solids, liquids and gases. Matter can change its states from one form to another. For example, water can be a solid, a liquid and a gas.
Solids are everywhere around us and are very important in our daily lives. Some solids which we use on a daily basis are the bed we sleep on, the chair we sit on, the books we read, the coach we relax on and the glass we drink from. These solids include substances such as wood, plastic, glass, fabric. Some foods that we eat can also be a form of solid.
The most important liquid on earth is water. Without water, human survival would be impossible. We use water for many different purposes. Some of these are drinking, washing up, cooking, watering our garden, dissolving things and for many more purposes. Liquids that we use on a daily basis can be liquids that we might consume, during a meal, are milk, juice, soft drinks and tea. Other liquids which we might use during the day can be when taking a shower or washing dishes after a meal. Fuels, sauces, cleaning agents are all forms of liquids.
Gases are essential for our survival because the air that we breathe, to stay alive, is made up of different gases. The air that we breathe is made up of oxygen, nitrogen, carbon dioxide, and small amount of other gases.
State of matter
Solids do not change their shape even when they are moved from place to place. Solids also have a constant volume which cannot be compressed.
Liquids do not form any shape or have a constant shape, however it does have a constant volume. When a liquid is poured into a cup it will take the shape of the cup but won't have a permanent form. If the liquid is poured on a table, it will spread out and won't form any shape. Liquids cannot be compressed. Gases have no shape or constant volume. A gas can be compressed. A large amount of gas can be compressed into a small space. The diagram below will give you an idea of the states of matter of each substance.
Solutions are a special type of mixture in which the different substances such as liquid and solid spread evenly through the mixture. This is when the solids dissolve in the liquid. The individual substances are not visible in a solution because the substances spread out evenly. An example of this is salt and water. When salt and water are mixed, salt dissolves in the water. However, when sand and water is mixed together, the sand sinks to the bottom and does not spread evenly. This is not a solution.
It is important to that we are able to test the levels of chemicals in particular foods to protect our health. You can always tell a mixture because the substances in the mixture can be separated from each other in different ways. Sometimes mixtures need to be separated because some components maybe more important or useful. For example, Mining companies extract iron ore from rocks, crude oil is separated into useful components such as petrol, diesel, oil and kerosene, Indigenous Australians use dye extracted from plants and coloured minerals from rocks to produce art work and rubbish is separated into categories for recycling, composting and dumping. Each mixture is separated into their components in many ways. The method used to break up the components is based on the properties of the mixtures and its components.
Another way to group matter is to figure out whether it is a mixture or a pure substance. Most things found in nature include, water, rock, salt and air. These are mixtures of solids, liquids and gases. When we inhale air, we are breathing a mixture of gases that include oxygen, nitrogen and carbon dioxide. Many mixtures have been formed to meet a particular purpose for example paints, cosmetics sunscreen etc. everything we eat and drink is a mixture
Filtering is done all the time without us realising. For example, our nose is constantly filtering the pollen from the air we breathe. The tea that we drink is being filtered through the tea bag. Some substances that are in tea dissolve in hot water, giving your tea its flavour. The material of the tea bag acts as a filter, allowing the dissolved substances to run through the material but keeping the leaves inside the tea bag. Filters are used to remove substances that do not dissolve in liquid. (See the diagram below) Some examples of filtering are is the washing machine. The washing machine allows the water to run out of the holes in the bowl but traps the clothes inside the machine. Another example is a vacuum cleaner which sucks dust and other substances into its bag; it traps them while allowing air to pass through.
Evaporation is used when dissolved solids needs to be collected from a solution. An example of this is salt that has been collected from the sea water by evaporating the water. This can be shown through the diagram below.
Children's alternative conception on this science topic
Some alternative conceptions children have about interactions and changes of materials - are the following:
- Gases are not matter because most are invisible.
- Gases do not have mass.
- A "thick" liquid has a higher density than water.
- Particles of solids have no motion.
Children enter their classroom with their own ideas and understanding of the science topic they are about to learn. They develop these ideas and understandings by communicating with others, reading books or previous experimenting. Curriculum experiences should be designed to give young children frequent opportunity to begin exploring concepts, which provide the foundation for future learning. (Curriculum Framework, 2001). By using their prior knowledge, understanding and ideas of how things work around them, students create their conceptions of how thing's work in science. For example, if a student experiments with a 'thick' liquid passing through a beaker much slower than water, they will determine that the 'thick' liquid will have a higher density than water because it took the 'thick' liquid longer to pass through the beaker. Children can relate this to their past experiences such as make a thick milkshake and pouring it into a glass. Children use this experience and say the milkshake took longer to pour into my cup but water didn't take long as all.
When children think of gas, they sometime think of the air that surrounds us or the air that we breathe in. They will relate gas to the invisible air surrounding us. Children's conception of gas is that it is not a substance because it is not visible, and it has no mass because it is like thin air. The thought that air has no weight and we do not feel anything heavy on ourselves when we run our hands through the air, gives the conception that gas must also be the same since we cannot see it or feel it. Because individual molecules are widely separated and can move around easily in the gas state, gases can be compressed easily and they have an undefined shape. (Vision Learning, 2000)
The conception that, the particles of solids have no motion comes from, the molecules in solid that are closely bonded and tightened up to form a solid. Students start to believe that if the molecules of this substance tightens up and bonds very closely, then particles are restricted from any movement. This is not the case. The particles do have motion, but very limited. Individual molecules stay fixed in place and vibrate next to each other.
As the temperature of a solid is increased, the amount of vibration increases, but the solid retains its shape and volume because the molecules are locked in place relative to each other. (Vision Learning, 2000) An example of this is a block of ice. When ice is examined closely the crystal nature of the solid is visible. When examined even closer, the rigid lattice structure where each molecule is locked into place but move due to vibration energy. Unfortunately this cannot be shown in motion.
It is very important for teacher to address these conceptions in class to students. If a student continues to think that gas is not a matter because it is not visible, they will have trouble understanding the existence of other substances that cannot be seen, such as chemicals like oxygen, carbon dioxide, nitrogen etc. Students who may have these conceptions, and have not yet addressed them with their teachers, may live thinking that the conceptions they have are true. They won't be able to comprehend new information, on that topic, if their conception is not right. Teachers need to structure learning activates that promote interaction, so that children learn to reflect on and evaluate their own learning idea by talking with others. (Curriculum Framework, 2001)
Rationale for teaching to alternative conceptions
To address the conception of gas being present in a room position students around the room and spray deodoriser on one side of the room. It shouldn't take much time for student on the other side of the room to detect the smell of the deodoriser. Once the students have detected the smell, ask them to raise their hands. On a hot day the movement of the gas should be faster. The students can continue to play with different deodorizers to identify the different smells. Students must be careful when spraying the deodoriser and must not spray if anyone is close by. The student must spray towards the ceiling to avoid any eye contact with the chemicals. The teacher must inquire about any health issues students may have with the deodoriser or if they have asthma or breathing problems.
This sort of activity will clearly show students that gas is present around us. The movement of smell of the deodorizer was based on the temperature of the room. This also shows the students that when the temperature of any space is high, gas will move faster, if the temperature of a space is low, the movement of gas will be slow.
To address the conception of 'thick' liquid having a higher density than normal liquid. Provide students with 250 ML of liquid foam and 250 ML of water. Students must measure and weigh the two liquids with a scale. Before starting the activity, ask students which liquid they think will be heavier? It is more likely for students to choose foam because visually foam will look denser than water. The weight difference between the two liquids will be prominent to the students. This will prove their conception of thick liquid having a higher density than water to be incorrect. Students may require assistance while performing this activity as it may involve materials that can be hazardous to the students. Such as, glass or sharp objects.
To address the conception of the particles of solids having no motion, Take the students around the school and ask them to identify any cracks or fractures in brick walls or on concrete floors. Once they have identified a few of them, ask the students why they think the fractures or cracks may have appeared in the walls or on the floors. Start to explain the reason why these cracks or fractures appear. Although the brick walls and concrete floors are solids, this does not mean there is no movement within the particles. They are greatly affected by temperature around them. For example, when temperature is high they loose moisture which makes the cracks appear by slightly shrinking. There are other examples such as solid timber which are also affected by temperature and weather fluctuations. The students then should come back to class and write a list of other solids which they think might also be affected by their surroundings to form movement in their particles. When carrying out this activity, students must be aware of their surroundings, if using alternate locations such as a park, outside the school grounds etc.
These activities give students the skills to investigate further on a conception they have. It gives students the skills to be more critical of their conceptions and not accept an idea just by seeing it visually but experiment further. All three of these activities address the relevant process skills for investigating in science. They all involve investigating, making observations and asking any further questions.
- Curriculum Framework: for Kindergarten to Year 12 Education in Western Australia. (2001). Osborne Park, Western Australia: Curriculum Council
- Fleener, C., Morgan, F. R., Richardson, J. S. (2009). Reading to Learn in the Content Areas. United States of America: Cengage Learning.
- Lewis, E.L. (1991). The process of scientific knowledge acquisition of middle school students learning thermodynamics. University of California.
- Moss, B. (2003). Exploring the literature of facts. New York: The Guildford Press.
- Nasa, (2005). Retrieved April 9, 2010, from http://www.grc.nasa.gov/WWW/K-12/airplane/Images/state.gif
- Roschelle, J. (1995). Learning in Interactive Environments: Prior Knowledge and New Experience. Dartmouth: University of Massachusetts
- Spark notes, (2010). Retrieved April 9, 2010, from http://img.sparknotes.com/figures/0/07cf18f888c9c21f4b45687743b63ac3/solnform.gif
- The Outer Plantes. (2008). Retrieved April 9, 2010, from http://lasp.colorado.edu/education/outerplanets/images_spacejunk/thumbs/state_diagram.jpg
- Vision learning, (2000). Retrieved April 9, 2010, from http://www.visionlearning.com/library/module_viewer.php?mid=120