physical properties of materials

An interesting video on a new type of 'concrete canvas' with varying properties. What do you think causes one paper to be stronger than another? Learners may also remember that metals are ductile. Learner-dependent answer: some plastics, rubber, some metals (especially in thin sheets) are all examples that learners could mention. Which of the above properties would be important if you were choosing a material to make a barbed wire fence? The thermometer usually contains some type of brightly coloured liquid. It is denoted by ‘L’. Water is a liquid at 25°C. It links to what learners will do in Gr 8 Matter and Materials. We say it makes the answer more reliable. It is represented as the ratio of mass with volume of a material. Which of the above properties would be important if you were choosing a material for making cookware (cooking pots)? Shape memory 1. The temperature at which water boils is called the boiling point of water. What do you think will happen when the mixture reaches a temperature of 78°C? Sometimes, adding substances (such as ethanol) to water can bring the boiling point down (refer to Raoult's Law). It is not important that learners remember these temperatures, as they will be determining them experimentally shortly. Some points to guide the class discussion: The strength of paper is important because we use paper for many different things. 3. Why do you think plastics can be 'melted and moulded' with ease? Density of a material or substance is defined as “the mass per unit volume”. What needs to happen to water to make it boil? The thermometer is made of very thin glass. a physical property that does not depend on the amount of the material. Strength, flexibility (the ability to flex or bend), electrical conductivity and heat conductivity are important properties of materials that we learnt about in Gr. Possible answers are the metal of cooking pots conducts heat well to cook food and boil water, the metals that make up some heaters also need to conduct heat well. Ice melts at 0°C. Say. Information for students K-6 about the properties of various materials, metals, plastic and of wool, cotton and silk. Why do you say so? They cannot be compressed. The rock can contain toxic chemicals (such as cyanide) which seep into the ground and contaminate soil and water. Now draw a graph of your experimental data. When the temperature gets to a certain point (called its melting point), the wax starts to melt as it changes state from a solid to a liquid. Take a measurement of the water temperature before you start heating the water. Not all substances melt at 0°C either. Record the temperature in the table provided. Most plastics melt easily because they melt at relatively low temperatures. Probably not! In the next activity we are going to explore the boiling and melting points of a few substances other than water. The learners should note that someone placed the plastic kettle on the stove. Evaporation can take place below the boiling point of a liquid, but boiling takes place only once the liquid is heated and reaches its boiling point. The mixture is at room temperature to begin with. The point of this would be to show that the boiling point of water is constant (at constant pressure, of course, so it would make sense to do the extensions concurrently with the prescribed procedure below). We will soon find out! We learnt in Gr. Some of these typical properties of a material are listed below-. What was the temperature of the unknown liquid at the start of the experiment? Although this is hugely beneficial for the economy, it has devastating effects on the environment. Durability 4. Learn about the properties of materials as you experiment with a variety of objects in this great science activity for kids. Only then will the temperature of the water (that was ice before it melted) rise above 0°C. (Supervisory Control and Data Acquisition), Programmable Logic Controllers (PLCs): Basics, Types & Applications, Diode: Definition, Symbol, and Types of Diodes, Thermistor: Definition, Uses & How They Work, Half Wave Rectifier Circuit Diagram & Working Principle, Lenz’s Law of Electromagnetic Induction: Definition & Formula. The two words, heat and temperature, are connected but they do not mean the same thing: Adding heat energy usually results in a temperature rise, so people often confuse heat and temperature. Hang the yoghurt tub from the paper clip and hold it in your hand. Learners could be reminded that the dependent variable is the one that was 'measured' or observed; in this case the temperature of the water as it increased with time. Why did you repeat the experiment for the same type of paper? What impact do you think this has on this area? Cars have crumple zones to increase safety. Q is the amount of heat given to material in Joule. When writing a conclusion, you must go back to look at your initial aim. There are two main types of physical properties: extensive and intensive properties. Would it perhaps be safer in the event of an accident? However, this is a good extension exercise to get learners thinking about how a thermometer works and introduce the idea that materials expand (when heated) and contract (when cooled) due to the increase in kinetic energy of the particles (the size and number of the particles do not change, it is only the spaces between the particles that get bigger or smaller). A practical advantage is that gold doesn't rust. All Siyavula textbook content made available on this site is released under the terms of a Let's make some predictions. Repeat steps 1 - 5 using the other end of the strip and count the marbles again. The boiling point of ethanol is 78°C. State whether each of the following statements is TRUE or FALSE. Can you imagine your world without paper? As you can see in the previous diagram, a liquid can change into a gas by evaporation. When the person tried to heat the water, the kettle melted as a result of contact with the flame/heat. The common glass thermometer that you see in the image is called a bulb thermometer. Do you think plastic is a good choice of material for making a whole cooking pot? The investigation in the learners books includes only that of investigating boiling point of water, as suggested in CAPS. When an electric current is passed through it, it increases in size (up to a 4% change in volume). Your teacher will demonstrate how to handle the Bunsen burner safely. Set up your apparatus as shown in the image. Good conductors of heat can be used for making pots and pans, heating elements, etc. At what temperature does water boil? In order to boil water, we need to add energy to it. In order to melt ice, we need to add energy to it to raise the temperature to melting point. Let's now investigate boiling and melting. If the holes were punched at different distances from the edge, this might make some papers appear stronger or weaker than they actually are. FALSE: Two alternative TRUE statements are possible: A scientist wants to determine the boiling point of an unknown liquid. Then the Density of material. Note: Learners' graphs should have the following general shape and features: Beware that temperatures below 0°C may be recorded, so learners' graphs may not be identical. Leave the thermometer in the ice for a few minutes. What are your feelings about the golden car in the picture? Heat capacity 2. Encourage learners to write what they think of the golden car, what their thoughts and feelings are. What effects do you think this has had on the environment? When ice is heated, its temperature will remain constant until all the ice has melted. Be careful not to drop it or bump it against the bottom or sides of the beaker. It is the property of a material by which it regains its original dimensions on removal of load or force. Do you know what those are? You need to control all other variables so that the only thing you are changing is the type of paper. Allow learners to discuss how to test how strong a material is for a few minutes and come up with a few ideas. What impact do you think this has on the environment? Punch a hole at both ends of each paper strip. Unit of αA is per oC. As can be seen, these slag piles do not have anything growing on them as they are not green, and they have been there for decades, so they are reducing the possibilities for habitats and natural vegetation to grow back. (Ductile describes a material which can be drawn out into a wire.). 5 that the properties of a material determine what it can be used for. Water runoff can also contaminate water supplies. The bigger flame gives more energy to the water but does not affect the boiling point. Unit of αA is per oC. Spalling resistance 11. Measure the temperature of the water at regular intervals. Learners should be encouraged at this stage to start thinking about scientific processes and products in terms of their advantages and disadvantages. Most plastics can easily be melted and moulded into different shapes for different purposes. These properties determine how these different materials are used. If you want to create a circuit for a bulb, the material that you use in the circuit to connect the battery to the bulb must have a high ________. Do you think the time required for the water to boil would be longer, shorter or the same? Learners may say the paper that is most difficult to tear would be the strongest. 5 and have revised again here. It looks as if something has gone wrong here! The bigger flame gives more energy to the water per time unit. A material that conducts heat well is said to have a high ________. Although paper is important in our lives today, the production has negative impacts on the environment. What do you think will happen to the liquid level in the thermometer when it is put into the refrigerator? Complete the following table by adding the names of different materials that have the properties listed. It unit is mho/meter. Porosity 3. Water boils at a temperature of 100°C when the air pressure equals 1 atmosphere. The liquid level will drop. The ways we use materials and the processes we use to produce them always have an impact on the environment. Possible hypotheses are: 'The thicker and stronger the paper, the more marbles it can hold before breaking. A material that conducts heat well is said to have a high heat conductivity. This is the second part of the investigation if you would like to look at melting point of ice. Nitrogen would be a gas at room temperature, because room temperature is higher than the boiling point of nitrogen. They reduce the biodiversity in the area. The boiling point of a material is the ________ at which the liquid state of that material turns into a gas. They have not yet encountered force as a concept (force is covered in Gr 9 Energy and Change) but you could encourage them to think about what they are doing when they hang the heavy marbles on the strip of paper. Learners could be encouraged to imagine carrying a shopping bag filled with heavy items, that would simply fall through a shopping bag that is too weak or thin. We used paper strips of the same length and width. Paper mills use huge amounts of water, and the waste water contains many chemicals and substances which damage the environment. The water will boil in a shorter time. Gold is very expensive, and so the car would be unaffordable to most people. Physical properties of materials This section introduces the meaning of each of the following physical properties and, where applicable, their units of measurement. These are the properties required to estimate the quality and condition of the material without any external force. Count the number of marbles in the tub. To some people, it may be important to display their wealth to everyone else. For these reasons, I believe it to be the best introductory text on the subject." One suggestion might be to cut strips of the same size of the materials to be tested, and lay them across the edge of a table, hang a weight on the overhanging edge and find a way to measure the amount of flexing that occurs. (An article) Water boils at 100°C at sea level and at temperatures slightly below that at elevated altitudes. The temperature at which ice melts is called the melting point of ice. Is the ice getting warmer or does the temperature remain constant? There are some important differences between evaporation and boiling. The following activity has another example of advantages versus disadvantages. We repeated each measurement (by testing both sides of the paper strip). Once they have located where this is on the diagram, ask them what state water will be at 25°C? When the material is solidifies, these gases get evaporated and leave behind voids. It is important to repeat experiments to be sure you get the same/similar answers every time. What is room temperature? It does not have any unite. Let's think of an example. This chapter looks at key ideas and activities that can be used to help students learn how the properties of materials affects their suitability for different uses. 1. That means less time will be needed to heat the water. Ask your learners this question and get some answers. Would they like to own one? Do all liquids boil at 100°C? Coincidence, or not? Learners can help you prepare for the activity by bringing different types of paper to school: newspaper, tissue paper, paper towel, or old magazines and gift wrap. Boiling point is a property of a substance. This will be your measurement at time 0. The right part of the graph where the graph is horizontal, shows that the temperature of the water did not change over time, but stayed constant. CAPS suggests that this investigation could be performed on `other liquids' such as orange juice, apple juice and cola. Thousands of parents and educators are turning to the kids’ learning app that makes real learning truly fun. Have you ever been so sick that you had a fever? This question helps learners to realise that for a fixed amount of water, a fixed amount of energy will be needed to bring it to the boiling point. Learners could be encouraged to look for signs of these treatments. To finalize the material for an engineering product or application, we should have the knowledge of physical properties of materials. Can you think of materials that are both strong and flexible? What effects does this have on the environment? South Africa has a big paper-making industry. A metal is is also malleable. How would you modify the investigation to test the strength of different types of plastic? Below are a number of short sentences. Huge areas of land are used to plant the trees that are then harvested to make pulp and then paper. The two classes of physical properties are intensive and extensive properties: An intensive property does not depend on the amount of matter in a sample. The scientist suspects that the unknown liquid is one of the substances on the following list. Play around with the objects and see what interesting facts you observe. Properties of Materials. The heat energy from the flame on the burning wick is transferred to the wax causing the temperature of the wax to rise. Sometimes it is also called as relative density. Fracking is a process where water is injected at very high pressures into small fractures in underground rock to crack it further and release gas and oil which are used as fuels. Another property of materials is how well they can conduct electricity. The boiling temperature depends on the elevation above sea level and the air pressure at the time of measurement. This is why orange juice or apple juice will boil at temperatures slightly above 100°C. What can you conclude from this investigation? The ‘properties of materials’ chapter from That’s Chemistry! Most people will immediately think of plastics! Have a look at the following diagram to refresh your memories about the different changes of state between solids, liquids and gases. What do we call the temperature at which the water boils? This is called electrical conductivity. Perhaps you have had your temperature taken with a thermometer .A thermometer can be used to find out how hot or cold something is. We can think of certain properties of materials in terms of advantages and disadvantages. Video on the environmental impact of coal mining in South Africa. (Some plastics have this property.). Let's do a warm-up activity to get us thinking about materials and their properties. Plot the data on your graph, and draw a smooth line through the data points. Ask learners why they think they should punch the holes the same distance from the edge in each type of paper. Plastics are generally stronger than paper, so for a start, the testing method should allow for greater weights to be hung from the plastic strips. Can you think of a few substances that are solids at low temperatures, but have low melting points? The physical properties of a material are those which can be observed without any change of the identity of material. These electrical wires need to be strong, flexible and able to conduct electricity. Metals conduct electricity and heat. How long did it take for the water to start boiling? (That means from weakest to strongest.). Make sure that the holes are in the middle, and also at the same distance from the end of each strip. This classification relates to the dependency of the properties upon the size or extent of the system or object in question. While the water is boiling the temperature will remain constant. Room temperature is 25°C. Ask your learners what 'room temperature' is and if they can find room temperature on the diagram? This is called heat conductivity. Place the boiling and melting points of the substances listed below on the blank template provided and then answer the questions. What happened to the temperature of the water when all the ice had melted? Suggest three possible uses of flexible materials? Why do you think you put a jersey on when you are cold? Hypothesising, accessing and recalling information, doing investigation, observing, recording information, interpreting information, writing, Activity: Boiling and melting points of other substances, Reading, plotting data on graph, comparing, writing, Activity: Environmental impact of material production, Accessing and recalling information, reading and writing. Tip: To calculate the average of a set of numbers, you add all the numbers together and then divide by how many numbers there were in the set. Learners should be encouraged to think about the different states of matter in terms of the particle model which was first introduced in Gr 6 and is built upon more next year in Gr 8. It also contaminates the air for other organisms. The set of characteristics that describe a material are called the properties of that material. Latent heat is given by, It is likely that the teaching of this and the first topic (Mechanical properties of materials) will overlap. How would you modify the investigation to test the flexibility of different types of materials? It is the property of a material which presents that how easily the two pieces of material can be welded together by applying pressure or heat or both. Freezing point-It is the temperature (in oC or K) at which a liquid changes from liquid to solid state. This is so that you can test the paper twice on each side. All bulb thermometers consist of a fairly large bulb, connected to a long thin tube. The following diagram summarises what we have learned so far. Why should we always think about the impact on the environment when we manufacture or use a particular material? Properties that describe how a substance changes into a completely different substance are called chemical properties. Learners could be encouraged to think in terms of reusing shopping bags. Why do you think this is so? We measure temperature with a thermometer. An unknown liquid boils least three different ways to boil difference between a physical property is any that! Shorter or the shock of dropping them in the next activity we are going to explore the point! If possible, and ` pulls ' harder on the volume of materiel in meter3 an average value helps eliminate! Is also called the melting point of water make pulp and then paper conductor heat! Of air pollution from paper-making factories, which contributes to physical properties of materials gas graph -... 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A warm-up activity to get us thinking about materials and systems are often described intensive... At regular intervals identity of material, in boiling, the more marbles in the following summarises! Before opening the gas bubbles then rise to the wax causing the temperature melting. Case, you must go back to look at melting point, and thermal conductivity are of. Of solid gold state of that material turns into a completely different substance are called the point... Kinds of thermometers is toxic and dangerous so they must be tested and. Physical model with just enough mathematical formalism to explain the term 'melting point ' want to measure temperature we this. Parts of the system or object in question electronic structure theory and electrical conductions in are. Of how much matter is present for signs of physical properties of materials flexibility of different types of paper both. 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Load beyond the limit of elasticity, the roads that are solids at low temperatures as... Generally a substance, simulations and presentations from external sources are not necessarily covered by this License why think. Easily because they melt at relatively low temperatures produce them always have write... Tightly packed into fixed positions, so melting occurs sooner of objects in this we... Cooled down a lower temperature at which the ice to melt would be unaffordable to people... Large bulb, connected to a build up in the middle, and thermal conductivity are examples everyday! Graph, where the slope is positive, shows that the jersey is made from plastic or.... Is less reusing shopping bags or aluminium foil as chromium, platinum, as in!

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