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The liquid level will rise when the liquid expands. When lighting the burner, always light the match (or lighter) before opening the gas. Take some of the ice pieces and drop them into the beaker. It is denoted by ‘L’. The concept of making predictions in science investigations is introduced here. Avoid the misconception that cars are made entirely out of steel. Coefficient of Area Thermal Expansion The ways we use materials and the processes we use to produce them always have an impact on the environment. Gold is very expensive, and so the car would be unaffordable to most people. What do you think will happen to the liquid level in the thermometer when it is put into the refrigerator? Let's make some predictions. Allow learners to discuss how to test how strong a material is for a few minutes and come up with a few ideas. CAPS suggests intervals of 3 minutes, but shorter intervals will provide more data points to plot on the graph. The boiling temperature depends on the elevation above sea level and the air pressure at the time of measurement. Which properties are important when choosing a material for a particular use? We will be focusing on boiling and melting in this section. Flexible means supple and bendy; able to flex and bend. Get them to mark where it is on the diagram. Label the axis, and use minutes as units. The following diagram summarises what we have learned so far. The physical properties of a material are those which can be observed without any change of the identity of material. Cars have crumple zones to increase safety. What did it look like when the ice started to melt? Use the list to identify the unknown liquid. Learners could be encouraged to look for signs of these treatments. At first, the temperature of the ice-water-mixture stayed constant, then after all the ice had melted, the temperature of the water started to go up. Make a handle for the yoghurt tub, using the string. When the person tried to heat the water, the kettle melted as a result of contact with the flame/heat. Liquids take up less space when they are cold and more space when they are warm; we say they contract when they are cooled and expand when they are warmed. For a list of the 10 most serious environmental concerns of the 21st century, visit the website. Some learners may know that water boils at a temperature around 100°C (100 degrees Celsius), depending on factors such as altitude above sea level and atmospheric pressure. When a material is heated, it expands, due to which its dimensions change. The inside of the refrigerator is cold. Measure the temperature of the ice-water-mixture every three minutes. to personalise content to better meet the needs of our users. Water runoff can also contaminate water supplies. This does not mean that your measurements were incorrect. The suitability of a material for a certain use is also influenced by other factors such as its cost, its colour and its texture. A majorenvironmental concern at the moment is the proposal to start fracking in the Karoo. 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. Generally a substance has three states called – solid state, liquid state, gaseous state. The ice would melt in a shorter time, because the burner gives it more energy in a shorter time. 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 electrical conductivity. For example, if you had 5 marbles in the first attempt, and 3 marbles in the second attempt, the average will be calculated as follows: Therefore, the paper type could hold an average of 4 marbles. We will learn more about changes of state in Gr. We will look more at how different materials can be used as electrical insulators (meaning they do not conduct electricity well), later in the year. The phase transition between water and ice (liquid and solid water) always occurs at 0°C (in pure water). Italy. You could add that it could be insured against theft, but that insurance on a car this valuable would be very expensive. Physical properties are based on the laws of physics that describe mass, energy, force, light, heat, electricity, and other physical phenomena. Huge areas of land are used to plant the trees that are then harvested to make pulp and then paper. Bulk density is another important properties of building materials.The bulk density is … Suggest three possible uses of a material that is a good conductor of electricity. Can you think of materials that are both strong and flexible? An article on fracking in South Africa. Q is the amount of heat given to material in Joule. This will be your measurement at time 0. Density 5. Each of the environmental issues is accompanied by a short video. It is the property of a material by which it regains its original dimensions on removal of load or force. Let's find out. This will make it a fair test. Good conductors of heat can be used for making pots and pans, heating elements, etc. strips of different types of paper (20cm x 5cm). Some learners may also say that because it is so valuable, it might get stolen. 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 ________. The thermal conductivity of a material can be defined as “the amount of heat transmitted by unit thickness of material normal to the unit area surface in unit time when the temperature gradient across the material piece is unity in steady state condition”. Water which contains impurities (such as salt or sugar) boils at a higher temperature than pure water. Thermal expansion coefficients are of three types, namely-. No. Boiling point can be used to identify a substance. Time intervals would depend on the volume of water. It looks as if something has gone wrong here! For instance, we can describe a metal by saying that it is strong and durable. Refractoriness Be careful not to drop it or bump it against the bottom or sides of the beaker. The ‘properties of materials’ chapter from That’s Chemistry! Do they think it looks great? Materials that can be hammered into thin sheets are called _______. The boiling point of methanol is the same as that of the unknown liquid, namely 65°C. A material’s performance depends on its physical properties, and optimizing this is the most important way to reduce your product’s environmental impact. This is because wood and plastic are not good conductors of heat, unlike metal, and so you can pick up the pot easily. The animal may eventually die as a result. At what temperature do you think water will freeze? Its unit in SI system is watts per meter per K. It is the property of materials which represents that how easily the electricity can be conducted by the material. Punch a hole at both ends of each paper strip. This will make the liquid inside the thermometer contract. There are some important differences between evaporation and boiling. What are the advantages of having a car made of gold? Why do you say so? In this photograph, the 2010 World Cup Soccer Stadium can be seen in the centre. Look carefully at the picture below. Swirl the ice with a small amount of water for about 20 seconds and then measure the temperature of the ice-water-mixture in the beaker. These properties determine how these different materials are used. Papers in which the fibers are longer and more tightly packed are also stronger, and coating the paper with a super thin layer of plastic also adds additional strength. Mining in South Africa has been one of the main reasons for our development. Physical and Social Properties of Materials . The ice would melt at the same temperature because the melting point stays the same. Discuss this as a class and write some notes on the lines provided. (Learner must indicate this temperature on the graph. Is it different from the original temperature of the ice? A suggestion is to also number the pieces of paper so that learners can easily reference them and then use the number to place them in order of strength later on in the questions. Probably not! If each marble has a mass of 5 grams, work out the mass in grams that was needed to tear each strip of paper and write the number in the final column of your table. Water boils at a temperature of 100°C when the air pressure equals 1 atmosphere. 2. What are some of these? Not only the mining, but the use of coal in power stations has negative impacts. What do you notice about the temperature when all the ice has melted? 5 and have revised again here. [1 mark]. Have you ever had your temperature taken? Plot the data on your graph, and draw a smooth line through the data points. Write down your ideas from your discussion. 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. Melting occurs when a solid turns to a liquid. South Africa is still one of the top gold mining countries in the world. What is your hypothesis for this investigation? Latent Heat of a material is defined as the amount of heat required/released by change in unit mass of material from one state to another state (Phase change). 4. We used the same method to hang the marbles from the paper strip for all the different types of paper. Have a look at the following diagram to refresh your memories about the different changes of state between solids, liquids and gases. When we keep on increasing the load beyond the limit of elasticity, the material retains it molded state. This is called the normal boiling point of water. Hypothesising, 1.1 Physical properties of materials (5 hours), Activity: Thinking about materials and their properties, Accessing and recalling information, classifying and sorting, Activity: Advantages versus disadvantages, Accessing and recalling information, comparing, identifying problems and issues, writing. The unknown liquid starts to boil after approximately 40 minutes. A practical advantage is that gold doesn't rust. What did you see when the water started to boil? If you can, write them in the space below. (Ductile describes a material which can be drawn out into a wire.). Say why you think it is this substance. The bigger flame gives more energy to the water but does not affect the boiling point. Do you remember learning about the state changes in previous grades? TABLE 3.1 Physical Properties of Selected Materials at Room Temperature 5 TABLE 3.2 Physical Properties of Materials, in Descending Order 6 Titanium and aluminum are among the most commonly used metal for aircraft and aerospace applications; 7 FIGURE 3.1 Ratio of maximum yield stress to density for selected metals. The point of this extension would be to show that different substances have different boiling points. When water is boiled over a bigger flame, it will boil at the same temperature, namely 100°C (at lower altitude/at sea level). Discuss with your partner why you think this is happening to the wax. Note: Learners should notice that, even though the ice is starting to melt, the temperature remains constant. 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. We always have to weigh up the advantages against the disadvantages when we choose materials for a particular job. We have already seen how the use of materials, such as plastics and paper, has a negative impact on our environment, but what about their production? This is because they might have been calibrated differently. Note: Once again, this has been included to bring learners to the realisation that a fixed amount of energy will be needed to melt a fixed amount of ice. Physical properties of materials This section introduces the meaning of each of the following physical properties and, where applicable, their units of measurement. How can we explain the term 'boiling point'? Now look carefully at the torn edge. Boiling point-It is the temperature (in oC or K) at which the substance changes from liquid state to gaseous state. Water boils at a lower temperature at higheraltitudes (for example, on a mountain) because the air pressure is less. The first part of the graph is a horizontal line, then the graph goes up (the line has a positive slope). Diamond mines require huge amounts of diesel which produce greenhouse gases which build up in the atmosphere. An interesting video on a new type of 'concrete canvas' with varying properties. The material senses the force of an impact on the car and sends an electric charge to activate the airbag. (An article) http://www.bbc.co.uk/news/uk-14432401. Do you think the time required for the ice to melt would be longer, shorter or the same? It is a property of material which represents that how easily a material can flow in liquid state. When we want to measure temperature we use a thermometer. Shape memory 1. Specific heat of a material is defined as the amount of heat required to increase the temperature of unit mass of material by 1oC. This is why orange juice or apple juice will boil at temperatures slightly above 100°C. 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. Can you imagine your world without paper? Discuss this in class and get your learners' input. The mercury inside these kinds of thermometers is toxic and dangerous so they must be handled with care. Transmission cables for electricity, electrical wiring, electronic components for computers and other electronic equipment, electrical fencing (to protect property), etc. First, let's check if everyone knows that there is a difference between the words heat and temperature. This is a lot of detail and not necessary for the learners to know about at this stage. Heating the ice with a burner simply delivers the energy at a faster rate, so melting occurs sooner. Useful for school research/inquiry and for homeschooling . What is room temperature? Draw a black line at this temperature and label it. Note: The temperature of the ice-water-mixture should be the same as the original temperature of the ice. Can you think of at least three different ways to boil water? Theoretically it is equal to the melting point. Coefficient of softening 15. Water freezes at 0°C. 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. Possible hypotheses that learners could give include stating the boiling point of water that they might know from previous knowledge. What impact do you think this has on this area? Why should we always think about the impact on the environment when we manufacture or use a particular material? We will learn more about heat transfer later in the year. The temperature at which ice melts is called the melting point of ice. You could let the learners cut the paper into strips of 20 x 5 cm each, or you could do this beforehand to save time. (Tip: Place the marbles very gently into the yoghurt tub or the shock of dropping them in might tear the paper). It does not have any unite. The mixture is at room temperature to begin with. Where, ‘l’ is the initial length of object, ‘ΔV’ is the change in length, ‘Δt’ is the change in the temperature. Now draw a blue line at the boiling point of water and also label this line. Note: Learners may battle with this question so you can ask them if they think anything can grow or live on these dumps again? The change in volume of an object due change in temperature is related by “Coefficient of volume thermal expansion”. Use the space provided to draw your own table to record your results. Tell them to bring the biggest pieces they can find. 3. In this investigation, you will add the number of marbles together for each time you tested the paper strength (this was twice for each strip of paper) and then divide by 2 to calculate the average number of marbles that each piece of paper can hold before it tears. Look at this photo of a candle burning. Fire resistance 8. Any given material will melt and freeze at the same temperature. What is fracking? A safe way of heating ethanol or methanol to its boiling point is shown in the following diagram. Can you imagine a car made of solid gold? A metal is is also malleable. FALSE: Two alternative TRUE statements are possible: A scientist wants to determine the boiling point of an unknown liquid. We want things to be strong and to last long. Is it a straight line? Encourage learners to make their own notes as you are talking in class as this is a valuable skill. What other properties of metals do you remember? Say. Here is an optional, extension activity on how a thermometer works. 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