chapter 2 notes ‘exploring diversity of matter by its physical properties .pdf

HILLGROVE SECONDARY SCHOOL SCIENCE DEPARTMENT SECONDARY ONE EXPRESS / NORMAL (ACADEMIC) CHAPTER 2: EXPLORING DIVERSITY OF MATTER BY ITS PHYSICAL PROPERTIES Name: T...

HILLGROVE SECONDARY SCHOOL SCIENCE DEPARTMENT SECONDARY ONE EXPRESS / NORMAL (ACADEMIC) CHAPTER 2: EXPLORING DIVERSITY OF MATTER BY ITS PHYSICAL PROPERTIES Name: Teacher’s Copy_ Class: 1 – ___ Date: ___________ By the end of this chapter, I can No. Learning Goals / 1 show an awareness of the importance of making informed choices of the appropriate and sustainable use of materials for household products (e.g., fibre, plastics, ceramics, metals and glass) based on their physical properties, e.g., demonstrate curiosity about the physical properties of things commonly encountered in daily life 2 classify a number of common everyday objects and recognise that there are many ways of classifying the same group of objects 3 evaluate the usage of different materials using data of their physical properties 4 communicate findings on classification and justify reasons 5 describe physical properties that can be observed or measured, e.g., electrical conductivity, thermal conductivity, boiling/melting point, *strength, *hardness, *flexibility and density (* Optional for NA) 6 estimate length, mass and volume 7 measure accurately length, mass and volume (including mass and volume of liquids and solids but not of gases) of matter using appropriate instruments (measuring tape, metre rule, digital calipers, measuring cylinder, electronic balance) and methods 8 *(Optional for NA) apply concepts of volume displacement to derive the volume of irregular objects 9 show an understanding of how mass and volume affect density 10 predict whether an object will sink or float by comparing its density with that of its surrounding medium 11 calculate density using the formula (density=mass/volume) and use the appropriate unit (e.g., g/cm3 or kg/m3) 12 show an appreciation of how reducing the use of non-sustainable materials by using alternative materials with similar properties helps to minimise environmental impact 1 1.1 Why is it Important to Know the Physical Properties of Matter? ❖ Given the diversity of things around us, it is important to classify things to recognise patterns and better understand the physical properties of matter. ❖ One way of classifying items is to group them based on the materials used to make them. ❖ There are five main classes of materials, namely ceramic, metal, glass, fibre and plastic Material Properties Ceramic Made from clay Poor electrical conductor Hard Can be moulded into shapes Does not corrode High melting point Fragile / Brittle Fabric Can be spun or woven into fabrics Able to absorb dyes Poor conductor of electricity Poor conductor of heat Metal Shiny Good conductor of electricity Good conductor of heat Can be moulded into shapes Can bend without breaking Glass Transparent Poor conductor of electricity Poor conductor of heat Can be moulded into shapes High melting point Fragile / Brittle Plastic Lightweight Corrosion-resistant Can be moulded into shapes Has low melting point Poor conductor of electricity Poor conductor of heat [Refer to AB 2.1.1 (page 33 – 36)] 2 1.2 What are Some Common Physical Properties of Matter? 1.2.1 Physical Properties ❖ The physical properties of a material are quantities that can be observed or measured without changing its composition. ❖ Fill in the table using the following terms Strength* Electrical Melting point Flexibility* conductivity Thermal conductivity Density Hardness* Boiling point Property Description 1. Electrical measure of how easily an electric current flows through the conductivity material  electrical conductor: material that allows electricity to pass through readily (eg copper and iron)  electrical insulator: material that do not allow electricity to pass through readily (eg. plastic and rubber) 2. Thermal measure of how readily heat passes through the material conductivity  heat conductor: material that allows heat to pass through readily (eg metal)  heat insulator (poor heat conductor): material that do not allow heat to pass through readily (eg plastic) 3. Melting point temperature at which a material changes from a solid state to the liquid state 4. Boiling point temperature at which a material changes from a liquid state to a gaseous state 5. Strength* ability of material to support heavy load without changing its shape permanently or breaking 6. Hardness* Resistance to wear and tear, and scratches a material can cut or scratch a material as hard as or less hard than itself opposite of hard: soft 3  7. Flexibility* ability of the material to:  bend without breaking  return to its original size and shape after bending 8. Density Amount of mass an object has in proportion to its volume. When comparing a wooden block and an iron block of the same shape and size, the iron block has a greater mass because there is more matter in the same volume. When comparing two objects, if one object is  Less dense: Object floats  Denser: Object sinks * Optional for N(A) 1.2.2 Choice of Material When choosing an appropriate material, some questions you may consider include: What purpose does this object serve? What is it used for? What physical properties does it need to have?  Does it need to be strong?  Does it need to be flexible or rigid?  Does it need to conduct electricity / heat? Checkpoint 1 1. Copper is sometimes used to make pots and pans. Which physical property of copper do the pots and pans make use of? A Shiny B Opaque C Good conductor of heat D Good conductor of electricity ( C ) 2. Which physical property of steel makes it good as a material for a kitchen knife? A Strength B Hardness C Flexibility D High density ( A ) [Refer to AB 2.2.1 (page 37 – 40)] & AB 2.2.2 (page 41 – 42)* Optional for NA] 4 1.3 How Do We Investigate the Density of Objects? 1.3.1 Determining Mass Mass is the amount of matter in an object. SI Unit: kilogram ( kg ) Other units: gram (g), milligram (mg) and tonne (t) Common instruments to measure mass: electronic balance or beam balance 1 kg = 1000 g Practice! Convert the following masses: (a) 25.8 kg = 25800 g (b) 1200 g = 1.2 kg 1.3.2 Determining Volume Volume is the amount of space occupied by an object. SI Unit: cubic metre (m3) Other units: cubic centimetres (cm3) Common instrument to measure volume: beaker, measuring cylinder, syringe, volumetric flask, pipette or burette.  Ensure reading is read at the meniscus, avoiding parallax error. 5 Let’s Practise! volume = 44.5 cm3 volume = 21.5 cm3 (a) Volume of Regular Objects Volume of regular solids can be calculated using the correct mathematical formulae. (Optional for NA Science) (b) Volume of Irregular Objects Volume of irregular solids can be measured by the concept of volume displacement. Method 1 – for small irregular-shaped solid 6 Method 2 – small irregular solid that floats Method 3 – Displacement can method (For large irregular object) 1 2 3 Fill a displacement can When the water stops Tie the piece of object to a with water and allow flowing, replace the string. Lower the object until excess water to flow container with a dry it is completely submerged. out into a container. empty measuring Measure the amount of water cylinder. displaced into the measuring cylinder. It is equal to the volume of the object. [Refer to AB 2.3.1A (page 43 – 46) & AB2.3.2 (page 49 – 50)] 7  Checkpoint 2 Calculate the volume of the hammer. Volume = 69.0 – 65.0 = 4.0 cm3 1.3.3 Determining length to calculate volume Instruments for measuring length Measuring tape: for lengths greater than 1 m or lengths that are curved. Metre-Rule : for lengths of up to 1 m; Commonly used in laboratories Digital Calipers:  For short lengths of up to 15 cm or 150 mm.  Also can measure internal and external diameters or depth of an object  Very accurate, up to 0.01 mm 8 1.3.4 Determining Density Density is defined as the mass per unit volume The mathematical formula is as follow: Mass Density = or Volume SI Unit: kilogram per unit cubic metre (kg/m3) Other unit: grams per cubic centimetre (g/cm3) Checkpoint 3 A toy car has a mass of 160 g. Its volume is 80 cm 3. Calculate the density of the toy car. Density = Mass/ Volume = 160/80 = 2 g/cm3 (a) A wooden block has a mass of 200 g. Find its density. Volume = L x B x H = 8 x 7 x 5 = 280 cm3 Density = Mass/ Volume = 200/280 = 0.714 g/cm3 [Note: non-exact answers to be rounded to 3 s.f., fractions are not accepted] (b) The wooden block floats, while the toy car sinks in water. Water has a density of 1 g/cm3. We can therefore conclude that an object can float on water if it has a lower density compared to water. [Refer to AB 2.3.1B (page 47 – 48)] 9 1.4 Floating and Sinking The density of an object affects its ability to float on or sink in water. When comparing two mediums, a less dense object will float on a denser medium. Let’s Practice! Arrange the items in increasing order of density. Cork, oil, plastic block, water, grape, syrup lowest density highest density Checkpoint 4 1 The density of a metal cube is found to be 5.6 g/cm 3. When a hole of volume 1 cm3 is drilled into the cube, the density of the metal A remains the same B increases C decreases D becomes 4.6 g/cm3 ( A ) 2 Which of the following material(s) will float in a jar containing a liquid of mass 180 g and volume 200 cm3? I. Plastic foam (0.08 g/cm3) II. Cork (0.25 g/cm3) III. Glass (2.5 g/cm3) IV. Copper (8.9 g/cm3) A I only B II and III only C I and II only D III and IV only. ( C ) Further Practice: [Refer to AB 2.4.1 (page 51 – 52) & AB2.4.2 (page 53 – 54)] 10 1.5 How Can Understanding the Physical Properties of Materials Affect Our Choices for Sustainable Living? A. Environmental impact of our actions In Singapore, solid waste is burnt at waste-to-energy plants to generate heat and electricity and save landfill space. Incineration ash and non-incinerable waste are then disposed of at Semakau Landfill. About 800 000 tonnes are sent to Semakau Landfill every year and the space is expected to run out by 2035. B. Improper Disposal Improper disposal can negatively impact or harm our environment. C. Conserving our Environment - Reduce, Reuse, Recycle (3R’s) Reduce We should choose to use reusable items over single-use items. For example, we can refuse plastic bags when shopping or bring our own utensils to pack our food instead of using disposable ones. Reuse We can reuse these items for the same or new purpose. For example, we can donate our old textbooks or reuse food containers from takeaways. Recycle If we absolutely have to dispose of it, sort them and recycle responsibly. It is important to adopt correct recycling habits. Only clean recyclable items made of glass, paper , plastics and metal can be placed in recycling bins! Self- Think about your everyday habits. What are two actions you can Reflection take to protect the environment and conserve limited resources? 1. 2. 11