Integrated Science Notes 2024 Year 1 PDF

1OLP Integrated Science Notes 2024 Year 1 Chapter 1. Scientific Endeavour NAME Answers CLASS 1 INDEX NO. TEACHER 1 Contents...

1OLP Integrated Science Notes 2024 Year 1 Chapter 1. Scientific Endeavour NAME Answers CLASS 1 INDEX NO. TEACHER 1 Contents Page Glossary of Terms 3 Topic Outline 4 1.1 What is Science? 1.1.1 Perception of Science 5 1.2 Lab Safety and Apparatus 1.2.1 Safe Practices in Science 6 1.2.2 Hazard Symbols 7 1.2.3 Common Laboratory Apparatus 8 1.2.4 Bunsen Burner 10 1.2.4.1 Parts of a Bunsen Burner 1.2.4.2 Safety Precautions when using a Bunsen Burner 1.2.4.3 Types of Flames 1.3 How Do We Practice Science? 1.3.1 The Scientific Method 12 1.3.1.1 Identifying Variables 14 1.3.1.2 Observation vs Inference 15 1.4 Measurements 1.4.1 Physical Quantities & SI Units 16 1.4.2 Prefixes 18 1.4.2.1 Unit Conversions 1.4.3 Significant Figures 20 1.4.4 Measurement of Length 21 1.4.4.1 SI Unit and Instrument 1.4.4.2 Precautions using Measuring Tape/Metre Rule 1.4.4.3 Vernier Calipers 1.4.5 Measurement of Temperature 24 1.4.5.1 SI Unit and Instrument 1.4.6 Measurement of Time 25 1.4.6.1 SI Unit and Instrument 1.4.7 Measurement of Mass 26 1.4.7.1 SI Unit and Instrument 1.4.8 Measurement of Volume 27 1.4.8.1 SI Unit and Instrument 1.4.8.2 Measuring Volume of Solids 1.4.8.3 Measuring Volume of Liquids 1.4.8.4 Precautions when taking Volume Readings 1.4.9 Density 31 1.4.10 Accuracy, Precision & Uncertainty in Measure 33 1.5 Representing Data 33 1.5.1 Recording Data 33 1.5.2 Tabulation of Data 1.5.3 Presentation of Data 1.5.3.1. Line Graph 2 Glossary of Terms Term Description of term calculate to give a numerical answer, where, in general working should be shown (especially when two or more steps are involved) classify to group things based on common characteristics compare to identify similarities and differences between things or concepts construct to write or form something not by factual recall but analogy or by using given information describe to state in words (using diagrams where appropriate) the main points of a topic discuss to give a critical account of the points involved in the topics distinguish to identify and understand the differences between objects, concepts and processes evaluate to consider all factors relating to the object/event before making a judgement explain to give reasons or make some reference to theory, depending on the context identify to select and/or name the object, event, concept or process infer to draw a conclusion based on observations investigate to find out by carrying out experiments list to give a number of points or items without elaboration measure to obtain the quantity concerned directly from a suitable measuring instrument outline to give the main or essential points of the concepts or processes predict to state a likely future event based on the given information or rules recognise to identify facts, characteristics or concepts that are critical (relevant/appropriate) to the understanding of a situation, event, process or phenomenon relate to identify and explain the relationships between objects, concepts or processes show an to recognise and explain the importance of a concept or situation appreciation show an to show concern and perception in a particular situation or development awareness show an to recall, explain and apply information understanding state to give a concise answer with little or no supporting argument 3 At the end of this topic, you will be able to: Scientific Endeavour 1.1 What is Science? a) Shows an awareness that science is not confined to the laboratory, but is manifested in all aspects of our lives b) Shows a healthy curiosity about the natural phenomena in the world c) Shows an appreciation of science being a human endeavour, with scientific knowledge contributed by different civilisations over the centuries d) Understand the nature of scientific knowledge e) Understand how scientific knowledge is built from systematic collection and analyses of evidence and rigorous reasoning based on the evidence f) Shows an awareness that scientific evidence is subject to multiple interpretations 1.2 Lab Safety and Apparatus a) Observe laboratory safety rules in the Science laboratory b) Identify hazard symbols and describe their meanings c) Use the Bunsen burner appropriately and safely 1.3 How Do We Practice Science? d) Use scientific inquiry skills such as posing questions, planning and carrying out investigations, evaluating experimental results and communicating findings e) Recognise that scientific evidence can be quantitative or qualitative, and can be gathered through one’s senses or instruments as an extension of one’s senses f) Differentiate between observation and inference g) Distinguish between independent, dependent and controlled variables 1.4 Measurements h) State 4 (out of the 7) fundamental physical quantities – length, mass, time and temperature – use appropriate instruments to measure them and state their SI units i) Using prefixes (Mega kilo, deci, centi, mili, micro) j) Calculate derived units k) Calculate area, volume, speed, and state their S.I. units l) recall and apply the relationship density = mass / volume to new situations or to solve related problems. m) Describe the errors in measurements and how it can be reduced n) Show an understanding of precision and accuracy associated with measurements 1.5 Representing Data o) Tabulate data p) Plot and interpret graphs 4 1.1 Nature of Science Science is the process of learning about the natural world through observations & experimentation. Scientific ideas are developed through reasoning. Scientists use evidence to support explanations about how the world works. A scientific theory is a well-substantiated explanation of some aspect of the natural world, incorporating facts, laws, inferences and well-tested hypotheses. identifying patterns in nature and Science is the process of developing explanations of how and why those patterns exist. Scientists use experimentation and careful observation to collect evidence to support those explanations. 5 1.2 Lab Safety and Apparatus 1.2.1 Safe Practices in Science These are some safe practices to adopt when in the lab. General Safety Rules Chemical Safety  Follow all instructions!  Never touch, taste, or smell chemicals.  Never perform activities without the  Do not directly inhale chemicals. Waft them approval and supervision of the teacher. gently under your nose.  Absolutely no running!  Use only the chemicals needed.  Do not eat or drink in the laboratory.  Dispose of chemical as instructed by your  Keep work areas clean and organised. teacher.  Hair should be tied and long fringe pinned  Wash chemical spills with plenty of water. up.  Keep all containers closed when not in use.  Inform teachers of any allergies.  Always put on safety goggles when conducting experiments. Glassware Safety Heating and Fire Safety  Do not use chipped or broken glassware.  Keep all flammable materials away from  Never handle broken glassware with your flames. bare hands.  Do not heat substances in a closed  Never point a test tube toward yourself or container. another person.  Use tongs or cloth to handle heated  Throw broken glass into container labelled glassware. “BROKEN GLASS”.  Wear goggles when heating. First Aid After the Experiment  Report all accidents to your teacher, no  Clean up your work area. matter how small or minor you think it is.  Unplug all electrical appliances.  Know where these are located: First-Aid Kit,  Dispose of wastes as instructed by your Fire Extinguisher, Fire Blanket, Eye Wash teacher. Station, and Emergency Shower.  Wash your hands after every experiment.  Push back your stool.  Remove all your belongings from the lab. Animal and Plant Safety Using Sharp Instruments  Do not perform experiments that cause  Handle sharp instruments with care. harm or pain to animals.  Never cut material towards you; cut away  Inform your teacher of any allergies to from you. plants, molds or animals before doing an activity.  Wash your hands after handling animals, animal parts, plants, plant parts or soil. 6 1.2.2 Hazard Symbols  Hazard symbols are found on containers of chemicals to indicate the potential hazard it possess.  Each pictogram covers a specific type of hazard and is designed to be immediately recognizable to anyone handling hazardous material.  Familiarise yourself with the various symbols and identify the precautions to be taken. Symbol Symbol Harmful/ Irritant Toxic chemicals  Limit contact with  Keep food and drink away chemical. from handling areas.  May cause allergic  Wear suitable protective reactions when in contact equipment. with skin, eyes etc.  Wash hands after handling  Wash hands after handling chemicals. chemicals. Corrosive Flammable  Avoid skin contact.  Keep away from sources of  Wash hands after handling fire. chemicals. Explosives Toxic to aquatic life  Keep away from sources of  Avoid release to the fire. environment.  Ensure proper disposal. Carcinogenic (Cancer-causing) Gases under pressure  Wear protective gear.  Compressed, liquefied, or  Minimize contact with dissolved gas under pressure. chemical.  Keep away from heat.  Do not inhale any vapour/fumes. Radioactive Biohazard  Wear protective gear.  Wash hands after handling  Minimize contact with chemicals. chemical.  Wear protective gear.  Separate the radioactives  Ensure proper disposal. from non-radioactives. 7 1.2.3 Common Laboratory Apparatus Apparatus Diagram Apparatus Diagram Name: Bunsen burner Name: tripod stand Function: For heating Function: support the substances apparatus during heating Name: retort stand Name: wire gauze Function: support the Function: used with tripod apparatus during stand to support apparatus experiments during heating Name: Name: beaker (a) Test tube (a) (b) Boiling tube Function: to contain larger Function: contain small amounts of liquids or amount of substances for chemicals for heating or heating or mixing; or to (b) mixing; comes in various heat small amounts of capacities substances Name: gas jar Name: conical flask Function: used for holding Function: used for collection liquids or chemicals; of large volumes of gases suitable for reactions that involve swirling as it reduces spillage Name: measuring cylinder Name: syringe 5 0 4 0 3 Function: measure a volume 0 Function: used for 2 of liquid; comes in various 0 measuring small volume of capacities e.g. 10ml, 25ml, 1 liquid or gas; comes in 0 50ml various sizes 8 Name: burette Name: pipette Function: used to measure Function: used for accurately fixed volumes of dispensing precise volumes liquids; comes in various of liquids; smallest division capacities e.g. 20.0 ml 25.0 up to 0.1 cm3 ml Name: evaporating dish Name: filter funnel Function: evaporate a liquid Function: used to transfer from a solution by heating liquids into apparatus with small opening; support filter paper when carrying out filtration Name: glass rod Name: dropper Function: used for stirring Function: used to transfer reacting mixtures very small amount of liquids (drops) from 1 container to another Name: test tube holder Name: test tube rack Function: used to hold a Function: used for holding test-tube/ boiling tube test tubes before/ after while being heated they are used 9 1.2.4 Bunsen Burner 1.2.4.1 Parts a Bunsen Burner flame (outer cone) flame (inner cone) barrel gas tubing collar air hole gas tap base Part of Bunsen burner Function Air hole Allow air(oxygen) to enter the burner to mix with the gas. Collar Control the size of the air-hole. Barrel Keep the flame away from the gas jet / Allow the gas and air to mix Gas tap Supplies gas to the Bunsen burner Base Supports the Bunsen burner 1.2.4.2 Safety Precautions 1. Wear goggles when doing heating experiments. 2. Ensure that there are no flammable items near the flame. 3. Close air hole before lighting to prevent strike back. Strike back: Happens when there is too much oxygen is mixed with little gas, which causes the flame to burn at the gas jet, making the barrel of the Bunsen burner very hot. 4. When not using the flame, either a) turn off the gas supply to turn off Bunsen burner or b) close the air hole and lower gas supply 10 1.2.4.3 Types of Flames Luminous flame Non-Luminous flame  Obtained when air hole is closed  Obtained when air hole is opened - Little oxygen mixed with gas during - Maximum oxygen mixed with gas during burning (more incomplete combustion) burning (more complete combustion)  Orange in colour  Pale / light blue in colour  Unsteady / Flickering  Steady  Quiet flame  Noisy flame  Less hot (300°C, used for gentle heating or  Hotter flame (700°C, used for strong heating) warming)  Gives off little smoke (little soot produced)  Gives off a lot of smoke (produces lots of soot) 11 1.3 How Do We Practice Science? 1.3.1 The Scientific Method The Scientific Method is a sequence of steps that help a scientist answer those questions that lead to new discoveries. The scientific method is a procedure that leads an individual through the process of solving a problem. 12 The Scientific Method 1. Observation of phenomenon Observe your subject and record everything about it using your 5 senses. Include colours, timing, sounds, temperatures, changes, behavior, and anything that strikes you as interesting or significant. 2. State the question Propose a research question regarding what you want to find out about. 3. Conducting research Conduct background research to obtain more information about the matter that you are investigating. Write down your sources so you can cite your references. Interview experts on a topic. The more you know about a subject, the easier it will be to conduct your investigation. 4. Form a hypothesis A hypothesis is a tentative, testable explanation. Usually, a hypothesis is written in terms of cause and effect and includes the independent and dependent variable. Example of hypothesis: When the temperature of water is higher, the sugar takes a shorter time to dissolve. Non-example of hypothesis: Temperature of water affects dissolving a sugar. 5. Design an experiment Design and perform an experiment to test whether your hypothesis is true. - Identify the independent, dependent and constant variables. - Choose suitable apparatus and materials for the experiment. - Decide how to record the observations or measurements. - Write the procedure to describe how you will conduct the experiment. You can include diagrams of how the apparatus will be set up. 6. Data Analysis Record the data and observations and present it in an appropriate form (eg table, graphs etc). Ensure that all data (including anomalies are included). The data may need to be further analyzed such as by calculating the average to support your hypothesis. The trend or relationship between the variables can also be determined based on the data obtained. 7. Conclusion Based on the data analysis, conclude whether to accept or reject your hypothesis. There is no right or wrong outcome to an experiment, so either result is fine. 13 1.3.1.1 Identifying Variables  When you design an experiment, you are controlling and measuring variables. There are three types of variables: 1. Independent Variable: This is the variable that is being changed. To ensure a fair experiment, there should only be one independent variable. This is to ensure that any change in the results can be attributed to the changed variable. 2. Dependent Variable: This is the variable you measure. It is called the dependent variable because it depends on the independent variable. 3. Controlled Variables: These variables are the variables that are kept constant in all experiments. There can be many controlled variables, but one should always state the ones that must be kept constant to ensure that the results of the experiment is not affected by it. Eg: Experiment to determine the effect of bio-fertiliser X on plant growth Hypothesis: When fertilizer ‘X’ is used, the plant is able to grow taller. Independent variable: Addition of fertilizer ‘X’. Dependent variable: Height of the plant after 1 month Controlled variables: Volume of water used for watering plants, amount of sunlight plant is exposed to Read Textbook 1A, Pg 12 -15 14 1.3.1.2 Observation vs Inference  Observation is essential in science. Scientists use observation to collect and record data, which enables them to develop and then test hypotheses and theories.  Scientists observe in many ways – with their own senses or with tools like magnifying glasses, thermometers, satellites or stethoscopes. These tools allow for more precise and accurate observations.  Observations are made using our own senses or using scientific tools. Any data recorded during an experiment can be called an observation.  Inferences are ideas or conclusions based on what you have observed or already know. Observations are visible or provable facts. Inferences are opinions or conclusions based on observed facts. Inferences are guesses based on evidence (observations and prior knowledge). Observation is what you see and inference is what you figure out. 15 1.4 Measurements 1.4.1 Physical Quantities & SI Units What is a Physical Quantity? A physical quantity is a quantity that can be measured. It consists of a numerical magnitude and a unit. For example: Scientists use standard conventions for measurements to ensure effective communication of scientific ideas. In the past, the length of an object was measured by comparing it with some part of the body. Here are some examples. However, measuring by using the hand or foot was very inaccurate and confusing. Thus in 1960, scientists devised a system of units for the measurement of physical quantities. This was called the International System of Units (SI Units). The SI Units is based on the metric system of measurement and is used by scientists as the standard set of units for scientific measurement. All the physical quantities can be divided into base quantities and derived quantities. 16  1. Base quantities are physical quantities that cannot be expressed or defined from others. E.g. length, mass, time. 2. Derived quantities are physical quantities defined in terms of two or more base quantities. E.g. speed is a physical quantity derived from the base quantities of length and time. The 7 base quantities and 7 base SI units are shown in the table below. Base quantity SI base unit Symbol Other units length metre m µm, cm, km, inch, mile, feet mass kilogram kg gram, pound, stone time second s minute, hour, day, year temperature kelvin K C, F All other physical quantities can be derived from these seven base quantities. These are the derived quantities. Derived How derived units are SI derived unit Symbol quantity expressed in terms of base quantities area length x width square metre m2 volume length x width x height cubic metre m3 density mass ÷ volume kilogram per cubic meter kg/m2 speed distance ÷ time metres per second m/s acceleration change in speed ÷ time metres per second squared m/s2 Physical Quantities Base quantities Derived quantities Area Length Volume Mass Density Time Speed Temperature Acceleration 1.4.2 Prefixes 17 Instead of writing a long number with many zeros, we can use prefixes. Bacteria is very small, it is about 1 µm long. The Sun is 149.342 Gm (Giga meters) away from us. The use of prefixes enables us to reduce the 103 means 10 x 10 x 10 = 1000 number of zeroes. The table below lists the SI prefixes. 10-1 means 1 ÷ 10 = 0.1 Prefix mega kilo deci centi milli micro Symbol M k d c m µ Factor 106 103 10−1 10−2 10−3 10−6 Powers of Ten https://youtu.be/0fKBhvDjuy0 Cell Size and Scale https://learn.genetics.utah.edu/content/cells/scale/ 18 1.4.2.1 Unit Conversions To convert from kilo or mega to any unit, To convert from any unit to deci, centi, simply multiply by the factor milli or micro, simply multiply by the factor X factor X factor Mega (M) kilo (k) BASE UNIT deci (d) centi (c) milli (m) micro (µ) 1000 000 1 000 (g,m,s etc) 10 100 1 000 1 000 000 ÷ factor ÷ factor To convert from any unit to kilo or mega To convert from deci, centi, milli or micro to to, simply divide by the factor any unit, simply divide by the factor Steps to convert units: Step 1: Convert the unit given to the base unit. Step 2: Convert the base unit to the unit in question. Worked examples on expressing quantities in terms of SI units: 1) Express 2.35 cm in mm Step 2: Convert the base unit to the unit in question. Step 1: Convert to base x1000 unit (metres) first ÷100 2.35 cm = 0.0235 m = 0.235 mm 2) Express 0.338 km in cm x1000 x100 0.338 km = 338 m = 33 800 cm 3) Express 1.89 ml in l ÷1000 1.89 ml = 0.00189l 4) Express 0.0013 kg in μg x1000 x1000 000 0.0013 kg = 1.3 g = 1 300 000 μg 19  Change the following as indicated: (i) 1.2 km = ……1200……………. m (ii) 25 cm = …………0.25………………. m (iii) 2.6 km = ………260000………. cm (iv) 162 mm = …………16.2………. cm (v) 2 km = …………20 000….dm (vi) 135 mg = ………0.000135…… kg (vii) 3200 m = …0.0032…….Mm (viii) 45 Mm = ……45 000………. km (ix) 2.6 kg = ………2 600 000………. mg (x) 0.009 kg = ……9 000 000…… µg (xi) 300 mg = ……0.0003……. kg (xii) 1750 g = ………1.75…………. kg (xiii) 0.25 dm3 = …………250….. cm3 (xiv) 2234 cm3 = ………2.234…….. dm3 Read Textbook 1A, Pg 16 -17 1.4.3 Significant Figures Significant figures are important because they tell us how good the data we are using are. Rules for determining Significant Figures (1) All non-zero digits are significant: 359 has 3 significant figures, 1.234 has 4 significant figures, 1.2 has 2 significant figures. (2) Any zeroes after non-zero digits are significant: 205 has 3 significant figures. 508001 has 6 significant figures. 1000 has 5 significant figures 3.07 has 3 significant figures. (3) Zeros before a non-zero digits are NOT significant. 0.350 has 3 significant figures, 452.0 has 4 significant figures, 0.0070 has 2 significant figures, 0.0200 has 3 significant figures, The Significant Figure Rule (s.f. rule) In multiplication and division, the significant figure rule is to express the final answer with the smallest significant figure of the numbers being multiplied. 20 1.4.4 Measurement of Length 1.4.4.1 SI Unit and Instruments  The SI unit for length is the metre (m)  Some of the common instruments that we will use in school to measure lengths are: o Metre rule o Tape measure o Vernier Calipers  When measuring length, use an instrument suitable for the size of length to be measured that would give the highest precision. Different instruments are needed to measure different- sized objects. Length to be measured Suitable instrument Precision of instrument More than 1 m Measuring tape 0.1 cm Between 10 cm to 1 m Metre or half-metre rule 0.1 cm Between 1 cm to 10 cm Vernier callipers 0.01 cm Understanding the precision of an instrument  The precision of an instrument refers to the smallest measurement it can measure.  When recording a measurement, it has to be recorded according to the precision of the instrument.  Eg: Length measured Instrument used Recorded data 150 cm Measuring tape 150.0 cm 13 cm Metre rule 13.0 cm 4 cm Vernier callipers 4.00 cm 21 1.4.4.2 Precautions using Measuring Tape/Metre Rule (i) To prevent zero error: Measure from the 1.0 cm mark and then subtract 1.0 cm from the reading. The reason is that for most metre rules, the zero mark is at the very end of the rule, and so the wear and tear of the end of the rule may make the mark unsuitable for the use in measurement. (ii) To prevent parallax error: The eye must be positioned vertically above and perpendicular (at 90°) to the mark to be read when taking the readings. This is to avoid parallax error, which is the error in reading caused by the incorrect positioning of the eye. 1.4.4.3 Vernier Calipers  The Vernier Calipers has a precision of 0.01 cm.  A useful instrument to measure both internal and external diameters of objects.  It consists of a main scale and a sliding vernier scale.  The vernier calipers has outside jaws for measuring the external diameter of objects, inside jaws for measuring the internal diameters of tubes and containers and a depth bar to measure the depth of a container. Depth bar used to measure the depth of an object. 22  In the table below, identify the instruments used to measure length and answer the following questions Instrument What unit(s) does What length is State the precision of the the instrument the smallest instrument measure length in? division on the instrument? centimetres (cm) and 1 mm or 0.1 cm 0.1 cm millimetres (mm) Name: Metre rule centimetres (cm) and 1 mm or 0.1 cm 0.1 cm millimetres (mm) Name: Measuring tape Main scale: centimetres (cm) 0.1 cm 0.01 cm Vernier scale: millimetres (mm) 0.01cm Name: Vernier calipers 23 1.4.5 Measurement of Temperature 1.4.5.1 SI Unit and Instrument The SI unit of temperature is the kelvin (K) Another common unit used is the degree Celsius, °C The thermometer is used to measure temperature. Types of thermometer: a) Liquid-in-glass thermometer o Commonly used in the lab. The liquid in the thermometer is mainly alcohol. o The liquid expands or contracts as temperature changes and the length of the thread is calibrated to measure the temperature. o Precision: 0.5°C. (b) Other types of thermometers 24 1.4.6 Measurement of Time 1.4.6.1 SI Unit and Instrument  The SI unit for time is the second (s).  The stopwatch is used to measure short time intervals. The two types of stopwatches are: Analogue stopwatch reads up to ± 0.1 s (precision) Digital stopwatch reads up to ± 0.01 s (precision) more precise than an analogue stopwatch Reading the electronic stopwatch 2 min 39.54 s = (2 x 60) s + 39.54 s = (120 + 39.54) s = 159.54 s = 160 s (to the nearest second) Convert the following electronic stopwatch readings to the nearest second. a) 00 14 43 b) 01 37 89 c) 03 03 50 14 s 1 min 38 s = 98 s 3 min 4 s = 184 s While a stopwatch is started and stopped by hand, an error can be caused. This is called the human reaction time error and can be quite a large fraction of a second. The human reaction time is usually different for different people, but it is around 0.2 s for most people. Convert the following times: (i) 3.5 hours = …………210………. minutes (ii) 3.5 hours = …………12600………. second (iii) 2400 minutes = ………40……………. hours (iv) 400 seconds = …………6.67………. minutes 25 1.4.7 Measurement of Mass 1.4.7.1 SI Unit and Instrument The SI unit of mass is kilogram (kg) Unit used more frequently is the gram (g) The electronic balance is used to measure mass. The electronic balance has a precision of 0.01 g. Electronic Balance The electronic balance is used to measure mass but it actually measures weight and the value is electronically converted to mass. This instrument will only be accurate when used on Earth. Steps to use the electronic balance  Switch on the Power.  Press ‘TARE’ to zero the scale.  Place object to be weighed on the pan.  Close the plastic doors (if applicable).  Read off the display when it has stabilised. WHAT'S THE DIFFERENCE between mass and weight? Many people use these terms interchangeably, but that only works because we all live on Earth. If we start taking up residence in the moon or on other planets, we'll have to get more precise when we talk about how much stuff is in our stuff. Watch the video “Is Mass the Same as Weight?” (https://youtu.be/Y8-T8RouhPA) Mass is a measure the number of particles in an object. The SI unit of mass is kg. Weight is a measure of the force that gravity is pulling on the same object. The unit for weight is the Newton. [You will learn more about mass, weight and gravity in the next chapter.] 26 1.4.8 Measurement of Volume 1.4.8.1 SI Unit  Volume is the amount of 3-dimensional space occupied by a substance.  The SI unit of volume is the cubic metre (m3).  Other common units of volume are the cubic centimeter (cm3), Note: cubic decimeter (dm3), 1 dm3 = 1000 ml = 1000 cm3 = 1 l litre (l), 1 ml = 1 cm3 millilitre (ml). 1.4.8.2 Measuring Volume of Solids  For solid objects with regular shapes, we can calculate their volumes using a formula. The table below shows some examples of volumes of regular solids. Calculate the volume of the rectangular box below in m3. 1.0 cm 3.0 cm 12.0 cm Volume = Length x Breadth x Height = 0.12 m x 0.03 m x 0.01 m = 0.000036 m3  For solids with irregular shapes, we can determine their volume using the displacement of water method.  A measuring cylinder can be partially filled with water and the object is added to it. The difference in the volume of water is the volume of the object Vol of rock = 22 – 16 = 6 cm3 27 1.4.8.3 Measuring Volume of Liquids  Liquids can be measured using a syringe, measuring cylinder, pipettes or burettes, depending on the volume of liquid and the accuracy of the measurement. a) Beaker o Has different sizes and capacities. (eg 50 cm3, 250 cm3, 500 cm3 etc) o Is the least accurate apparatus to measure volumes. o Used to measure approximate volumes as its markings are far apart. o Readings recorded to whole numbers. b) Measuring cylinder o Has different sizes and capacities. (eg 10 cm3, 50 cm3, 100 cm3) o Is able to measure volumes more accurately than a beaker. o Precision of measuring cylinders range from 0.2 cm3 to 1 cm3, depending on the size of the measuring cylinder. o The zero marking of the measuring cylinder starts from the bottom as we are measuring the volume of liquid that is contained in the measuring cylinder. c) Syringe o Used to measure various volumes of liquid. o When drawing the liquid, no bubbles should be trapped in syringe bottom ring the syringe. eye level top ring o The level of liquid should be read at the top ring as shown liquid level in the diagram. eye d) Burette o Can measure volumes of liquid accurately. o Has a precision of 0.05 cm3. o Unlike the measuring cylinder and beaker, the zero scale on a burette is written on top. This is because the burette reading tells you how much liquid has been dispensed, instead of telling you how much liquid the burette contains. o First, it is filled to a predetermined level and the valve is opened to let liquid flow out. After the valve is closed, the difference in levels would be the volume of liquid dispensed. valve Initial reading: 0.20 cm3 Final reading: 22.20 cm3 Volume of liquid dispensed = 22.20 – 0.20 = 22.00 cm3 28  e) Pipette o Can be used to measure volumes of liquid accurately. o Pipettes can measure specific volumes depending on the size of the pipette. o Precision of pipette: 25.0 cm3 o It is usually used in conjunction with a pipette filler which helps to draw the liquid up into the pipette. 1.4.8.4 Precautions when taking Volume Readings  When measuring liquids in tubes, the surface of the liquid on top is not straight. It is slightly curved and this curved part of the liquid that forms is called a meniscus. 1. Take readings from the bottom of meniscus at eye level. 2. Apparatus such as measuring cylinders must be placed on a flat surface while burettes, pipettes and thermometers must be held vertically upright when readings are being taken. Incorrect reading (too high) 20.4 Correct reading ml 20.3 (same level) ml 20.1 Note: if the bottom of the meniscus ml Incorrect reading lies between two lines, then the (too low) reading obtained also be half of the lower and upper reading. State the volume of liquid shown below and whether it is a measuring cylinder or burette: Reading: 24.20 cm3 6.35 cm3 49.00 cm3 83.0 cm3 Measuring Burette Measuring cylinder burette Measuring cylinder cylinder/ burette 29 Instruments for measuring volume- Summary Beaker Measuring cylinder Burette Pipette Purpose - Least accurate and precise Measures volume of liquid it Measure the volume of Measures fixed volume of apparatus to measure contains, and can also liquid dispensed from liquid it contains, and can approximate volumes of dispense the same volume, the tap. also dispense the same liquids though not as easily as a volume 0 cm3 mark is at the top burette. - Can be used to measure of apparatus 0 cm3 mark is at the bottom large volumes of liquids of apparatus Capacity Various (50 cm3, 100 cm3, 10.0 cm3 50 cm3, 100 cm3 50.0 cm3 Various (The one in our lab 250 cm3 etc) is 25.0 cm3) Precision of instrument Not meaningful 0.2 cm3 1 cm3 0.1 cm3 0.1 cm3 (smallest division) There is only one marking on instrument Precision of readings Whole number Nearest Nearest 0.5 cm3 Nearest 0.1 cm3 recorded 0.1 cm3 0.05 cm3 Accuracy Not accurate Accurate Very Accurate Very Accurate 30 1.4.9 Density  Density is defined as the mass per unit volume.  The symbol used to represent density is ρ (rho).  Density has units of kg/m3 or g/cm3. This can be represented by the equation Effects of density Density of solid is greater than Density of solid is the same as Density of solid is lower than density of liquid  solid sinks density of liquid  solid will be density of liquid  solid floats suspended Watch Video: Archimedes and the Gold Crown https://www.youtube.com/watch?v=KMNwXUCXLdk Watch video: Density Facts https://www.youtube.com/watch?v=zlkpZZW29b0 1. Consider a cube of wood and a cube of metal of the same volume. State which cube is denser and suggest why it is so. ………………………………………………………………………………………………..................…………………………………………… …………………………………………………............................…………………………………………………............................... 2. A student fills a cup with 100 cm3 of water. She then adds 20 cm3 of syrup. If the density of the water is 1.0 gcm-3 and the density of syrup is 1.6 gcm-3, determine the density of the syrup drink that the student has mixed. 31 3. Complete the following table. Material Mass / g Volume / cm3 Density / (g/cm3) Air 1 000 0.0012 Styrofoam 1 000 000 0.045 Oil 60 000 0.80 Oak / Teak (wood) 30 000 0.75 Lithium (metal) 50 0.53 Aluminium 500 2.7 Iron / steel 20 000 7.9 Copper 50 8.9 Lead** 1 500 11.3 Mercury 0.5 13.6 Gold 150 19.3 The anomalous nature of water FYI In normal situations, when a substance is heated, it expands and when cooled, it contracts. The anomalous expansion of water is an abnormal property of water whereby it expands instead of contracting when the temperature goes from 4o C to 0o C, and it becomes less dense At 4oC, water has its highest density and contracts as the temperature rises from 0oC to 4oC. This means that in regions where winter is severe, lakes cool at the surface and when the water reaches 4oC and that water being denser will sink so water that freezes, will be at the surface. 32 1.4.10 Accuracy and Precision  Accuracy and precision (reliability) of data are important concepts, as they relate to any experimental measurement that you would make. This target has been struck with a high degree of precision, yet a low degree of accuracy. This target has been struck with a high degree of accuracy, yet a low degree of precision.  Accuracy - is concerned with how close a reading is to the ‘true value’ of an experiment.  Precision refers to how close the readings are for an experiment.  The accuracy and precision depends on the equipment used (eg beaker vs burette), the experimenter’s skill and the techniques involved.  In choosing different instruments for measuring the same physical quantity e.g. length, the data recorded will reflect the degree of precision.  In Science, both accuracy and precision are important!  How to increase accuracy in an experiment: o Repeat the experiment multiple times to obtain an average reading. This way, the average reading is closer to the true value.  How to improve precision in an experiment: Use an apparatus with a higher degree of precision; eg using burette instead of measuring cylinder Read Textbook 1A, Pg 16 - 24 For theories to be developed and then tested, it is necessary to make measurements, interpret the data obtained, refine the techniques used, employ higher precision instruments and repeat the measurement a few times and in different ways. We wish that every reading we are taking is the accurate value of the quantity we want to measure. We know that this is impossible because (a) the instrument used may have inherent defects, (b) we are humans and are prone to make mistakes, and (c) we do not know the exact ‘true’ value of the quantity we are measuring. 33 Understanding How Calculating the Average Increases Accuracy Take the swing of the pendulum for example. You would use a stopwatch to time the swing of the pendulum. You will notice that your results will vary each time you repeat your experiment. However, after taking, say, 4 readings, you will notice that, though the readings are different, they are hovering around a certain value. Though you will never know the TRUE value of the time taken for the swing, you can confidently conclude that the values obtained by your measurement are quite close to the true value. You can also say that repeating the measurements many times, e.g. 50 times, the AVERAGE VALUE obtained will be very close to the true value. Understanding the Impact of the Choice of Instrument Instrument Metre rule Vernier Caliper Reading 1.2 ± 0.1 cm 1.21 ± 0.01 cm Decimal places 1 2 It can be seen that the degree of precision increases from the metre rule to the Vernier Caliper. The number of decimal places also increases – from 1 to 2. In fact, the number of decimal places in a measurement gives an indication of the precision of the measurement. The choice of any instrument is only one of the factors affecting the accuracy of a reading. One may use a high precision instrument in measurement but if poor experimental techniques are used, the degree of accuracy of the reading and the confidence of the reading taken by the experimenter will be affected. Thus to optimize accuracy, the choice of instrument AND the techniques of measurements are important. Experimental techniques must reduce, not eliminate, any uncertainties in readings. average increases the accuracy of Note: Taking multiple readings and obtaining an the measurement but DOES NOT increase the precision of the measurement. The precision only depends on the instrument used. 34  1.5 Representing Data 1.5.1 Recording Data After observations and measurements are made, the information obtained needs to be presented in a manner that is useful and meaningful. 1.5.2 Tabulation of data  numerical data collected should be presented in a table format.  a table is able to summarize large amounts of data into something that is smaller and easy to read  a table consists of rows and columns Eg: In an experiment to determine the effect of temperature on the rate of dissolving, the temperature of water was measured before adding sugar, and the time taken for the sugar to dissolve is measured. Independent variable: Temperature of water Dependent variable: Time taken for sugar to dissolve In this experiment, the data recorded can be presented in a table as shown in the table below. Features of a table Each column has a relevant heading and unit to indicate the variable measured Data is organised into and also the unit used. columns, where each column represents 1 variable Temperature/°C Time taken / s 36.5 43 65.0 21 Note: The independent variable should be in the first column 1. Data recorded in the table should not have any units. 2. Data recorded should follow the precision of the instrument. * In Physics, the “Solidus method” is adopted. Symbols are used to represent quantities. e.g. Let temperature= T/° C Let time taken= t/s The heading of the table would therefore change accordingly; T/° C and t/s 35 Example Kyleen conducted an investigation to determine how much a spring extends as she increases the mass of the load. DRAWING OF SET-UP spiral metre-rule spring slotted mass (load) The results of the experiments are shown below. Dependent variable Independent with unit separated variable in first with a slash. column with unit. Mass of load / g Length of extension / cm 0 0.0 50 3.1 100 6.2 150 9.5 200 11.8 250 15.4 300 18.5 Readings follow the degree of Data is recorded without precision of the instrument any units. used to measure them. In this case it is a ruler with a precision of 0.1 cm 36 1.5.3 Presentation of data  After the recording of data, one needs to analyse the data to look out for trends, relationships etc.  For data analysis, it may be easier to make sense of the data by using graphs or charts.  In Science, we often use a line graph to determine the relationship between two variables.  Data that is gathered can be displayed as a: 1. pie chart 2. bar graph 3. histogram 4. leaf and stem diagram 5. line graph You will learn more about the other graphs in Math later in the year. We shall focus just on line graph for the moment. 1.5.3.1 Line graph  Used to show information that changes over time or the relationship between 2 variables  The line graph comprises of two axes.  horizontal axis is known as the x-axis (independent variable) while  vertical axis is the y-axis (dependent variable)  To indicate the axis of a graph, it is often written as “graph of y axis against x axis”. Plotting of line graph [SPLAT]  Scale: the graph (1st point to last point) must cover more than ½ the graphing area. - The scale needs to be consistent  Points are correctly marked with a small ‘x’.  Line of best fit is drawn- either straight line or smooth curve passing through as many points as possible; not ‘joining the dots’. Features of line of best fit: - should be a smooth line or curve (DO NOT SKETCH!) - lies very close to the points - has an approximately equal number of points above and below the line  Axes are correctly plotted and labelled. - Axes must be correctly labelled (follow the headings in the table) and the precision of the values must also follow the precision of the table.  Title of graph is written at the top: [‘Graph of y against x’] https://www2.nau.edu/lrm22/lessons/graph_tips/graph_tips.html#:~:text=The%20Axes,are%20(0%2C0). 37  Format for title: 5 Graph of Y-axis/ units Y-axis label 4 against X-axis/units with units Graph of time/s against length of pendulum/cm _ Time/s  180 Setting the axes and scale: - Draw the X-axis and Y-axis 1 - Each axis is drawn on a bold line for easy reading 160 - Choose an appropriate scale  and mark every big square according to the precision in the table 2 140 Plot your points: - Use a sharp pencil - Mark with ‘x’  - Check that points are plotted accurately 120 100  3 80 Drawing the line of best fit: - Draw a STRAIGHT line - Use a sharp pencil - The line should go through as many  data points as possible 60 - Line of best fit need not go through all the points. - Points, however, should be evenly distributed i.e. same number of plots above the line as below. 40  3 Line should exceed the first/ last 20 point by 1 cm 4 X-axis label with units Origin is always labelled. 0 10 20 30 40 50 60 Length of pendulum / cm 38  Integrated Science Notes 2024 Year 1 Chapter 2. Models – Kinetic Particle Theory NAME TEACHER CLASS 1 INDEX NO. TEACHER 1 Contents Page Glossary of Terms 3 2.1 What is a Model? 2.1.1 Why do we Build Models? 5 2.1.2 How do we Build Models? 7 2.1.3 Advantages and Limitations of Models 10 2.2 The Particulate Nature of Matter 2.2.1 Kinetic Particle Theory 11 2.2.2 Classification of Matter 11 2.2.2.1 Arrangement and Movement of Particles in matter 12 2.2.2.2 Using the KPT to explain behaviour of substances at 13 different states 2.2.3 Changes in States 15 2.2.3.1 Evaporation vs Boiling 15 2.2.3.2 Heating and Cooling Curve 16 2  Glossary of Terms Term Description of term model A physical / mathematical / conceptual representation of a system, object, or event / process. matter Anything that has mass and takes up space. particle Building block of matter. change of The conversion from one physical state to another, usually by a change in the energy of state the particles in the substance melting The process by which a solid turns into a liquid at its melting point. melting point Temperature at which a solid begins to melt. boiling The process by which a liquid turns into a gas at its boiling point. boiling point Temperature at which a liquid begins to boil. condensation The process by which a gas turns into a liquid. freezing The process by which a liquid turns into a solid. sublimation The process by which a solid turns directly into a gas without melting evaporation The conversion of a liquid to its vapour below the boiling temperature of the liquid deposition When a gas turns directly into a solid. 3  Unifying Ideas Visualising what we cannot see A model is used to help scientists visualise things that they cannot see. Scientific models are representations of objects, systems or events and not the actual thing. A model can be a useful tool not only for gaining understanding of the system but also for conveying it to others, and often allows the development and testing of hypotheses, and predictions of how real phenomena develop. At the end of this chapter, you will be able to: Understand why scientists use models List the different types of models and give examples of each Understand how models are developed State the advantages and limitations of models Kinetic Particle Theory (a) Show an awareness of the particulate nature of matter being a model representing matter that is made up of small discrete particles in constant and random motion (b) Describe the arrangement and movement of particles in matter in the solid, liquid and gaseous states using the particulate nature of matter (c) Explain their conversions of the three states of matter using models (d) Describe the difference between boiling and evaporation (e) Explain expansion and contraction, and the conservation of mass during these processes using models (f) describe some effects and applications of expansion and contraction in everyday life (g) Draw and interpret the heating and cooling curve* (h) Explain the changes in temperature associated with the heating and cooling curve* 4  2.1 What Is a Model? 2.1.1 WHY DO WE BUILD MODELS? Some models of the solar system are shown in the photographs below. Why do we build models? Write down some of your thoughts in the space below. As teaching tools e.g. in Science Centre To show how things work / how a process occurs To show details that we cannot usually see To predict future events To simulate events e.g. model of the spread of an infectious disease Write down other examples of models that you have come across in the space below. Model of a cell How earthquakes happen Globe models Architectural models 5 Scientific models are representations of objects, systems or events and are used as tools for understanding the natural world. A scientific model is a physical and/or mathematical and/or conceptual representation of a system of ideas, events or processes. Scientists build models to help them understand how something works, what it looks like, or how its parts interact. A model is used to help scientists visualise things that they cannot see. Models are useful simplifications to aid understanding and can help scientists communicate their ideas, understand processes, and make predictions. The table below shows examples of what models can represent. Models can represent... Example objects that are too small to see Model of an atom or a cell objects that are too big to see Model of the planets objects that no longer exist Model of a dinosaur objects that have not yet been discovered / Animal or plant / Prototype models of a robot invented events that occur too slowly to see Model of plant growth events that occur too fast to see Model to predict an earthquake events that have yet to happen Models of extinction of animals or loss of habitat Types of Models 1. Physical Models These are models that you can see and touch. Physical models show how parts relate to one another and can also be used to show how things appear when they change position or how they react when outside forces act on them. Examples include a model of the solar system, or a model of the cell. 2. Mathematical/ Computer Model A mathematical model is made up of mathematical equations and data. Simple mathematical models allow us to make calculations e.g. time taken for an object to hit the ground. Computer models can help predict the weather based on the motion of air currents, or in modelling events that take a long time to occur e.g. rise in sea levels. 3. Conceptual Model Conceptual models make comparisons with familiar things to help illustrate or explain an idea. Conceptual models can also be a system of ideas. One such example is the classification system used to classify living things. In the classification system, scientists group organisms by similarities. Such a model provides an easy way to think about the relationship of different animals through their classification. 6 Teacher Reference In science, a model is a representation of an idea, an object or even a process or a system that is used to describe and explain phenomena that cannot be experienced directly. Models are central to what scientists do, both in their research as well as when communicating their explanations. Models are a mentally visual way of linking theory with experiment, and they guide research by being simplified representations of an imagined reality that enable predictions to be developed and tested by experiment. Why scientists use models Models have a variety of uses – from providing a way of explaining complex data to presenting as a hypothesis. There may be more than one model proposed by scientists to explain or predict what might happen in particular circumstances. Often scientists will argue about the ‘rightness’ of their model, and in the process, the model will evolve or be rejected. Consequently, models are central to the process of knowledge-building in science and demonstrate how science knowledge is tentative. Building a model Scientists start with a small amount of data and build up a better and better representation of the phenomena they are explaining or using for prediction as time goes on. These days, many models are likely to be mathematical and are run on computers, rather than being a visual representation, but the principle is the same. Using models for predicting In some situations, models are developed by scientists to try and predict things. The best examples are climate models and climate change. Humans don’t know the full effect they are having on the planet, but we do know a lot about carbon cycles, water cycles and weather. Using this information and an understanding of how these cycles interact, scientists are trying to figure out what might happen. Models further rely on the work of scientists to collect quality data to feed into the models. To learn more about work to collate data for models, look at the Argo Project and the work being done to collect large-scale temperature and salinity data to understand what role the ocean plays in climate and climate change. For example, they can use data to predict what the climate might be like in 20 years if we keep producing carbon dioxide at current rates – what might happen if we produce more carbon dioxide and what would happen if we produce less. The results are used to inform politicians about what could happen to the climate and what can be changed. Another common use of models is in management of fisheries. Fishing and selling fish to export markets is an important industry for many countries including New Zealand (worth $1.4 billion dollars in 2009). However, overfishing is a real risk and can cause fishing grounds to collapse. Scientists use information about fish life cycles, breeding patterns, weather, coastal currents and habitats to predict how many fish can be taken from a particular area before the population is reduced below the point where it can’t recover. Models can also be used when field experiments are too expensive or dangerous, such as models used to predict how fire spreads in road tunnels and how a fire might develop in a building. 7  Science seeks to create simple descriptions of and explanations for our complex world. A scientific model is a very powerful and common way to represent these. When a scientific model enables us to make predictions it is more valued. As scientific models are representations of simplified explanations, they do not seek to explain every situation or every detail. This means that scientific models often are not identical with the ‘real world’ from which they are derived. Scientists seek to identify and understand patterns in our world by drawing on their scientific knowledge to offer explanations that enable the patterns to be predicted. The most useful scientific models will possess: explanatory power (a model that contributes nothing to explanations is of very little value) predictive power (the testing of predictions derived from the model is fundamental in establishing the robustness of the model) consistency across contexts (the model of an atom is the same when considering an atom of lead or an atom of gold) consistency with other scientific models (the model of an atom is the same for atoms in metal as it is for atoms found within a biological cell; the biological cell is another scientific model). How do we know if a model works? Models are often used to make very important decisions, for example, reducing the amount of fish that can be taken from an area might send a company out of business or prevent a fisher from having a career that has been in their family for generations. The costs associated with combating climate change are almost unimaginable, so it’s important that the models are right, but often it is a case of using the best information available to date. Models need to be continually tested to see if the data used provides useful information. A question scientists can ask of a model is: Does it fit the data that we know? For climate change, this is a bit difficult. It might fit what we know now, but do we know enough? One way to test a climate change model is to run it backwards. Can it accurately predict what has already happened? Scientists can measure what has happened in the past, so if the model fits the data, it is thought to be a little more trustworthy. If it doesn’t fit, it’s time to do some more work. This process of comparing model predictions with observable data is known as ‘ground-truthing’. For fisheries management, ground-truthing involves going out and taking samples of fish at different areas. If there are not as many fish in the region as the model predicts, it is time to do some more work. A model is an imagined way of carrying out an activity, or explaining how something will happen and why. Essentially it is a future vision about how something is intended to work and what might happen. We use models to guide and steer our behaviour all the time in everyday life. We also constantly change these models as we factor in new evidence to produce a better model. This is the important thing about models; they are works in progress, not cast in stone but constantly being tweaked to give more accurate and reliable projections. As such, models are never finished. 8 2.1.2 HOW DO WE BUILD A MODEL? Activity 1: Mystery Tube Your group is given a Mystery Tube made out of a toilet paper roll with the ends of 4 strings extending from 4 holes in it. The extensions are labelled A, B, C and D. Your task is to deduce how the strings are arranged or tied inside the tube. Explore the tube by pulling on each end, and observe carefully how it affects the other ends. Make a drawing of your group’s thinking of how the strings are possibly arranged/tied in the tube in the box below. You may want to draw more than one possible way. 9 Your group has just made a hypothesis. Remember that a hypothesis is a tentative, testable explanation about the natural world. It is not a prediction e.g. predicted result of an experiment. It is based upon the observations you made through your exploration. How confident are you about your hypothesis? How can you test out your hypothesis? After your model building activity, write down 2 things about what you now understand about how science works. E.g. Models are useful because…. 1. ………………………………………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………………………………………. 2. ………………………………………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………………………………………. 10 Teacher Reference Make the mystery tubes as follows: Suggestions on how lesson can proceed: Give a mystery tube to a group of 4 – 5 students. Remind them that they cannot open the tube to look inside. The task is to figure out how the strings are arranged or tied inside the tube by pulling on the each end in turn, and observing what happens to the other strings. Give them a few minutes to explore, and to discuss their ideas. Provide a mystery tube for group. Explain to them that their goal is to determine what the interior construction of the tube could be. Allow sufficient time for groups to work with the mystery tubes. Ask the students to draw their ideas (preferably more than 1) as to what the interior of the tube looks like. Walk around and encourage students to test their ideas and ask how they might do so. Once all students feel that they have a "solution," have each group share their findings with the rest of the class. You may have them post their drawings for others to view. This can lead to a form of "peer review" in which students can ask questions of each other. Explain to students that scientists almost always work in collaboration with other scientists, asking questions of one another, changing their ideas based on what others have found, building on one another’s work. Ask students how confident they are that their solution is correct. You may ask them to hold up five fingers for very confident, one finger for not so sure. Ask them what they might do to further test their ideas and to increase that level of confidence. Invariably someone will suggest making a model. This is where the toilet paper rolls come in handy. Hand out some items for building models in a packet: empty toilet paper roll, scissors, paper punch, buttons, string, beads, rings, paper clips to each group of students. Allow sufficient time for students to build their models and to see if they behave the same way that the Mystery Tube does. Have students share their models and discuss their effectiveness and how those models either support or refuted their original ideas. Discuss other areas of science in which models are used in a similar way — e.g., the structure of an atom. Explain that what they are doing is making a model of their mystery tube. Their understanding of the mystery tube is improved by making a model; once their model does what the real mystery tube does, they can have better confidence about their hypothesis. Also, different groups may have different models that could explain the observations. Sometimes competing explanations may be able to explain phenomena equally well. But it could also be that some explanations may fit the observations better. Communication about 11  observations and interpretations is very important among scientists because different scientists may interpret data in different ways. Hearing someone else’s views can help a scientist revise his or her interpretation. Ask: Did your views change during the discussions based on what others said? Do not allow students to open the tube, so you could continue with the metaphor about how scientists work: Scientists are often faced with situations that are a bit like the mystery tube, where they cannot observe things directly. Hence, they make models that emulate what the real thing they are studying does. Once their model accurately reflects reality, they know they can have greater confidence about their understanding of the reality. And at the end of model building, they would still not be able to open up the tube, just as scientists in the real world often would not be able to suddenly “open up the tube” and observe what they were not able to observe at first. 12 The flowchart below shows an approach that can be used to develop a model. Models may be revised as new data and evidence is discovered. Check the accuracy and Experimental Carry out a precision of the evidence from preliminary test measurements. Repeat the observation or experiment if the results are measurements not precise or accurate. 1st hypothesis Simple model New Carry out a experimenta second test l evidence 2nd hypothesis Revised model New Carry out a third experimenta test l evidence The process repeats, until a model is produced that satisfies each different set of experiments or explains each case 13 2.1.3 Advantages and Limitations of Models 1. Details — Models cannot include all the details of the objects that they represent. For example, the cell model does not include all the details of all the different types of cells found in all living things. 2. Approximations — Most models include some approximations as a convenient way to describe something that happens in nature. These approximations are not exact, so predictions based on them tend to be a little bit different from what you actually observe. Models do not behave exactly like the things they represent. 3. Accuracy — In order to make models simplistic enough to communicate ideas some accuracy is lost. For example, ball and stick models of atoms do not show all the details that scientists know about the structure of the atom. In the following topics, we will study some models that we use in Science to understand the world. For each of these topics, think about how the models help us understand what the world is made of how the models help us explain what we observed in living and non-living systems in particular, changes in state and the movement of substances the limitations of each model 14 2.2 The Particulate Nature of Matter 2.2.1 KINETIC PARTICLE THEORY (KPT) Kinetic Particle Theory (or Model) states that all matter is made up of tiny particles that are in constant random motion and constantly collide with one another. Remember, a scientific theory is a well-substantiated explanation of some aspect of the natural world, incorporating facts, laws, inferences and well-tested hypotheses. It is not a guess or speculation. Where and how can Kinetic Particle Theory be applied? This theory can be used to explain o the behaviour of the 3 states of matter (solid, liquid, gas) in terms of their properties o the interconversion and energy changes between the 3 states. _________________________________________________________________________ 2.2.2 CLASSIFICATION OF MATTER Matter can be classified as solids, liquids or gases One way to determine the state of matter: sketch the lines to show the temperature range Solid Liquid Gas Temperature/⁰C Melting Boiling point point * Melting point: The temperature at which a solid begins to melt and become a liquid * Boiling point: The temperature at which a liquid begins to boil and become a gas _________________________________________________________________________ 15 2.2.2.1 Arrangement and Movement of Particles of Matter SOLID LIQUID GAS 3D model Particle Diagram Arrangement The particles of a solid are closely packed The particles of a liquid are loosely packed The particles of a gas are very far apart in an orderly pattern with very little in a disorderly manner, with slightly more from one another in a disorderly space between them. spaces between them than in a solid. manner. Movement Vibrate and rotate about their fixed Slide over one another Rapidly and freely in all directions positions Energy level Low Moderate High Property 1: Shape Definite shape as the particles cannot No definite shape, but takes the shape of No definite shape, and takes the shape move about freely the container as particles are able to move of the container as particles are able to about move about Property 2: Solids cannot be compressed as Liquids cannot be compressed as particles Gases can be compressed as there are Compressibility particles are closely packed and there is are closely packed and there is little space large spaces between particles, hence, little/ almost no space between between particles. Thus particles cannot be particles can be pushed closer together. particles. Thus particles cannot be pushed closer together. pushed closer together. 16  2.2.2.2 Using KPT to explain behaviour of substances at different states 1. Compressibility of gases Study the diagrams below which shows a gas being compressed in a syringe. Explain why gases can be compressed using the KPT. Particles of a gas are far apart with lots of empty space between them. Hence, when pressure is ………………………………………………………………………………………………………………………………………………………….. applied, they can be pushed closer together and hence the volume of the gas decreases. ………………………………………………………………………………………………………………………………………………………….. 2. Comparing densities of substances at different states Given that density = , use the Kinetic Particle Theory to explain why solids have a much higher density than a gas. Particles in a solid are closely packed together while particles in a gas are far apart. As such, comparing the same volume, the number of particles in a solid is higher than a gas, causing the ………………………………………………………………………………………………………………………………………………………….. mass of a solid to be higher leading to a higher density in solids. ………………………………………………………………………………………………………………………………………………………….. Alt answer: Particles in a solid are closely packed together while particles in a gas are far apart. For the same mass (same number of particles), the volume occupied by a solid is larger compared to that of a gas. Thus, solids have a higher density. 17 3. Expansion and contraction of substances Expansion When matter is heated, the particles gain energy and move faster and further apart. Thus, volume increases. This causes the volume to increase. Contraction When matter is cooled, the particles lose energy and move slower and closer together. Thus, volume decreases. Note: This causes the volume to decrease. The mass of the substance remains unchanged There is no change in the size and number of the particles Given that density = , explain how the density of a substance changes when it is heated. When a substance is heated, the particles gain kinetic energy and move faster and further apart, …………………………………………………………………………