Mahopac Central School District Curriculum Introduction to Science 8

Transcription

1 Introduction to Science 8 A. The goal of science is to understand the natural world 1. As you make new observations and test new explanations your view of the natural world may change again and again 2. Science is self-correcting a. to understand science is to understand that what you know changes as you learn more about the world 3. Building knowledge in science is characterized by: observing (senses), explaining (hypothesis), testing explanations (experiments), analyzing results (conclusions), and critical review (peer evaluation) B. Observing something scientifically means using one or more of the senses to explain something carefully 1. You have five basic senses: sight, hearing, touch, taste, smell 2. A checklist for making good observations would include: a. color b. size c. shape d. taste e. smell f. sounds g. texture h.actions (what s it doing?) i. mass j. length k. volume l. time or rate of change m. density n. location C. Since human senses are not all that accurate, science turns to the use of instruments to make measurements 1. Instrument any device used to extend the human senses 2. Measurement a means of expressing an observation with great precision or accuracy a. most measurements involve the use of a number and a unit 3. Microscope a device that uses visible light to magnify objects a. always carry a microscope with both hands b. do NOT touch the lenses c. raise the eyepiece as high as it will go before placing a slide on the stage d. start with the lowest power use the coarse adjustment knob until the slide begins to come into focus then switch to the fine adjustment knob e. to use the high power lens, first focus under low power and then move the high power lens into place 4. Ruler/Meter Stick an instrument used to measure length or find volume of regular solids a. place the zero end of the ruler or meter stick next to one end of the object you are measuring b. find the other end of the object and read the number next to it on the ruler/meter stick 5. Graduated Cylinder an instrument used to measure volume of fluids a. volume the amount of space an object or substance takes up b. add the fluid to the graduated cylinder an place on a level surface c. move so that your eyes are level with the surface of the fluid d. read the level of the fluid at the bottom of the meniscus the downward curved surface of the fluid 6. Triple Beam Balance an instrument to determine mass a. mass the amount of matter in an object b. zero out the balance c. place the object on the pan of the balance and move the 100g slider to the right until the arm drops

2 d. move the 100g slider to the left one notch and leave it there e. repeat the procedure with the 10g slider f. move the 1g slider over until the arm balances read it to the nearest tenth g. add all the numbers from the three beams h. a spring scale can be used to determine approximate mass, too 7. Thermometer an instrument used to determine temperature a. temperature a measure of how quickly molecules vibrate b. place the thermometer in the middle of the substance you are measuring c. wait a bit for the reading to stabilize read to the nearest whole number 8. Stopwatch a device used to record the passage of time a. time your sense of one event happening after another b. zero out the display use the left hand button c. right hand button starts the display d. right hand button stops the display as well e. read and round to the nearest tenth D. Observations lead to questions 1. Usually you are looking at why something happens how does one thing or action influence another thing or action 2. A tentative, testable explanation of the observed relationship between factors is called a hypothesis a. a hypothesis is a scientists first try at explaining something b. a hypothesis must have three parts: 1) if statement (the condition) 2) then statement (the predicted results) 3) because statement (the explanation for the results) 3. When a hypothesis is continually supported by evidence it become a theory 4. When a theory is continually supported by evidence it becomes a law a. a law is an idea or concept that is almost equal to a fact E. Sharing ideas and findings is a major component of science 1. Peer review allows for an exchange of ideas 2. If a scientist discovers an error in the work of another, flawed conclusions may be prevented F. Designing Experiments 1. The purpose of an experiment is to answer a question or test a possible answer to a question (Identify and state the problem) 2. There are about seven steps to follow in experimental design: a. state a hypothesis a possible solution to the problem or a possible answer to a question about the problem b. identify the variables 1) a variable is anything than can affect the outcome of the experiment 2) one of the variables in an experiment is the factor you are testing 3) as much as possible, you want to control even the variables you are NOT testing in other words, test one variable at a time 4) a dependant variable is the one that was changed (affected) by the action of the independent variable in other words, the response 5) an independent variable the condition that is controlled by the scientist c. develop a procedure for performing the experiment 1) what steps will you take that will allow you to vary the factor you are testing while keeping all others constant?

3 2) A control setup same as the experimental setup except it does not contain the variable being tested d. gather data 1) run the experiment and record the results measurements should be taken e. analyze the results study and think about what you found out 1) graphs, charts, data tables, etc. are used to make the information you gathered more interesting and easy to analyze f. draw conclusions 1) was the hypothesis justified by the results of the experiment? 2) an inference a name given to the conclusion based on observations 3) a prediction an inference about what will happen in the future g. share results with peers called peer review or simply, communication G. Properties of Matter 1. Mass the amount of matter in an object a. it is determined with a triple beam balance, electronic balance, or spring scale b. the basic unit of mass is the gram c. weight changes with a change of position, mass doesn t 2. Volume the amount of space an object or substance takes up a. it is determined with: a mathematical formula, a graduated cylinder, or by water displacement the basic unit of volume is the cubic centimeter for solids and the milliliter for fluids b. a cube = sidexsidexside, a bar lengthxwidthxheight, a sphere=4/3πr3 c. irregular solids use water displacement: 1) add water to a graduated cylinder to a predetermined level 2) record this level 3) insert object into graduated cylinder 4) record the new water level 5) get the difference in water levels from the beginning to the end d. generally, as the temperature of a substance increases, it expands, and its volume increases 3. Density the concentration of matter in an object how tightly matter is packed in an object mass per unit volume a. the basic unit of density is the gram per cubic centimeter for regular solids, grams per milliliter for irregular solids or fluids b. density = mass divided by volume c. size, shape or amount have no effect on the density of a single, uniform material d. all density values are a comparison to liquid waters value of 1.0g/cc e. if a substance floats in water it s density is less than 1.0 f. if a substance sinks in water it s density is greater an 1.0 g. if a substance neither sinks nor floats when placed in water it has the same density as the water h. to calculate the density of a liquid or a powder: 1) mass a container 2) add the liquid to the container 3) mass the two together 4) subtract the mass of the empty container from the total together 5) this tells you the mass of the liquid

4 6) pour the liquid into a graduated cylinder 7) this tells you the volume of the liquid 8) use the formula D=M/V 4. Length the distance between two points a. the basic unit is the meter b. 1/100 th of a meter is a centimeter, 1/1000 th of a meter is a millimeter, and 100 meters is a kilometer 5. Magnetism it is the force of repulsion or attraction associated with matter a. the law of poles says: like poles repel and unlike poles attract b. it is the spinning of electrons on their axis as they orbit the nucleus that generates magnetism 1) the area over which this magnetism acts is called a magnetic field 6. Conductivity the ability of matter to permit the transfer of heat or electrical energy through it a. most metals and salt-water solutions will conduct electricity All measurements, even those made with the best instruments, contain error This error is expressed as a % from the accepted value % of error = difference from the accepted value accepted value x 100 H. Graphing a way to display large amounts of data in a way that is easy to understand 1. There are three types of graphs: line graphs, bar graphs, and pie graphs 2. Line Graphs - used to compare things when the data represents a continuous process a. a graph tries to answer the question: does the changing of the independent (scientist controlled) variable affect the dependant (responding) variable? b. a title tells the reader what data the graph is displaying c. the axes: X-axis (horizontal) displays the independent variable while the Y- axis (vertical) displays the dependant variable 1) if some unit of time is a variable, it always goes on the X-axis d. both axes need to be labeled with the appropriate units e. scaling means numbering the grid so that the data can be displayed 1) the scale = range of data number of boxes 2) if this doesn t produce a whole number round up to the nearest whole number f. the scales of the X and Y axes need not be the same g. plotting placing the points on the graph that represent the information from the data table h. interpolating following the same pattern the points present i. best fit draw a line that comes as close to as many of the points as possible j. slope how much the X-axis variable changes as compared to how much the Y-axis variable has changed 1) the formula for slope = Y/ X where Y= Y final value minus Y initial value and X = X final value minus X initial value k. when some unit of time is the independent variable, the steeper the slope of the graphed data, the greater the rate of change 3. Bar Graphs used to compare things when the X-axis does not represent a continuos scale

5 a. the X-axis is a set of distinct categories that represents the changing of some variable 4. Pie Graphs used to compare things by assigning them some portion of a full circle a. the portions are some % of the full 100% b. the larger the wedge, the greater the proportion to the whole I. Relationships how a change in the independent variable causes the dependent variable to change 1. Direct Relationship both variables change in the same direction 2. Indirect Relationship variables change in opposite directions J. Classification the grouping together of objects or events on the basis of what they have in common with each other K. Modeling the representation of an object or idea 1. it s not the real object or idea, just something used to represent it 2. many models are done to scale or true proportion L. Research to draw upon the knowledge gathered by others M. Laboratory Safety 1. Plan your work a. read all instructions before starting b. study the steps of the procedure c. clear your work area of items that won t be used 2. Follow the steps in order a. changing the order could cause unexpected reactions b. changing the order could ruin the results of the experiment 3. Never work alone a. in an accident you ll need someone to help you 4. Never eat or drink in the laboratory a. substance you are working with can contaminate your food or drink b. your food or drink could contaminate the substances you are working with 5. Keep your body safe a. tie back long hair b. roll up long sleeves c. wear gloves/aprons when working with messy or dangerous materials d. wear safety goggles/glasses 6. Be careful with electricity a. check for loose plugs or worn cords b. keep your hands dry c. make sure cords are in a safe place where you can t trip over them d. don t pull out a plug by its cord 7. Use laboratory equipment appropriately a. return all materials to their proper places b. clean up spills, puddles, etc. c. notify the teacher immediately if an accident occurs N. Microscope Work use the various packets with the microscopes to check proficiency