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Physical Science Ch. 1 Part II Physical Science Methods How Familiar Are You with Units of Measurement? 10 km is about how far in miles? A person who has a mass of 75 kg weighs about how much in pounds. About how much is a quart, and how many quarts are in a 2 liter bottle? 10 km = 6.2 miles 75 kg = 165 pounds 2 liters = 2.12 quarts • If a long-jumper goes 7.255 m, is that good or bad? • The speed limit says 104 km/hr. How fast is that? • The boy weighed 78 kg. What weight class will he wrestle? Standards A standard is an exact quantity used for comparison. There are 2 commonly used systems of measurement. The SI system (worldwide) and English units (primarily in the U.S.). How many cubits from one side of the room to the other? Why do you think the U.S. does not use the SI system as much as the rest of the world? What are some SI units which we see commonly used in the U.S.? SI System of Measurement The SI system is a base ten system of measurement. All units are either multiples of 10, or decimals. Prefixes added to root words will tell you what multiple a measurement is. For example........ Centi- = 1/100 or .01 1 meter = 100 cm Milli- = 1/1,000 or .001 1 meter = 1,000 mm Kilo- = 1,000X 1,000 meters = 1 km Time • Time is the interval between two events, and is the only measurement which uses the same units (seconds) for both SI and English measurements. Length Length is a measure of the distance between 2 points. The SI unit for length is the meter (m). • The lead in a mechanical pencil is usually measured in millimeters (mm), referring to it’s width. Mass Mass is a measure of the amount of matter in an object. The SI unit for mass is the kilogram (kg). Mass is measured using a balance (not a scale.). • The formula for mass is Mass = Density x Volume We'll use this formula later on. Also, 1 kg = 2.2 pounds A wood dowel, metal rod, and a candle all have different masses, even if they're the same size. Is mass the same as weight? Explain. Volume Volume is the amount of space occupied by an object (how big it is). For a regularly shaped object (square or rectangular) volume is measured in cm3. The formula is length x width x height. • What is the volume of the object shown below? • If you have an object that is not a perfect square or rectangle, how do you think you could find it's volume? • The best way to find the volume of an irregularly shaped object is through water displacement. Density Density is the amount of mass an object or material has, based on it's volume. For example, if I have 2 objects the exact same size, the one with more matter in it is denser. Like a bowling ball and a styrofoam ball. • Some examples of objects or materials where density is important: -a snowball -liquid mercury -humans floating and/or sinking -a lead sinker -warm and cold air The Dead Sea The formula for density is mass divided by volume. If mass is measured in grams and volume is measured in cm3, the mass/density would result in the label being g/ cm3. Water for example has a density of 1 g/ cm3. Derived Units Units which are a combination of other units are called derived units. Ex.: cm3 for volume, mi/hr for speed Temperature • Temperature is a measure of the average kinetic energy of the particles in a sample of matter. As you heat an object up, the particles move faster (higher kinetic energy), and the temperature increases. • The SI unit for temperature is the Kelvin. Although the celcius and fahrenheit scales are more commonly used. Absolute Zero • As the temperature of a material decreases, particle movement slows. If the temperature decreases to a point where particle movement stops completely, this is called absolute zero. (0 Kelvin) • Absolute zero is theoretical, in that it has never been achieved. Temperature Conversions • F = (C x 1.8) + 32 • C = (F - 32) x .55 • K = C + 273 • Ex.: If the temperature at the lake is 95 degree Fahrenheit, what is it in degrees Celsius. (95 – 32) x .55 = 34.65 degrees Celsius Practice Problems 1. Convert 14 degrees Fahrenheit to Celsius and to Kelvins. 2. A rock dropped into a beaker of water causes the water level to rise from 415 mL to 675 mL. What is the volume of the rock? 3. If the rock in problem #2 has a mass of 520 g, what is it’s density? 1. Convert room temperature (72 F) to: A. Celcius B. Kelvin 2. A brick has a height of 8 cm, width of 12 cm, and length of 20 cm. What is it’s volume? 3. If the brick in problem #2 has a mass of 3840 g, what is it’s density? 4. Will the brick float or sink in water? Explain why. 5. A beaker has 235 mL of water in it. When a flashlight battery is dropped in, the water level rises to 485 mL. What is the volume of the battery? 6. If the battery in problem #5 has a density 1.5 g/cm3, what is the mass of the battery? 1. Convert 450 cm to: A) Km B) mm 2. If the melting point of lead is 327 degrees Celsius, what is it in: A) degrees Fahrenheit B) Kelvins 3. An unknown metal has a volume of 5 cm3 and a mass of 13.5 g. Using the table on pg. 19, identify this metal. Graphing A graph is a visual display of information or data. Graphs often show patterns or relationships in the data, and may be used to predict future results. Types of Graphs There are 3 main types of graphs: 1. Line graph - shows trends or patterns over time, usually with larger numbers 2. Bar graph - compares smaller values which are usually counted 3. Circle (pie) graph - shows 1 fixed quantity broken down into parts (usually percentages) Line Graphs • Line graphs use an X axis (horizontal) and a Y axis (vertical) to plot data points, which are then connected with either a straight or curving line. • The data measured on the X axis is the independent variable, and the Y axis shows the dependent variable. The graph below shows how long students had to wait while registering for school this past month. • What does the graph show you? • Hypothesize as to why Monday and Friday had the longest wait times. Bar Graph • A bar graph is very similar to a line graph, just with smaller numbers. • Also, a bar graph shows information, but may or may not show any patterns or trends. For example........ Circle Graphs • Circle graphs are best at showing percentages. • Examples of information you may see on a circle graph include...... Opinion Polls Do you favor or oppose Initiative and Referendum? Election results 2004 Presidential Election 1% 3% 3% Bush 47% Kerry Nader Sharpton 46% Other Financial Information Dollar Breakdown of Expenses in the Pleasant Hill School District Salaries-41 cents Facilities-29 cents Textbooks-16 cents Supplies-9 cents Other-5 cents