1 / 32

Measurement Notes

Measurement Notes. Chapter 2. Scientist use the metric system—a standard measurement system based on the #10. The meter is the basic unit. millimeter = mm King Kilo (100 centi ) centimeter = cm Henry Hecto (10 deci ) decimeter = dm Died Deca

myrna
Download Presentation

Measurement Notes

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Measurement Notes Chapter 2

  2. Scientist use the metric system—a standard measurement system based on the #10. The meter is the basic unit. millimeter = mm King Kilo (100 centi) centimeter = cm Henry Hecto (10 deci) decimeter = dm Died Deca meter = m While Whole (1,000 kilo) kilometer = km Drinking Deci 10 mm = 1 cm Chocolate Centi 10 cm = 1 dm Milk Milli 100 cm = 1m 1000 m = 1 km Length

  3. Kilogram Prototype C. 12 milligrams or 12 kilograms D. 4 kilograms or 4500 grams A. 1 kilogram or 1500 grams B. 1200 milligrams or 1 gram kg Metric Units cg mg g Mass refers to the amount of matter in an object. The base unit of mass in the metric system in the gram and is represented by g. Standard: 1 kilogram is equal to the mass of the International Prototype Kilogram (IPK), a platinum-iridium cylinder kept by the BIPM at Sèvres, France. Metric Units 1 Kilogram (kg) = 1000 Grams (g) 1 Gram (g) = 1000 Milligrams (mg) Which is larger?

  4. Balance Rules In order to protect the balances and ensure accurate results, a number of rules should be followed: • Always check that the balance is level and zeroed before using it. • Do not weigh hot or cold objects. • Clean up any spills around the balance immediately.

  5. Once you have balanced the scale, you add up the amounts on each beam to find the total mass. What would be the mass of the object measured in the picture? _______ + ______ + _______ = ________ g Measuring Mass We will be using triple-beam balances to find the mass of various objects. The objects are placed on the scale and then you move the weights on the beams until you get the lines on the right-side of the scale to match up. Top Image: http://www.southwestscales.com/Ohaus_Triple_Beam_750-SO.jpgBottom Image: http://www.regentsprep.org/Regents/biology/units/laboratory/graphics/triplebeambalance.jpg

  6. 1st – Place the film canister on the scale. 2nd – Slide the large weight to the right until the arm drops below the line. Move the rider back one groove. Make sure it “locks” into place. 3rd – Repeat this process with the top weight. When the arm moves below the line, back it up one groove. 4th – Slide the small weight on the front beam until the lines match up. Measuring Mass – Triple-Beam Balance 5th – Add the amounts on each beam to find the total mass to the nearest tenth of a gram.

  7. Check to see that the balance scale is at zero

  8. Volume is the amount of space a substance occupies The liter (L) is the base unit Tools: metric ruler is used to measure regular solids v=l x w x h (cm3) or a graduated cylinder for liquids and irregular solids (mL) Meniscus- the curved surface of liquid resulting from surface tension Volume

  9. Graduated Cylinders The glass cylinder has etched marks to indicate volumes, a pouring lip, and quite often, a plastic bumper to prevent breakage.

  10. Reading the Meniscus Always read volume from the bottom of the meniscus. The meniscus is the curved surface of a liquid in a narrow cylindrical container.

  11. Try to avoid parallax errors. Parallaxerrors arise when a meniscus or needle is viewed from an angle rather than from straight-on at eye level. Correct: Viewing the meniscusat eye level Incorrect: viewing the meniscusfrom an angle

  12. Significant Figures • Significant figures in measurement include the all certain digits and one uncertain digit. • Significant figures communicate how precise measurements are. • Certain digits are determined from the calibration marks on the cylinder. • The uncertain digit (the last digit of the reading) is estimated.

  13. Use the graduations to find all certain digits There are two unlabeled graduations below the meniscus, and each graduation represents 1 mL, so the certain digits of the reading are… 52 mL.

  14. Estimate the uncertain digit and take a reading The meniscus is about eight tenths of the way to the next graduation, so the final digit in the reading is 0.8 mL 52.8 mL. The volume in the graduated cylinder is

  15. Self Test Examine the meniscus below and determine the volume of liquid contained in the graduated cylinder. The cylinder contains: 7 6 0 _ _ . _ mL

  16. Irregular Volume A solid with an irregular volume will be measured using the displacement method • Measure and record an amount of water • Drop the irregular object in the cylinder • Read the cylinder again and record the amount • Subtract the two measurements and the result is the volume of the irregular object in ml

  17. The Thermometer • Determine the temperature by reading the scale on the thermometer at eye level. • Read the temperature by using all certain digits and one uncertain digit. • Certain digits are determined from the calibration marks on the thermometer. • The uncertain digit (the last digit of the reading) is estimated. • On most thermometers encountered in a general chemistry lab, the tenths place is the uncertain digit.

  18. Do not allow the tip to touch the walls or the bottom of the flask. If the thermometer bulb touches the flask, the temperature of the glass will be measured instead of the temperature of the solution. Readings may be incorrect, particularly if the flask is on a hotplate or in an ice bath.

  19. Reading the Thermometer Determine the readings as shown below on Celsius thermometers: 8 7 4 3 5 0 _ _ . _ C _ _ . _ C

  20. Mass • Mass is the amount of matter in an object • It is determined by using a balance • The unit for mass is grams.

  21. 1 pound = 453.6 grams 1 ounce of gold = 28,349.5 milligrams 100 kilogram = 220 pounds English vs. Metric Units Which is larger? 1. 1 Pound or 100 Grams 2. 1 Kilogram or 1 Pound 3. 1 Ounce or 1000 Milligrams

  22. Density • The measure of how much mass is contained in a given volume.

  23. The formula of density is: Density = Mass / Volume

  24. Comparing Densities - Inferring: Which item has the greater density? • The bowling ball • Since the bowling bowl has a greater mass, it has a greater density, even though both balls have the same volume

  25. Why is density expressed as a combination of two different units? • Because density is actually made up of two other measurements – mass and volume – an objects density is expressed as a combination of two units.

  26. Two Common Units For Density • Grams per cubic centimeter (g/cm³) • Grams per milliliter (g/mL)

  27. Math Practice:What is the density of a wood block with a volume of 125 cm³ and a mass of 57 g? Density = mass / volume Density = 57 g / 125 cm³ Density = 0.46 g/ cm³

  28. Math Practice:What is the density of a liquid with a mass of 45 g and a volume of 48 mL? Density = mass / volume Density = 45 g / 48 mL Density = 0.94 g/mL

  29. The density of a substance is the ______for all samples of that substance. • Same

  30. An object will float if it is _____ _____ than a surrounding liquid. • Less dense

  31. If the bar of gold has a density that is greater than or less than 19.3 g/cm³, then the sample is not pure gold. Applying Concepts: How could you use density to determine whether a bar of metal is pure gold?

  32.  Will an object with a density of 0.7 g/cm³ float or sink in water? • An object that has a density of 0.7 g/cm³ will float in water (1 g/cm³) because it is less dense than water

More Related