Do Now: Accuracy & Precision

1. Do Now: Accuracy & Precision Draw two bullseyes. On one, show three darts that are accurate. On the other, show three darts that are precise.

2. YWBAT • Explain why metric units are easy to use. • Identify the temperature units scientists usually use. • Calculate the density of a substance.

3. Measuring Length • What units can you use to report length?

4. Measuring Length • What units can you use to report length? • Inches • Feet • Meters • Miles

5. Metric Units • The standards of measurement used in science are those of the metric system • All metric units are based on multiples of 10. • This makes it easy to convert between units

6. SI Units • The metric system was established in France in 1795 • The International System of Units is a revised version of the metric system. It is abbreviated SI after the French name, Le Système International d’Unités. • The SI was adopted by international agreement in 1960.

7. SI Units • There are 7 base SI units • From these base units, all other SI units of measurement can be derived. • Derived units are used for measurements such as volume, density, and pressure.

8. Units of Length • In SI, the basic unit of length is the meter (m). • All measurements of length can be expressed in meters. • For very large and very small lengths, however it may be more convenient to use a unit of length that has a prefix.

9. Unit Prefixes

10. Units of Length • The SI unit for length is a meter (m). • The prefix milli- means 1/1000 • 1 millimeter = 1/1000 of a meter = 0.001m • 1 mm = 0.001m • The prefix kilo means 1000 times larger • 1 kilometer = 1000 meters • 1 km = 1000m

11. Funny Forms of 1

12. Units of Volume • Volume – space occupied by matter • For a rectangular solid, V = L x W x H • The SI unit of volume is a cubic meter (m3). • A more convenient unit of volume for everyday use is the liter, a non-SI unit.

13. Units of Volume • A more convenient unit of volume for everyday use is the liter. This is a non-SI unit. • A liter (L) is the volume of a cube that that is 10 centimeters along each edge. 10cm x 10cm x 10cm = 1000 cm3 = 1L

14. Units of Volume • A smaller non-SI unit of volume is the milliliter (mL). Question? How many cm3 are equivalent to 1 mL?

15. Units of Volume • A smaller non-SI unit of volume is the milliliter (mL). Question? How many cm3 are equivalent to 1 mL? 1 cm3 = 1 mL The units mL and cm3 are used interchangeably

16. Measuring Volume

17. Measuring Volume

18. Measuring Volume • Put on goggles & apron. • Get the following equipment for each group. • 100 mL Graduated cylinder • 100 mL Beaker • Fill beaker with ~ 70 mL water. • Pour water into graduated cylinder. • Read the volume on the graduated cylinder. Be sure to: • get your eye level at the interface. • read the bottom of the meniscus.

19. Units of Mass • Mass – a measure of the quantity of matter. • The SI unit of mass is the kilogram (kg). • 1 kg = the mass of 1 L of liquid water at 4°C • A more convenient unit of volume for everyday use is the gram (g) • 1 kg = 1000 grams.

20. Measuring Mass

21. Weight • Zero your balance • Determine the tare weight of your beaker • Add ~70mL water to your beaker • Weigh the beaker containing the water • Calculate the weight of the water.

22. Weight • Weight is a force that measures the pull on a given mass by gravity. • The weight of an object can change with its location

23. Weight How much would you weigh on the Moon? Divide your weight on Earth by 6.

24. Density • Density is the ratio of the mass of an object to its volume. • The relationship between an objects mass and volume tells you whether it will float or sink. • Density is an intensive property.

25. 10 g 10 g 10 g 10 g 19 cm3 10 cm3 3.7 cm3 0.88 cm3 0.53 g/cm3 1.0 g/cm3 2.7 g/cm3 11.4 g/cm3 Density • The SI unit of density is kilograms per cubic meter (kg/m3). Increasing density (mass per unit volume)

26. Density • Differences in densities cause liquids to separate into layers. • As shown below, corn oil floats on top of water because it is less dense than water. Corn oil Water Corn syrup

28. Practice A copper penny has a mass of 3.1g and a volume of 0.35 cm3. what is the density of copper?

29. 31 g Density = = 8.8571 g/cm3 = 8.9 g/cm3 0.35 cm3 Practice A copper penny has a mass of 3.1g and a volume of 0.35 cm3. what is the density of copper?

30. Density • The volume of most substances increase as the temperature increases, while the mass remains the same. • The density of a substance generally decrease as its temperature increases. • Water is an important exception.

31. Temperature Temperature is a measure of how hot or cold an object is. • An object’s temperature determines the direction of heat transfer. • When two objects at different temperature are in contact, heat moves from the object at the higher temperature to the object at the lower temperature.

32. Temperature • The SI unit for temperature is the Kelvin, named after Lord Kelvin, a Scottish physicist. • On the Kelvin scale, the freezing point of water is 273.15 Kelvin (K), and the boiling point is 373.15 K. * Note that with the Kelvin scale, the degree sign is not used.

33. Temperature • Another common unit used to measure temperature is the Celsius scale. • On the Celsius scale, the freezing point of water is 0°C, and the boiling point is 100°C.

34. Comparing the °C and K Temperature Scales * Note - The zero point on the Kelvin scale, 0 K, or absolute 0, is equal to -273.15°C

35. Comparing the °C and K Temperature Scales • One degree on the Celsius scale is equivalent to one Kelvin on the Kelvin scale. • To convert between the temperature scales,

36. Practice Normal human body temperature is 37°C. What is this temperature in kelvins?

37. Practice Normal human body temperature is 37°C. What is this temperature in kelvins? 310 K

38. Practice A student is performing an experiment and measures the temperature of water to be 350 K. What is the temperature of the water in ºC?

39. Practice A student is performing an experiment and measures the temperature of water to be 350 K. What is the temperature of the water in ºC? 77ºC