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Section 2.1

Section 2-1Section 2.1 Units and Measurements

• Define SI base units for time, length, mass, and temperature.

mass: a measurement that reflects the amount of matter an object contains

• Explain how adding a prefix changes a unit.

• Compare the derived units for volume and density.

Comprehension Verbs

explaininterpretoutlinediscussdistinguishpredictrestatetranslatecomparedescribe

activities and products

draw pictures to show a particular event.Illustrate what you think the main idea was.Make a cartoon strip showing the sequence of events.Write and perform a play based on the story.Retell the story in your words.Paint a picture of some aspect you like.Write a summary report of an event.Prepare a flow chart to illustrate the sequence of events.Make a coloring book.

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Units of Measurement Article: 26, 48 Terms: 25 Mastering Concepts: 50 (52-57) Lab: 28 copy table: p. 26 (2-1) and (2-2) Practice Problems: 29 (1-3) Homework:Cornell Notes: 2.1Section Assessment: 30(4-9) Mastering Problems: 50 (72-74) 11 Stamps

Section 2-1Units• Système Internationale d'Unités (SI) is an

internationally agreed upon system of measurements.

• A base unit is a defined unit in a system of measurement that is based on an object or event in the physical world, and is independent of other units.

Section 2-1Units (cont.)

Section 2-1Units (cont.)

m/1G

1m/10dm

Section 2-1Units (cont.)

• The SI base unit of temperature is the kelvin (K).

• Zero kelvin is the point where there is virtually no particle motion or kinetic energy, also known as absolute zero.

• Two other temperature scales are Celsius and Fahrenheit.

Section 2-1Derived Units (cont.)

• Density is a derived unit, g/cm3, the amount of mass per unit volume.

• The density equation is density = mass/volume.

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Mastering Concepts:

50(52-57)

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52. Why must a measurement include both a number and a unit? (2.1)• The number gives you the quantitative value, and

the unit indicates what was measured.53. Explain why scientists, in particular, need standard units of measurement. (2.1)• Scientists from different countries have different

languages and cultures but must be able to share and compare data.

Mastering Concepts

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54. What role do prefixes play in the metric system? (2.1)• Prefixes give the magnitude of the measurement.55. How many meters are there in one kilometer? In one decimeter? (2.1)• 1000; 0.156. What is the relationship between the SI unit for volume and the SI unit for length? (2.1)• The SI unit for volume is the cubic meter, m3, which is

equal to three SI measurements of length multiplied together.

Section 2-1Derived Units (cont.)

• A more convenient measure is the liter

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57. Explain how temperatures on the Celsius and Kelvin scales are related. (2.1)

• The sizes of the units are equal; °C + 273 = K.

Displacement Volume• It's the way to figure out the

volume of an irregular object. The volume is the amount of water that has been displace after putting in the object.

• Displace: how water level changes after adding an object

• The difference of initial and Final volume

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Volume Displacement• It's the way to figure out the

volume of an irregular object.

• The volume is the amount of water that has been displace after putting in the object.

• Displace: how water level changes after adding an object

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Density involves

• 2 quantities – Grams (mass)– Cubic centimeter (volume)

• one relationship – Grams/cm3

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Practicing Problems

29(1-3)

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page 29 Practice Problems

1. A piece of metal with a mass of 147 g is placed in a 50-mL graduated cylinder. The water level rises from 20 mL to 41 mL. What is the density of the metal?Density = mass/volume

Volume = 41 mL – 20mL = 21 mL

Density = 147g/21mL = 7.0g/mL

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p.29 (2)

2. What is the volume of a sample that has a mass of 20 g and a density of 4 g/mL?

Volume = mass/density

v o l u m e = density 20 g/4 g / m L =5 m L

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3. A metal cube has a mass of 20 g and a volume of 5 cm3. Is the cube made of pure aluminum? Explain your answer.

the density of the cube = mass/volume

= 20g/5cm3 = 4 g/cm3.

No; the density of aluminum is 2.7 g/cm3

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Mastering Problems: 50 (72)

Mastering Problems Density (2.1) Level 172. A 5-mL sample of water has a mass of 5 g. What is the density of water?

Density= mass/ volume = 5 g/5mL = 1g/mL