Dr. LAILA AL-HARBI

Measurement SI units Mass and weight Volume Temperature scales

Chapter 1The study of change

Dr. LAILA AL-HARBI

By the end of this chapter you should: Know the 7 SI basic units and their prefixes. Be able to convert from one unit to other. Know to derive units from the 7 SI basic units. Common units (L & mL) Know the temperature Scales

Objectives

Dr. LAILA AL-HARBI

Chemistry is the study of matter and the changes it undergoes

There are three states of matter

Introduction

solidliquid

gas

Dr. LAILA AL-HARBI

1.7 Measurement and UnitsThe International System of units (SI Units)

used for commerce and science around the world

5

The SI unit of mass is

(a) The pound

(b) The gram

(c) The kilogram

(d) The mole

Examples

The Kg is the SI unit of

(a) length

(b) mass

(c) temperature

(d) current

Dr. LAILA AL-HARBI

1m

Dr. LAILA AL-HARBI

A) use numerical line االعداد خطB) use transfer factor التحويل معامل

أو مضاعفتها و األساسية الوحدة من للتحويلأو االعداد خط استخدام يمكننا المشتقات

الطريفين ) بضرب التحويل معامل استخدامالوسطين ( .في

To transfer between perifexs

Dr. LAILA AL-HARBI

أو مضاعفتها و االساسية الوحده من للتحويلاستخدام أو االعداد خط استخدام يمكننا المشتقات ) ( و الوسطين في الطريفين بضرب التحويل معاملالطريقتين أن كما الطريقتيين بين تخلطي ال لكنبطريقة بنفس استخدامها تم اذا النتيجة نفس يعطوا

صحيحة.

TGMKSIdcmµnp

103 103103103 103 103 101010 103

1012109

106

103

1012

109106

103102 10

التحويل معامل التحويل معامل

الوحده تزيد االتجاه بهذا

صغيرة وحدة كبيرة وحدة

نقسم كبير الى صغير من من , ÷للتحويل للتحويلنضرب صغير الى × كبير

Dr. LAILA AL-HARBI

I. Convert 134 pm to m?II. How many meters are in 134 pm?

نقسم كبير الى صغير من ÷ للتحويل

1 pm = 1×10-12 m134 pm = ?? m

االعداد خط باستخدام الحل

وسطين في طرفين الجدول باستخدام الحل

134 ×1×10-12 m = 1.34×10-10 m

Examples The SI prefixes giga and micro represent, respectively: 

A. 10-9 and 10-6. B. 106 and 10-3. C. 103 and 10-3. D. 109 and 10-6.

The SI unit of mass is

(a). The pound

(b). The gram

(c). The kilogram

(d). The mole.

Dr. LAILA AL-HARBI

Dr. LAILA AL-HARBI

How many microseconds are in a second?(a). 1 x 10-1

(b). 1 x 10-6

(c). 1 x 10-15

(d). 1 x 10 6

Explanation: Since the prefix micro means 1 x 10-6, there will be 1 x 10 + 6 microseconds in one second.

1 µs= 1 x 10 -6 sx µs = 1 s

s µs

1 10 6 x 1 x 10 6 µs

Dr. LAILA AL-HARBI

Which of the following is the smallest distance? (a) 21 m → 21m (b) 2.1 x 102 cm → 2.1m (c) 21 mm → 0.021 m (d) 2.1 x 104 pm → 2.1 x 10-8 m

Put all of them in the same unit

Explanation: Even though 2.1 x 104 is the largest number in this question, the units of pm (picometers) are the smallest units here, making it the smallest distance.

Example

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A) 6.0 km is how many micrometers? 

Solution 1

1 km = 103 m

6 km = x = 6 × 103 m

1µm = 1× 10-6 m

x = 6 × 103 m

x = 6 × 109µm Explanation: convert first to meter then from meter to micro

( two steps solution )

km µm

×6 109 6 × 109

Dr. LAILA AL-HARBI

Example The diameter of an atom is

approximately 1 10-7 mm. What is this diameter when expressed in nanometers? 

A. 1 10-18 nm B. 1 10-15 nm C. 1 10-9 nm D. 1 10-1 nm

= 1× 10-7 × 1 × 106 = 1 × 10-1 nm = 0.1 nm

Example

Which of these quantities represents the largest mass? 

A. 2.0 102 mg B. 0.0010 kg C. 1.0 105 g D. 2.0 102 cg Put all of them in the same

unit A) 0.2 gB)1 gC) 0.1 gD) 2 g

Dr. LAILA AL-HARBI

are defined in terms of the seven base quantities via a system of quantity equations.

The SI derived units for these derived quantities are obtained from these equations and the seven SI base units. For example

Area = width x length Unit of width = m Unit of length = m Unit of Area = m× m = m2

SI derived units

Treat units like numbers

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Volume –

Volume = width × length × heights = m × m × m = m3

SI derived unit for volume is cubic meter (m3)

Common unit of volume is liter (L) and milliliter (ml)

The relation ship between liter (L) and ml (1L= 1000mL)

The relation ship between liter (L) and metric system

1 L = 1 dm3

The relation ship between milliliter (ml) and metric system

1 mL = 1 cm3

1 cm3 = (1 x 10-2 m)3 = 1 x 10-6 m3

1 dm3 = (1 x 10-1 m)3 = 1 x 10-3 m3

Dr. LAILA AL-HARBI

Example (1)

Example (2)

How many liters are in 25 dm3 ?

Science 1L = 1 dm3

25 dm3 = 25L

How many milliliters are in 32 cm3 ?

Science 1mL = 1 cm3

32 cm3 = 32 mL

Example (3)

How many liters are in 250 cm3 ?

Science 1L = 1 dm3

and 1mL = 1 cm3

250 cm3 = 250 mL L → mL 250/1000 = 0.25 L

Dr. LAILA AL-HARBI

How many cubic centimeters are there in exactly one cubic meter? 

A. 1 10-6 cm3

B. 1 10-3 cm3

C. 1 10-2 cm3

D. 1 106 cm3

Solution (1m )3 = (cm )3

1m3 = (1 102)3 cm 3

1m3 = 1 106 cm3

Examples

The diameter of an atom is approximately 1 10-7 mm. What is this diameter when expressed in nanometers? 

A. 1 10-18 nm B. 1 10-15 nm C. 1 10-9 nm D. 1 10-1 nm

Dr. LAILA AL-HARBI

Mass is the measure of the amount of matter in an object.

SI unit of mass is the kilogram (kg)

1 kg = 1000 g = 1 x 103 g

Weight is the measurement of the pull of gravity on an object.

The Mass of an object doesn't change when an object's location changes. Weight, on the other hand does change with location.

Chemist are interested primarily in mass

weight = c x mass

Mass and Weight

The weight of man on earth is 50 pounds.is 8.25 pounds on moon

Dr. LAILA AL-HARBI

Density is defined as the amount of matter in a given amount of space.

SI derived unit for density is kg/m3

common units of density are g/mL , g/L

Density decrease with temperature (g/ml )g/cm3 for liquid and solids g/L = 0.001g/ml for gases

Because density of gases are very low

Density

The density of copper is 8.94 g/cm3.

density = mass

volume

21

Questions in Density

Given

m & V

? d

d = m/V

Given

m & d

? V

V = m /d

Given

V & d

? m

m = d x V

Dr. LAILA AL-HARBI

Example 1.1

A piece of Gold metal has a volume of 15.6 cm3, with a mass of 301 g What is its density?

A piece of platinum metal with a density of 21.5 g/cm3 has a volume of 4.49 cm3. What is its mass?

d = mV

m = d x V

= 21.5 g/cm3 x 4.49 cm3 = 96.5 g

d = mV

301 g/ 15.6 cm3 = 19.3 g/ cm3

Dr. LAILA AL-HARBI

Example 1.2

The density of mercury is 13.6 g/mL has a volume of 5.50 mL. What is its mass?

The density of sulfuric acid is 1.41 g/mL has a volume of 242 mL. What is its mass?

d = mV

m = d x V

= 1.41 g/mL x 242 mL = 341.22 g

d = mV

m = d x V

= 13.6 g/mL x 5.50 mL= 74.8 g

Dr. LAILA AL-HARBI

Fahrenheit °F: °F = [ (9/5) × °C] + 32 Celsius °C: °C = (5/9) (°F - 32) Kelvin K: K = °C + 273.15

Temperature Scales

25

Temperature Units Conversion1. Degrees Celsius 0C: Scale 0 → 100 Thus:

100 divisions or 100 degrees2. Kelvin K: Scale 273 → 373Thus: 100 divisions or 100 degrees1K = 1 C3. Degrees Fahrenheit 0F : Scale from 32→ 212 Thus: 180 divisions or 180 degreesThus: the size of degree in 0F scale is only 100/180

or5/9 of a degree on the 0C scale 10F = (5/9) 10C

Dr. LAILA AL-HARBI

Convert 224 0C to degrees Fahrenheit? °F = (9 0F /5 0C) × °C + 32 [°F = (9 0F /5 0C) × 224 °C] + 32 0C = 435 0F

Convert -452 0F to degrees Celsius. °C = (5 0C /9 0F) (°F - 32 0F) °C = (5 0C /9 0F) (-452 °F - 32 0F) = -269 0C

Convert -38.9 0C to degrees Kelvin.. ° K = [-38.9 °C + 273.15 °C ] × 1 K/ 1 0C = 234.3 K

Example 1.3

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Ammonia boils at -33.4C. What temperature is this in F? 

A. -60.1F B. -92.1F C. -28.1F D. +13.5F

F = (9 0F /5 0C) × °C + 32[°F = (9 0F /5 0C) × -33.4 °C] + 32 0C = - 28.1 0F