Chap 1 Section 2- Describing Matter

Characteristics of matter The SI system – units of measurementConversion of the units and calculationIdentify physical and chemical properties.

Matter• Cloud• Apple• Electron• Heat• Air• Trees• Atom

• Gravity• Student• Carbon dioxide• Fire• Molecule• Dream• Drop of water

Matter

All matter have physical properties. Matter has Volume, Mass and Density.Volume – the space the object occupies.Mass – the quantity of matter.Density – the ratio of mass to volume

How to measure and calculate?What is the units of these physical properties

Systems of UnitsSI System:SI System: The international system of The international system of units established by the International units established by the International Committee on Weights and Measures. Committee on Weights and Measures. Such units are based on strict Such units are based on strict definitions and are the only definitions and are the only officialofficial units for physical quantities.units for physical quantities.US Customary Units (USCU):US Customary Units (USCU): Older units Older units still in common use by the United still in common use by the United States, but definitions must be based States, but definitions must be based on SI units.on SI units.

SI (System International Unit )

Chapter 1

Seven Fundamental Units

Units for Chemistry

QuantityQuantity SI unitSI unit USCS unitUSCS unit

MassMass kilogram (kg)kilogram (kg) slug (slug)slug (slug)

VolumeVolume Cubic meter Cubic meter

( )( )Cubic footCubic foot

TemperatureTemperature Celsius ( )Celsius ( ) Fahrenheit Fahrenheit (F)(F)

Amount of Amount of substancesubstance

MoleMole Mole Mole

3mC

InIn ChemistryChemistry we use only a few fundamental we use only a few fundamental quantities: quantities: mass, volume, and mole etcmass, volume, and mole etc. An . An additional quantity, additional quantity, densitydensity is derived from some is derived from some of above units.of above units.

SI system

When working with numbers, be careful to distinguish between a quantity and its unit.

Quantity describes something that has magnitude, size, or amount.

Unit is a quantity adopted as a standard of measurement.

• Base units can be too large or too small for some measurements, so the base units may be modified by attaching prefixes.

Procedure for Converting Units

1. Write down quantity to be converted.

2. Define each unit in terms of desired unit.

3. For each definition, form two conversion factors, one being the reciprocal of the other.

4. Multiply the quantity to be converted by those factors that will cancel all but the desired units.

Example 1: Convert 12 in. to centimeters given that 1 in. = 2.54 cm.

Step 1: Write down Step 1: Write down quantity to be quantity to be converted.converted.

12 in.12 in.

Step 2. Define each Step 2. Define each unit in terms of unit in terms of desired unit.desired unit.

1 in. = 2.54 1 in. = 2.54 cmcm

Step 3. For each Step 3. For each definition, form two definition, form two conversion factors, one conversion factors, one being the reciprocal of being the reciprocal of the other.the other.

cm

in

54.2

1

in

cm

1

54.2

Example 1 (Cont.): Convert 12 in. to centimeters given that 1 in. = 2.54 cm.

From Step 3From Step 3. or

Wrong Wrong Choice!Choice!

Step 4. Multiply by those factors that Step 4. Multiply by those factors that will cancel all but the desired units. will cancel all but the desired units. Treat unit symbols algebraically.Treat unit symbols algebraically.

Correct Correct Answer!Answer!

cm

in

cm

inin

2

7.454.2

112

cmin

cmin 5.30

1

54.212

Practice problems

Let’s do some example problem together 1.Convert 2.53 mL to Liters2.Convert 1258 cm to meters3.Convert 15 g to kilograms

•Page 14 •# 1-3 work with your partner who is sitting next to you.

Properties of MatterPhysical Properties

• A physical property of a substance is a characteristic that does not involve a chemical change.

• Physical properties of a substance can be determined without changing the nature of a substance.

Properties of matterPhysical properties

• Physical properties describe a matter. One of properties is Density.

mL

gor

cm

g3V

mD

Concept Map of Density• Mass Volume• Units for volume of a regular solid• the amount of matter something has • Balance or scale• Water displacement • graduated cylinder• Gram ml ml• Units for volume of an irregular object • the amount of space something takes up• Units for volume of a liquid • Of an irregular object is measured by • L x W x H• Units for mass

Properties of Matter, continued

• The density of a substance is the same no mater what the size of the sample is.

Example

• Find the density of sulfuric acid if 15 cm3 has a mass of 27.6 g.

Unknown density of sulfuric acid data V = 15 cm3 M = 27.6 g D = M/V 27.6g / 15 cm3 = 1.84 g/cm3

Practice problems

• Find the density of a block of metal which is 16 mm long, 12 mm wide and 5 cm high. The mass of this block is 108960 mg.

• Find the mass in grams of a bar of silver 6 cm long, 10 cm wide and 4 cm high. Silver has a density of 10.5 g/cm3

• Find the volume of a container necessary to hold 200 g of mercury. The density of mercury is 13.55 g/cm3.

Properties of Matter, continued Chemical Properties

• A chemical property a property of matter that describes a substance’s ability to participate in chemical reactions.

• A chemical property of many substances is that they react with oxygen.

example: rusting

• Some substances break down into new substances when heated.