Describing Matter 1.2

Objective/Warm-Up The students will be able to use the metric system to solve conversion problems and solve density problems. What do you know about the metric system? Why is it useful? What do you know about the metric system? Why is it useful?

Chemistry investigates the nature of matter Matter – anything that has mass and takes up space Matter – anything that has mass and takes up space Volume – a measure of the size of a body or region in 3 dimensional space Volume – a measure of the size of a body or region in 3 dimensional space How do you measure the volume of… How do you measure the volume of…

Mass vs. Weight Mass – the measure of the amount of matter in an object Mass – the measure of the amount of matter in an object –Measured with what? Weight – a measure of the gravitational force exerted on an object Weight – a measure of the gravitational force exerted on an object What’s the difference? What’s the difference?

Units of Measurement Qualitative description – describes qualities/appearance ex: large, small, texture, color Qualitative description – describes qualities/appearance ex: large, small, texture, color Quantative description – describes numbers ex: 15 grams, 125 pounds Quantative description – describes numbers ex: 15 grams, 125 pounds Quantity – something that has magnitude or size Quantity – something that has magnitude or size

Units of Measure Unit – a standard used when measuring a quantity ex: 15 grams (grams is the unit) Unit – a standard used when measuring a quantity ex: 15 grams (grams is the unit) Every numerical measurement must have a quantity and a unit!!! Every numerical measurement must have a quantity and a unit!!!

SI Units MeasurementQuantityUnit 15 kilograms 15kilograms 30 millimeters 30millimeters

The Measurement System of Science Do these mean anything to you? Do these mean anything to you? Kilo: Kilo: –kilometer, kilogram Centi: Centi: –centimeter, cents, century Deca Deca –Decathlon, decade

SI Units Scientists use a system called the SI System Scientists use a system called the SI System –Allows for universal measurements –Enables you to use more manageable numbers SI units chart and SI prefixes chart SI units chart and SI prefixes chart

SI Prefixes! UnitSymbolMeaning MegaM1M(b.u.) = 1,000,000 (b.u.) Kilok1k(b.u.) = 1,000 (b.u.) Hectoh1h(b.u.) = 100 (b.u.) Decada1da(b.u.) = 10 (b.u.) Base Unit Decid10 d(b.u.) = 1 (b.u.) Centic100 c(b.u.) = 1 (b.u.) Millim1,000 m(b.u.) = 1 (b.u.) Microμ1,000,000 μ(b.u.) = 1 (b.u.)

So what? How do we use them? Any SI unit has two parts: Any SI unit has two parts: –prefix –base For example, For example, –kilo-gram –kilo-meter –centi-meter –centi-gram So, what do we call 10 grams? So, what do we call 10 grams? –deca-gram What do we call.001 seconds? What do we call.001 seconds? –milli-second How about.1 liters? How about.1 liters? –deci-liter

Conversion Factors Conversion Factor – a mathematical expression that relates two units Conversion Factor – a mathematical expression that relates two units Quarters and dollars conversion factor – 4 quarters = 1 dollar Quarters and dollars conversion factor – 4 quarters = 1 dollar Convert 18 quarters to dollars Convert 18 quarters to dollars

Conversions Start with what you know Start with what you know What you are going to goes in the top and coming from goes in the bottom What you are going to goes in the top and coming from goes in the bottom Convert 3 dollars to quarters Convert 3 dollars to quarters

Conversions Convert 45 minutes to hours. Convert 45 minutes to hours hours 0.75 hours Convert 2.5 hours to minutes. Convert 2.5 hours to minutes. 150 minutes 150 minutes

Conversions Convert 100 millimeters to meters Convert 100 millimeters to meters 1 meter = 1000millimeters 1 meter = 1000millimeters 0.1m 0.1m Convert 3 hours to seconds Convert 3 hours to seconds 10,800 seconds 10,800 seconds

Conversions Convert 0.12 kg to mg Convert 0.12 kg to mg Must convert to base unit first if going from one side to the other. Must convert to base unit first if going from one side to the other. Convert 130 cm to Mm Convert 130 cm to Mm

Derived Units When 7 main don’t cover it Speed = distance over time or meters/second Rectangle = l x w = m 2 Common for chemistry is 1 L = 1000 mL = 1000 cm 3

Properties of Matter Physical Property – a characteristic of a substance that does not involve a chemical change - ex: density, color, melting point, b.p., texture Physical Property – a characteristic of a substance that does not involve a chemical change - ex: density, color, melting point, b.p., texture Also can be seen by the absence of something like color Also can be seen by the absence of something like color – it’s colorless

Properties of Matter Chemical Property – a property of matter that describes a substances ability to participate in chemical rxns Chemical Property – a property of matter that describes a substances ability to participate in chemical rxns ex: iron rusts in the presence of oxygen, acids react with bases to form salts ex: iron rusts in the presence of oxygen, acids react with bases to form salts

Specific Physical Property Density – the ratio of mass to volume D=m/v Density – the ratio of mass to volume D=m/v Usually expressed as g/cm 3 for solids and g/L for gases Usually expressed as g/cm 3 for solids and g/L for gases Does not depend on how much of the substance you have Does not depend on how much of the substance you have

Density Silver Bracelet Silver Bracelet Mass is g and when it displaces water, volume is 20.5 cm 3 Mass is g and when it displaces water, volume is 20.5 cm 3 Density of silver is 10.5 g/cm 3 Density of silver is 10.5 g/cm 3 Is this a silver bracelet? Is this a silver bracelet?

Density Calculations A piece of an unknown material has a mass of 5.85 g and a volume of 7.57 cm 3. What is the density of the material? A piece of an unknown material has a mass of 5.85 g and a volume of 7.57 cm 3. What is the density of the material?

Density Calculations D = m D = m v D = m = 5.85 g D = m = 5.85 g v 7.57 cm 3 v 7.57 cm 3 Density = 0.77 g/cm 3 Density = 0.77 g/cm 3

Density calculations A 200 g piece of metal has a volume of 25 cm 3. Calculate the density of the metal. A 200 g piece of metal has a volume of 25 cm 3. Calculate the density of the metal. An unknown mass of silicon occupies a volume of 350 cm 3. Calculate the mass of Si knowing that the density of Si is 2.34 g/cm 3. An unknown mass of silicon occupies a volume of 350 cm 3. Calculate the mass of Si knowing that the density of Si is 2.34 g/cm 3.

Density What is the volume that a 50 gram piece of gold occupies? The density of gold is 19.30g/cm 3. What is the volume that a 50 gram piece of gold occupies? The density of gold is 19.30g/cm 3.

Assignment Complete Section Review on page 19 numbers Complete Section Review on page 19 numbers This is due tomorrow. This is due tomorrow.