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Describing Matter

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?. Chemistry investigates the nature of matter.

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Describing Matter

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  1. Describing Matter 1.2

  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?

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

  4. Mass vs. Weight • 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 • What’s the difference?

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

  6. Units of Measure • 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!!!

  7. SI Units

  8. SI Units (the Metric system) The Measurement System of Science • Do these mean anything to you? • Kilo: • kilometer, kilogram • Centi: • centimeter, cents, century • Deca • Decathlon, decade

  9. SI Units • 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

  10. SI Prefixes!

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

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

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

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

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

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

  17. Derived Units • When 7 main don’t cover it • Speed = distance over time or meters/second • Rectangle = l x w = m2 • Common for chemistry is 1 L = 1000 mL = 1000 cm3

  18. 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 • Also can be seen by the absence of something like color • it’s colorless

  19. Properties of Matter • 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

  20. Specific Physical Property • Density – the ratio of mass to volume D=m/v • Usually expressed as g/cm3 for solids and g/L for gases • Does not depend on how much of the substance you have

  21. Density • Silver Bracelet • Mass is 100.0 g and when it displaces water, volume is 20.5 cm3 • Density of silver is 10.5 g/cm3 • Is this a silver bracelet?

  22. Density Calculations • A piece of an unknown material has a mass of 5.85 g and a volume of 7.57 cm3.  What is the density of the material?

  23. Density Calculations • D = m v • D = m = 5.85 g v 7.57 cm3 • Density = 0.77 g/cm3

  24. Density calculations • A 200 g piece of metal has a volume of 25 cm3. Calculate the density of the metal. • An unknown mass of silicon occupies a volume of 350 cm3. Calculate the mass of Si knowing that the density of Si is 2.34 g/cm3.

  25. Density • What is the volume that a 50 gram piece of gold occupies? The density of gold is 19.30g/cm3.

  26. Assignment • Complete Section Review on page 19 numbers 1-12. • This is due tomorrow.

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