# Measurements and Calculations Chapter 2 Honors Chemistry Garcia.

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Measurements and Calculations Chapter 2 Honors Chemistry Garcia

2-1 Objectives Describe the purpose of the scientific method. Describe the purpose of the scientific method. Distinguish between qualitative and quantitative observations. Distinguish between qualitative and quantitative observations. Describe the differences between hypotheses, theories, and models. Describe the differences between hypotheses, theories, and models.

Scientific Method logical approach to: solving problems by observing & collecting data solving problems by observing & collecting data formulating hypotheses formulating hypotheses testing hypotheses testing hypotheses formulating theories that are supported by data formulating theories that are supported by data

Quantitative vs. Qualitative quantitative measurement- numerical information qualitative measurement- descriptive, non- numerical information system- specific portion of matter in a given region of space that is being studied

Scientific Method hypothesis- educated guess; testable statement model- explanation of how things occur and how data/events are related theory- broad generalization that explains a body of facts

2-2 Objectives Distinguish between a quantity, a unit, and a measurement standard. Distinguish between a quantity, a unit, and a measurement standard. Name SI units for length, mass, time, volume, and density. Name SI units for length, mass, time, volume, and density. Distinguish between mass and weight. Distinguish between mass and weight. Perform density calculations. Perform density calculations. Transform a statement of equality to a conversion factory. Transform a statement of equality to a conversion factory.

Le System International d’Unites SI system- International System of Units adopted in 1960 Seven base units: length length mass mass time time temperature temperature amount of a substance amount of a substance electric current electric current luminous intensity luminous intensity

QuantitySymbol Unit Name Unit Abbreviation lengthlmeterm massmkilogramkg timetseconds temperatureTkelvinK amount of a substance nmolemol electric current IampereA luminous intensity IVIVIVIVcandelacd

prefix unit abbreviation exponential factor meaning teraT 10 12 1 trillion gigaG 10 9 1 billion megaM 10 6 1 million kilok 10 3 1000 hectoh 10 2 100 dekada 10 1 10

prefix unit abbreviation exponential factor meaning decid 10 -1 1/10 centic 10 -2 1/100 millim 10 -3 1/1000 micro 10 -6 1/1000000 nanon 10 -9 1/1000000000 picop 10 -12 1/1000000000000 femtof 10 -15 1/1000000000000000 attoa 10 -18 1/1000000000000000000

Units of Measurement derived units- a combination of SI base units quantitysymbolunitabbreviationderivation areaA square meter m2m2m2m2 length x width volumeV cubic meter m3m3m3m3 length x width x height densityD kilograms per cubic meter kg/m 3 mass/volume molar mass M kilograms per mole kg/mol mass/amount of substance concentrationc moles per liter M amount of substance/volume molar volume VmVmVmVm cubic meters per mole m 3 /mol volume /amount of substance energyEjouleJ force x length

Units of Measurement volume- amount of space occupied by an object 1 cm 3 = 1 mL density- ratio of mass to volume D = m/v

What is the density of a block of marble that occupies 310 cm 3 and has a mass of 853 g?

Diamond has a density of 3.26 g/cm 3. What is the mass of a diamond that has a volume of 0.350 cm 3 ?

Conversion Factors conversion factor- ratio derived from the equality between two different units ex. seconds to hours feet to inches

You have a chili recipe that serves ten. The recipe calls for two teaspoons of chili powder. How much chili powder do you need for 600 servings?

How many seconds are there in one day?

Express 750 dg in grams.

Convert 0.107 g to kilograms.

What is 0.073 cm in micrometers?

2-3 Objectives Distinguish between accuracy and precision. Distinguish between accuracy and precision. Determine the number of significant figures in measurements. Determine the number of significant figures in measurements. Perform mathematical operations involving significant figure. Perform mathematical operations involving significant figure. Convert measurements into scientific notation. Convert measurements into scientific notation. Distinguish between inversely and directly proportional relationships. Distinguish between inversely and directly proportional relationships.

Accuracy vs. Precision accuracy- closeness of measurements to the correct or accepted value precision- closeness of a set of measurements of the same quantity made in the same way

Percent Error accepted value – experimental value x 100 accepted value

What is the percent error for a mass measurement of 17.7 g, given that the correct value is 21.2 g?

A volume is measured experimentally as 4.26 mL. What is the percent error, given that the correct value is 4.15 mL?

Significant Figures measurement of all known digits with certainty plus one estimated digit 1. zeros between nonzero digits are significant 320110150002 2. zeros appearing before nonzero digits are not significant 0.00430.3580.0302

Significant Figures 3. zeros at the end of a number & to the right of a decimal point are significant 62.03.000029.000000 4. zeros at the end of a number but the left of a decimal may or may not be significant; a decimal point placed after the zeros indicate they are significant 45004500.3200000.