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Introduction to Chemistry

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Matter Mass Weight

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Scientific Methods Qualitative data Quantitative data

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Independent Variable Dependent Variable Control

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Theory Law

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There are seven SI base units. Time: Length: Mass: Temperature:

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◦ Volume ◦ Density

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460,000,000,000,000,000,000,000

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The diameter of the sun is 1,392,00 km

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In order to add and subtract numbers in scientific notation, the exponents must be the same. 2.840 x 10 18 3.146 x 10 18 3.60 x 10 17 1.50 x 10 17 6.9 x 10 16 6.565 x 10 18

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For multiplication, multiply the numbers and then add the exponents. (2 x 10 3 ) x (3 x 10 2 ) 2 x 3 = 6 3 + 2 = 5 6 x 10 5 For division, divided the numbers and then subtract the exponent of the divisor from the exponent of the dividend. (9 x 10 8 ) ÷ (3 x 10 -4 ) 9 ÷ 3 = 3 8 – (-4) = 8 +4 = 12 3 x 10 12

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Dimensional Analysis How many pizzas do you need to order if 32 people will attend a party, each person eats 3 slices of pizza, and each pizza has 8 slices?

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We can do the same types of conversions with SI units. We just need to know the relationship between the units we want to convert. Examples: We know that there are 1000 m in 1 km. We can rewrite this as: 1000m/1km or 1km/1000m Then if we are given and number of meters or kilometers we can convert. Convert 48 km into meters.

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Uncertainty Accuracy Precision

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Using tools to make measurements

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1. Zeros between nonzero digits are always significant. ◦ 1005 kg – Has 4 significant figures 2. Zeros at the beginning of a number are never significant. ◦ 0.02 g – Has one sig. fig. ◦ 0.0025 - Has two sig. figs. 3. Zeros at the end of a number are significant only if there is a decimal in the number. ◦ 0.0200 g – Has three sig. figs. ◦ 3.0 cm – Has two sig. figs. ◦ 100 cm – Has only one sig. fig.

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When we use measured quantities to do calculations, the least certain measurement limits the certainty of our calculation. Therefore the number of significant figures in our answer is determined by the number of sig figs in the least certain number. Rules: ◦ For addition and subtraction: The answer has the same number of decimal places as the number with the least amount of decimal places. ◦ 20.42 + 1.322 + 83.1 = 104.842, we round to 104.8 ◦ For multiplication and division: The answer has the same number of sig figs as the number with the smallest number of sig figs. ◦ 6.221 x 5.2 = 32.3492, we round to 32

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