 # Introduction to Chemistry.  Matter  Mass  Weight.

## Presentation on theme: "Introduction to Chemistry.  Matter  Mass  Weight."— Presentation transcript:

Introduction to Chemistry

 Matter  Mass  Weight

 Scientific Methods  Qualitative data  Quantitative data

 Independent Variable  Dependent Variable  Control

 Theory  Law

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

◦ Volume ◦ Density

 460,000,000,000,000,000,000,000

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

 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

 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

 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?

 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.

 Uncertainty  Accuracy  Precision

 Using tools to make measurements

 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.

 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