CHAPTER 1 The Science of Chemistry 1.1 What Chemistry Is About
Measurements Using clear standards of measurements, we can communicate more effectively in answering simple questions. 2 1.1 What Chemistry Is About
Measurements Mass How heavy is an egg? Volume How much space does an egg occupy? Density Does an egg size piece of steel or wood have the same mass? Pressure How hard is it to crush an egg by squeezing evenly from all sides? 3 1.1 What Chemistry Is About
Measurements Mass How heavy is an egg? Volume How much space does an egg occupy? Density Does an egg size piece of steel or wood have the same mass? Pressure How hard is it to crush an egg by squeezing evenly from all sides? 4 1.1 What Chemistry Is About
Mass The size (or volume) does not tell us how much matter there is. 5 1.1 What Chemistry Is About
Mass Remember: Size (volume) does not tell us how much matter there is. 1,000 g = 1 kg 6 1.1 What Chemistry Is About
Measurements Mass How heavy is an egg? Volume How much space does an egg occupy? Density Does an egg size piece of steel or wood have the same mass? Pressure How hard is it to crush an egg by squeezing evenly from all sides? 7 1.1 What Chemistry Is About
Volume Volume indicates an amount of space. The milliliter (ml) is a unit of volume. 8 1.1 What Chemistry Is About
You can measure the volume of a liquid using a graduated cylinder. Volume 75 ml 9 1.1 What Chemistry Is About
You can measure the volume of a liquid using a graduated cylinder. Volume 1 ml = 1 cm 3 10 1.1 What Chemistry Is About
Measurements Mass How heavy is an egg? Volume How much space does an egg occupy? Density Does an egg size piece of steel or wood have the same mass? Pressure How hard is it to crush an egg by squeezing evenly from all sides? 11 1.1 What Chemistry Is About
Density 3 blocks of equal volume plastic glass iron 3 different mass values 12 1.1 What Chemistry Is About
Relationship between mass and volume density: a property of a substance that describes how much matter the substance contains per unit volume; typical units are grams per cubic centimeter (g/cm 3 ). 13 1.1 What Chemistry Is About
If 45 g of titanium are added to a graduated cylinder containing 50 ml of water, what will the cylinder read after the titanium has been added? Density 14 1.1 What Chemistry Is About
Density If 45 g of titanium are added to a graduated cylinder containing 50 ml of water, what will the cylinder read after the titanium has been added? Asked: Given: Relationships: Volume of graduated cylinder after adding 45 g of titanium 45 g of titanium, density of titanium d = 4.5 g/cm 3, 50 ml of water d m V 15 1.1 What Chemistry Is About
Density If 45 g of titanium are added to a graduated cylinder containing 50 ml of water, what will the cylinder read after the titanium has been added? Asked: Given: Relationships: Solve: Answer: Discussion: Volume of graduated cylinder after adding 45 g of titanium 45 g of titanium, density of titanium d = 4.5 g/cm 3, 50 ml of water d m V m 45 g 1.0 ml V 10 ml 3 3 d 4.5 g cm cm The titanium adds 10 ml to the cylinder, which now reads 60 ml. 60 ml This is an example of measurement using the displacement method. 16 1.1 What Chemistry Is About
Measurements Mass How heavy is an egg? Volume How much space does an egg occupy? Density Does an egg size piece of steel or wood have the same mass? Pressure How hard is it to crush an egg by squeezing evenly from all sides? 17 1.1 What Chemistry Is About
Is the mass exactly 10.0 g? Accuracy and precision Could it be 9.96 g? 10.04 g? We don t know since any mass between 9.95 g and 10.05 g would round off to 10.0 g 18 1.1 What Chemistry Is About
Accuracy and precision Measurements that are not accurate could lead you to the wrong conclusion. If a measurement is not precise, you may not be able to tell the difference between agreement and disagreement. 19 1.1 What Chemistry Is About
Accuracy how close a measurement is to the true (correct) value. Precision, how close the measured values are to each other. These values may be incorrect or correct. 20 1.1 What Chemistry Is About
Significant figures Do you record 10 g or 10.0 g? Does it make a difference? 21 1.1 What Chemistry Is About
Significant figures Do you record 10 g or 10.0 g? Does it make a difference? Yes, it makes a difference in precision 22 1.1 What Chemistry Is About
If you record 10 g 9 10 11 If you record 10.0 g 23 1.1 What Chemistry Is About
What value should be recorded for the volume measurement in the picture? Precision and accuracy 24 1.1 What Chemistry Is About
What value should be recorded for the volume measurement in the picture? Precision and accuracy Asked: Given: Relationships: The value with the correct number of significant figures You can estimate to a tenth of the graduation of a cylinder or ruler The last digit on the right is assumed to be plus or minus one-tenth. 25 1.1 What Chemistry Is About
What value should be recorded for the volume measurement in the picture? Precision and accuracy Asked: Given: Relationships: Solve: Answer: The value with the correct number of significant figures You can estimate to a tenth of the graduation of a cylinder or ruler The last digit on the right is assumed to be plus or minus one-tenth. The meniscus is right on 18, so estimate 18.0 ml. 18.0 ml Discussion: The real value is confidently known to be between 17.9 and 18.1 ml. 26 1.1 What Chemistry Is About
1 sigfig 3 sigfigs 1 sigfig 27 1.1 What Chemistry Is About
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Science encompasses very large and very small objects. Large Small The scientific notation is a shorthand system to write very large and very small numbers 31 1.1 What Chemistry Is About
Scientific notation mantissa 1,500 = 15 x 100 power of 10 32 1.1 What Chemistry Is About
Scientific notation mantissa 1,500 = 15 x 100 = 10 2 100 = 10 x 10 = 10 2 exponent 33 1.1 What Chemistry Is About
Scientific notation mantissa 1,500 = 15 x 100 mantissa = 10 2 1,500 = 1.5 x 1,000 = 10 3 34 1.1 What Chemistry Is About
Scientific notation 1,500 in scientific notation: 1.5 x 10 3 mantissa 1,500 = 1.5 x 1,000 = 10 3 35 1.1 What Chemistry Is About
Scientific notation 40,000,000 = 4 x 10 7 3,600 = 3.6 x 10 3 83,100 = 8.31 x 10 4 36 1.1 What Chemistry Is About
Scientific notation mantissa 0.0015 = 1.5 x 0.001 power of 10 37 1.1 What Chemistry Is About
Scientific notation mantissa 0.0015 = 1.5 x 0.001 = 10 3 A negative exponent means: the number is smaller than 1 does not mean: the whole number is negative 38 1.1 What Chemistry Is About
Scientific notation mantissa 0.0015 = 1.5 x 0.001 = 10 3 0.0015 in scientific notation: 1.5 x 10 3 39 1.1 What Chemistry Is About
Scientific notation 0.000 000 4 = 4 x 10 7 0.003 6 = 3.6 x 10 3 0.000 083 1 = 8.31 x 10 5 40 1.1 What Chemistry Is About
Scientific notation Convert 0.00065 to scientific notation. Asked: Given: 4 Relationships: 0.0001 10 The number in scientific notation 0.00065 as a decimal number 41 1.1 What Chemistry Is About
Scientific notation Convert 0.00065 to scientific notation. Asked: Given: Relationships: Answer: The number in scientific notation 0.00065 as a decimal number 0.0001 10 4 6.5 10 4 42 1.1 What Chemistry Is About
Using scientific notation on a calculator Scientific notation 43 1.1 What Chemistry Is About
Measuring physical properties Precision vs. accuracy Mass Volume Density Pressure grams liters grams per liter atmospheres, psi Scientific notation 40,000,000 = 4 x 10 7 0.000 000 4 = 4 x 10 7 44 1.1 What Chemistry Is About