1 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 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? Measurements 3 1.1 What Chemistry Is About 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? Measurements 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 Which of these has more mass? What are the standards of comparison? Mass of a 1-L bottle of water Mass of a single peanut Mass 6 1.1 What Chemistry Is About 1 gram1,000 grams Mass of a single peanut The gram is a unit of mass Mass Mass of a 1-L bottle of water 7 1.1 What Chemistry Is About Mass 1,000 g = 1 kg Remember: Size (volume) does not tell us how much matter there is. 8 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? 9 1.1 What Chemistry Is About Volume indicates an amount of space. The milliliter (mL) is a unit of volume. Volume What Chemistry Is About You can measure the volume of a liquid using a graduated cylinder. 75 mL Volume What Chemistry Is About Volume 1 mL = 1 cm 3 You can measure the volume of a liquid using a graduated cylinder. 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? What Chemistry Is About 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? Measurements What Chemistry Is About Is the mass exactly 10.0 g? We dont know since any mass between 9.95 g and g would round off to 10.0 g Accuracy and precision Could it be 9.96 g? g? 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. What Chemistry Is About Significant figures Do you record 10 g or 10.0 g? Does it make a difference? What Chemistry Is About Significant figures Yes, it makes a difference in precision Do you record 10 g or 10.0 g? Does it make a difference? What Chemistry Is About If you record 10 g If you record 10.0 g What Chemistry Is About Precision and accuracy What value should be recorded for the volume measurement in the picture? What Chemistry Is About What value should be recorded for the volume measurement in the picture? Precision and accuracy Asked: The value with the correct number of significant figures Given:You can estimate to a tenth of the graduation of a cylinder or ruler Relationships:The last digit on the right is assumed to be plus or minus one-tenth. What Chemistry Is About Precision and accuracy Asked: The value with the correct number of significant figures Given:You can estimate to a tenth of the graduation of a cylinder or ruler Relationships:The last digit on the right is assumed to be plus or minus one-tenth. Solve:The meniscus is right on 18, so estimate 18.0 mL. Answer:18.0 mL Discussion:The real value is confidently known to be between 17.9 and 18.1 mL. What value should be recorded for the volume measurement in the picture? What Chemistry Is About Science encompasses very large and very small objects. The scientific notation is a shorthand system to write very large and very small numbers Large Small What Chemistry Is About Scientific notation 1,500 = 15 x 100 mantissa power of 10 What Chemistry Is About 1,500 = 15 x 100 mantissa = = 10 x 10 = 10 2 exponent Scientific notation What Chemistry Is About 1,500 = 15 x 100 mantissa = ,500 = 1.5 x 1,000 = 10 3 mantissa Scientific notation What Chemistry Is About 1,500 in scientific notation: 1.5 x ,500 = 1.5 x 1,000 = 10 3 mantissa Scientific notation What Chemistry Is About 40,000,000 = 4 x ,600 = 3.6 x ,100 = 8.31 x 10 4 Scientific notation What Chemistry Is About = 1.5 x mantissa power of 10 Scientific notation What Chemistry Is About = 1.5 x mantissa = 10 3 A negative exponent means: the number is smaller than 1 does not mean: the whole number is negative Scientific notation What Chemistry Is About in scientific notation: 1.5 x 10 = 1.5 x mantissa Scientific notation = 10 3 What Chemistry Is About = 4 x 10 = 3.6 x 10 = 8.31 x 10 5 Scientific notation What Chemistry Is About Convert to scientific notation. Scientific notation Asked:The number in scientific notation Given: as a decimal number Relationships: What Chemistry Is About Convert to scientific notation. Scientific notation Asked:The number in scientific notation Given: as a decimal number Relationships: Answer: What Chemistry Is About Using scientific notation on a calculator Scientific notation What Chemistry Is About Convert $1.25 / L to dollar per gallon. Unit conversions What Chemistry Is About Convert $1.25 / L to dollar per gallon. Unit conversions Asked: A value in dollars per gallon Given:$1.25/L Relationships:1 gallon = L What Chemistry Is About Convert $1.25 / L to dollar per gallon. Unit conversions Asked: A value in dollars per gallon Given:$1.25/L Relationships:1 gallon = L Solve: Answer:$4.73/gallon What Chemistry Is About Measuring physical properties Massgrams Volumeliters Densitygrams per liter Pressureatmospheres, psi Precision vs. accuracy Scientific notation 40,000,000 = 4 x = 4 x 10 7