1 Scientific Measurement Objectives: Distinguish between quantitative and qualitative measurements. Convert measurements to scientific notations. List common SI units of measurement and common prefixes used in the SI system. Distinguish mass, weight, volume, length and density.

2 Measurements * However, a measurement cannot be more reliable than the instrument and the care with which it is used and read.

3 Identify the following as quantitative or qualitative measurements. A.The flame is hot. B.A candle has a mass of 90 g. C.Wax is soft. D. A candle’s height decreases 4.2 cm/h. The speed limit is 65 mph, you go 10 mph faster. How fast are you going? too fast or very fast Quantitative statement: 75 mph Qualitative statement: quantitative qualitative quantitative qualitative

4 Scientific Notation Estimated number of stars in a galaxy

5 Scientific notation is a way of writing numbers that are very big or small. Example: Standard From Scientific Notation 520,000, x 10 8 In scientific notation: a number is written as the product of two numbers; a coefficient between 1 and 10 and 10 raised to a power: 3.5 x 10 3 Coefficient 5.2 x 10 8 Exponent

6 Scientific Notation

7 If the exponent is positive, the number is bigger than 1 (Move decimal point to the right to write scientific notation as regular number) If the exponent is negative, the number is between 0 and 1 Example: 3500 Example : 0.025

8 In scientific notation, a number is written as the product of two numbers: a coefficient (  1and <10) and 10 raised to a power. Examples: 3.6 x 10 4 = 3.6 x 10 x 10 x 10 x 10 = x = 8.1. = x 10 x 10 Scientific Notation Convert to scientific notation: 3600 m cm 999 Kg314 ml 8.5 x 10 4 = ??? 1.0 x =??? 6.21 x = ??? 5.2 x =???

9 Using scientific notation makes calculating more straightforward: To multiply numbers written in scientific notation… Multiply the coefficients and add the exponents. (3.0 x 10 4 ) x (2.0 x 10 2 ) = (3.0 x 2.0) x = 6.0 x 10 6 Now you try… (5.5 x 10 5 ) x (2.0 x 10 3 ) = ?

10 To divide numbers written in scientific notation… Divide the coefficients and subtract the exponents. (3.0 x 10 4 ) = 3.0 x = 1.5 x 10 2 (2.0 x 10 2 )2.0 Now you try… (8.8 x 10 9 ) = ? (2.0 x 10 3 )

11 Often, it is useful to calculate the relative error, or percent error. The percent error is the absolute value of the error divided by the accepted value, multiplied by 100%. Using the absolute value of the error means that the percent error will always be a positive value. Percent Error |error | Percent Error = X 100% = accepted value | accepted value — experimental value | = X 100% accepted value Calculate the percent error, if the accepted value is 100°C and the experimental value is 99.3 °C

12 Scientific Measurement Objectives: List common SI units of measurement and common prefixes used in the SI system. Distinguish mass, volume, density and length.

13 “Walk five in that direction” All measurements depend on units that serve as reference standards ? ? The standards of measurements used in science are those of the metric system. All units are based on 10 or multiples of 10, which makes it simple to use.

14 The International System of Units (SI) is a revised version of the metric system. There are seven SI base units, from which all other units are derived. SI base units Derived units are volume, density, pressure, energy etc.

15 Sometimes non-SI units are preferred for practical reasons examples are liter for volume degree Celsius for temperature atmosphere or millimeter of mercury for pressure calorie for energy

16 Commonly Used Prefixes in the Metric System Examples: 1 km = 1000 m = 1x 10 3 m 1 mg = 0.001g = 1x g 1  g = g = 1x g

17 1 meter 100 centimeters Smaller numberLarger unit Larger number Smaller unit Whenever you convert units, the two measurements must remain equivalent For example:1 m = 100 cm

18 Metric Units of Length 5 mm = ? m 5 km = ? m 5 nm = ? m = m (move decimal place three times) = m ( “ “ “ “ to the right) = m = 5 x m

19 1 meter  1.1 yard or 3.2 ft;height from floor to door knob 1 mile  1.6 km 1 km about 5 City blocks 1 dm  4 inches; the diameter of an orange 1 inch = 2.54 cm 1 cm  length of each side of a sugar cube 1  m  diameter of bacterial cell 1 nm  thickness of RNA molecule

20 The space occupied by any sample of matter is called its volume. (length X height X width for a cube) => m x m x m = m 3 cubic meter; e.g. size of a dishwasher More convenient is liter (L), a non-SI unit 1 L = 10cm x 10cm 10cm = 1000 cm 3 Units of Volume

21 Laboratory Glassware used to measure volume Erlenmeyer Buret Graduated beaker Volumetric flask cylinder Flask

22 Units of Mass Mass is a measure of the quantity of matter, constant, regardless of its location Weight is a force of gravity exerted on a given mass, which varies depending on its location 1 kg is 1 L of liquid water at 4 °C or 1 g is 1 cm 3 of liquid water at 4 °C

23 Density Density is the ratio of the mass of an object to its volume mass Density = volume Density depends only on the composition of a substance, not on the size of the sample

24 Relationship Between Volume and Density

25 density decreases with increase in temperature Usually the density decreases with increase in temperature and a substance has a higher density in the solid state than as a liquid. Ice/cold water What is the exception? As a gas or vapor every substance has a lower density compared to its liquid and solid states.

26 Calculating Density A copper Penny has a mass of 3.1g and a volume of 0.35 cm 3 What is the density of copper? 1.Analyze: mass = 3.1 g, volume = 0.35cm 3 density = ? g/cm 3 2. Calculate: Solve for the Unknown density = mass/volume = 3.1g/0.35cm 3 = g/cm 3 g/cm 3 (rounded to two decimals =8.86 g/cm 3 3. Evaluate Does the results make sense? about 0.33cm 3 has a mass 3 g, a volume three times that much is about 1 cm 3, should have a mass of about 9 grams. This estimate agrees with calculated density.

27 1. Analyze: KnownUnknown mass = 57.9 g, volume = 3.00 cm 3 density = ? g/cm 3 2. Calculate: Solve for the Unknown density = mass/volume = 57.9g/3.00cm 3 = 19.3 g/cm 3 3. Evaluate Does the results make sense? 3 cm 3 of gold have a mass of about 60 g, a third of that volume is 1 cm 3, should have a mass of about 60/3 = 20 grams. This estimate agrees with calculated density g of gold occupy a volume of 3.00 cm 3. Calculate the density

28 density of substance (g/cm 3 ) Specific Gravity = density of water (g/cm 3) Hydrometer weight Liquid being measured Specific gravity read here

29 Temperature Scales Metric Unit for Temperature is Degree Celsius (reference points boiling point and freezing point of water) SI Unit for Temperature is Kelvin without degree sign (reference points is absolute zero = -273 °C) Conversion: K= °C °C = K Kelvin of water °C Freezing point 273K Celsius 100°C Boiling point 373K 100 divisions