Measurements and the Metric System The Metric System
- Slides: 19
Measurements and the Metric System
The Metric System • A universal measurement system • Also called the International System or SI units • Only three countries worldwide don’t use the metric system (USA, Burma, and Liberia)
The Metric System • Based on multiples of ten (this makes it easy to use) • Uses prefixes to identify larger or smaller units of measure Common Symbol Multiple Prefixes kilo K 1000 centi c . 01 milli m . 001
Metric Conversions - Length x 1000 Km ÷ 1000 x 10 m x 10 dm ÷ 10 x 10 cm ÷ 10 mm ÷ 10
Metric Conversions - Volume x 1000 Kl x 10 l ÷ 1000 x 10 dl ÷ 10 x 10 cl ÷ 10 ml ÷ 10
Metric Conversions - Mass x 1000 Kg x 10 g ÷ 1000 x 10 dg ÷ 10 x 10 cg ÷ 10 mg ÷ 10
Length • A measure of linear distance • Basic unit of length is the meter (m) • Measurements made with a meter stick or metric ruler • The entire meter stick represents one meter • Each number represents a centimeter (there are 100 centimeters in a meter) • Each little line is a millimeter (there are 1000 millimeters in a meter)
Area • The amount of surface included within a set of boundaries • Determined by measuring the length and width of an object, then multiplying Length = 14 cm Width = 7 cm Area = 14 cm x 7 cm = 98 cm 2 (Area is always expressed in square units)
Volume • Volume is the space that an object occupies • Represents the length, width, and height of an object • For solids, measurements are based on units of length (ex. cm 3) and can be calculated using specific formulas
Calculating the volume of a rectangular prism Volume of a rectangular prism = length x width x height (l x w x h) 4 cm Length = 10 cm Width = 3 cm Height = 4 cm 3 cm 10 cm Volume = l x w x h = 10 cm x 3 cm x 4 cm = 120 cm 3
Calculating the volume of a cylinder Diameter = 10 cm 20 cm
Volume of a liquid • A graduated cylinder is used to accurately measure the volume of liquids in milliliters • Determine the volume in a graduated cylinder by reading the bottom of the meniscus at eye level • Once the volume of a liquid is known, it can be converted to a “solid volume” by using the formula 1 ml = 1 cm 3
Mass • Mass is a measure of the amount of matter in an object • Mass is measured in grams using a balance • The mass of an object remains the same, no matter where in the universe it is measured
Weight is a measure of the gravitational force exerted on an object by a massive body • Weight is measured in Newtons (N) using a spring scale • Weight varies from place to place depending on the strength of the gravitational force Your weight on Earth = Mass (Kg) X 9. 8 m/s² (Earth’s surface gravity) For a person with a mass of 45 Kg Weight = 45 Kg X 9. 8 m/s² = 441 N
Gravity is the force of attraction between objects The strength of the gravitational force between objects depends on: - The distance between the objects ( the gravitational force between objects decreases with distance) -Mass ( the greater the mass of an object, the greater it’s gravitational force)
Density • Density is the mass of a specific volume of an object • Density is calculated by dividing the mass of an object by its volume • Units for density are usually expressed in grams per cubic centimeter (g/cm 3 ) • Since the density of water is 1 g/cm 3 anything with a density less than 1 g/cm 3 will float in water and anything greater will sink
Calculating Density A 3 cm Volume of Object A = 5 cm x 2 cm x 3 cm = 30 cm³ Mass of Object A = 150 grams (measured on a balance) 2 cm 5 cm Density = Mass Volume Density of Object A = 150 grams = 5 g/cm³ 30 cm³
Calculating Density 4 cm 2 cm 4 cm 4 cm 1 cm
Density Challenge 1. Find two objects, one a solid and the other a liquid that have the same density 2. Be able to demonstrate their similar densities by showing that the solid object will suspend itself within the liquid 3. Rules: 1. Solid must be suspended and not trapped 2. May not use any harmful or dangerous products 3. Must bring in the two substances and then demonstrate your solution in the classroom 4. A correct solution would be worth 10 bonus points on the upcoming test 5. Deadline to meet the challenge is Thursday, 10/18
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