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MEASUREMENT UNIT REVIEW NOTES TO BE USED WITH CHART GENERAL NOTES ABOUT MEASUREMENT: Why is the metric system of measurement easier to use than the English Standard System? It’s easy to convert from larger to smaller units and vice-versa because it’s based on the number 10 and its multiples. Also, to convert you only have to move the decimal right or left. Why do scientists all over the world use the metric system as their standard system of measurement? So that they can compare and contrast their scientific data and communicate with each other using the same units of measurements; also because of its simple conversion formula. LENGTH: - Definition - a measure of the distance from point A to B. - A metric ruler is divided into 30 centimeters. It is the closest measurement to a foot. - Each centimeter is divided into 10 millimeters. - A meter is the closest measurement to a yard. MASS: - Definition - a measure of the amount of matter an object contains. - The difference between mass and weight is that weight is a measure of the force of gravity acting on an object whereas mass only measures the amount of matter an object contains. - Your mass and weight on Earth are the same because of gravity, but if you were to weigh yourself on the moon, which has a much weaker force of gravity, you would weigh less. Your mass would still be the same. Parts of a triple beam balance - Pan, adjuster, beams, pointer, riders How to use one: 1) Make sure the balance is zeroed out by turning the adjuster until the pointer is lined up with 0 at eye level. 2) Place object that you are getting mass of in the middle of the pan. 3) Move 100g rider (middle beam) first, then 10g rider (top beam), then 1g rider (bottom rider) until pointer is lined up with 0. Highest mass a triple beam balance can measure – 610g VOLUME: Definition – a measure of the amount of space an object takes up or can hold. Measuring Volume of Liquid: - A graduated cylinder is used to measure the volume of liquid. How to read/measure volume of liquid: 1) Learn the scale of the graduated cylinder to learn how many milliliters each measuring line represents – look at two sequential numbers, subtract one from the other to get the difference, divide this difference by number of lines between these two numbers. 1 2) Get eye level with the curved surface of the water (this is called the MENISCUS) and read at the bottom of this curve. Measuring Volume of Regular Shaped, cubelike, box type objects: Measure length, width, and height of object and use formula l x w x h to obtain its volume. Measuring Volume of Irregular Shaped objects using Water Displacement Method: 1) Learn the scale of the graduated cylinder to learn how many milliliters each measuring line represents – look at two sequential numbers, subtract one from the other to get the difference, divide this difference by number of lines between these two numbers. 2) Fill graduated cylinder with enough water to more than cover the object. 3) Read this beginning level of water (eye level, read water at bottom of water curve or meniscus). 4) Gently slide/drop object into graduated cylinder so you do not splash water out of cylinder. Losing water would give an inaccurate reading/measurement. 5) Read new level of water (eye level, read water at bottom of water curve or meniscus). 6) Subtract beginning level from new level of water – this is the volume of your object. DENSITY: - Definition - a measure of how much mass is contained in a given volume. - Density is a physical property of matter (like color, shape, size). - All elements, molecules, compounds, substances have a certain density that does not change when their size or shape change. - The density of an object is calculated by dividing its mass by its volume. - Its formula is D = M/V. - An object’s density is expressed as a combination of two units, that of mass and that of volume. Two common units of density are g/ml and g/cm3. - Some density scenarios: Volume remains the same, mass increases, density increases – example is filling up a suitcase Volume remains the same, mass decreases, density decreases – example is emptying the suitcase - Sample density calculation: A metal object has a mass of 57g and a volume of 21 cm3. Its density is calculated as follows: Mass = 57g Volume = 21 cm3 Density = Mass/Volume, so 57g/21cm3 = 2.7g/cm3 DENSITY AND BUOYANCY: - Definition of buoyancy – the ability of an object to float in water or rise in air. - An object’s or substance’s buoyancy depends on its density compared to the density of water. - The density of water is 1.00 g/ml. - An object with a density less than that of water will float. - An object with a density more than that of water will sink. 2