![]() ![]() This phenomenon is caused by the fact that water molecules are more attracted to glass than to each other (adhesive forces are stronger than cohesive forces). Look in the textbook for a picture of a graduated cylinder.įirst, note that the surface of the liquid is curved. So, How many significant figures does our volume of 47 1 mL have? Answer - 2! The "4" we know for sure plus the "7" we had to estimate. All the answers are correct within the reading error of 1 mL. You might have read 46 mL your friend might read the volume as 48 mL. The volume we read from the beaker has a reading error of 1 mL. The smallest division is 10 mL, so we can read the volume to 1/10 of 10 mL or 1 mL. If you are less sure of yourself, you can read to 1/5 or 0.2 of the smallest division. (This rule applies to any measurement.) This means that the error in reading (called the reading error) is 1/10 or 0.1 of the smallest division on the glassware. Recall: the number of significant figures includes one estimated digit.Ī rule of thumb: read the volume to 1/10 or 0.1 of the smallest division. This will give us the number of figures that are significant. Which glassware would give you the most precise volume measurement? Let's figure out the volume for each one and its associated error. ![]() a beaker with volumes marked on the side,.Let's look at an example where significant figures is important : measuring volume in the laboratory. So, does the concept of significant figures deal with precision or accuracy? I'll answer this question after you peruse the next example. The number of significant figures is the number of digits believed to be correct by the person doing the measuring. In any measurement, the number of significant figures is critical. Precision refers to how closely individual measurements agree with each other. An even more precise measurement would be 215.6 mm (4 significant figures).Īccuracy refers to how closely a measured value agrees with the correct value. ![]() If I am more precise, I might get 216 mm (3 significant figures). If I quickly measure the width of a piece of notebook paper, I might get 220 mm (2 significant figures). example: Most people have exactly 10 fingers and 10 toes.example: There are exactly 12 eggs in a dozen.There are two kinds of numbers in the world : ![]()
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