Measuring

Metric Review Gram (mass) Liter (volume) Meter (length) You need to know these prefixes Kilo (1000) Centi (1/100) Mili (1/1000)

Measuring Measurements- comparison of the magnitude of any quantity to a standard value A standard value is called a unit. We use a ruler, a scale, etc. which is built using the standard value as a reference. All measurements must have a number or magnitude AND a unit (g, m, mL, mg, ..)

Measuring No units make a measurement meaningless. He is 64 tall. This could mean he is 64 ins tall, 64 cm tall,64 ft tall etc. Measuring cannot be done perfectly. It depends on The person’s skill The type of measuring instrument.

Measuring with a Ruler Here are two different types of centimeter rulers to measure the length of something.

Measuring with a Ruler Which one would be a more accurate measuring device? The one with the mm lines (known as ticks) So let’s look at the type of lab equipment that can be used to measure the volume of liquids to determine which would be more accurate.

Measuring Volume The choices are: Pipette Beaker Which is more precise?

Measuring Volume Graduated cylinder Erlenmeyer flask Volumetric flask Which is more precise?

Measuring Volume So when you measure the volume of liquids the more accurate would be the graduated cylinders.

Measuring The fineness of the measuring scale is called the least count. It is the smallest scale division. (The smallest unit on the devise.) Example, the ruler with 1cm markings has a least count of 1cm. The ruler with 1mm markings has a least count of 1mm.

Measuring What would be a more precise instrument to use for measuring, one with a big or small least count? small, you can be more sure of the exact measurement

Measuring We estimate one more digit after the least count. So mentally divided each space by 10 to make 10 more divisions between the 2 marks.

Measuring The measurement of the first ruler is 6.4cm. The measurement of the second ruler is 6.39cm. We may not agree on the last value recorded but we should at least agree on every other value.

Smallest scale division Measuring Measurement Estimated Digit Least Count Smallest scale division 203.4 cm 4.07 cm 56.39 cm 70.1 cm 4 ones place ones 7 tenths place tenths 9 tenths place tenths 1 ones place ones

Measuring Draw pictures of each ruler used above. 203.4 cm 202 203 204 205 206

Measuring Draw pictures of each ruler used above. 4.07 cm 3 4 5 6 7

Measuring Draw pictures of each ruler used above. 56.39 cm 54 55 56 57 58

Measuring Draw pictures of each ruler used above. 70.1 cm 68 69 71 70 72

Measuring So now we can see that Science is based on measurements where we estimate the digit after the least count. Math is based on exact numbers based on counting and by definition. In science 5 ≠ 5.0 ≠ 5.00, as it does in math.

Balances In class we will use a quadruple beam balance.

Balances We have 4 levels the top is the hundreds The next level is the tens Next is the ones And last is the decimals

Reading The Balance Measurement Hundreds Tens Ones 2 Decimal Places

Always Zero Your Balance

Reading The Balance Measurement There are no hundreds, so we read this balance we start with 30 grams Then we read the ones (4), and the first decimal (.1) and second decimal place (.14), lastly the estimated place (.144).

What Does this Balance Read? 135.350 g

Remember how to use the ruler. How many decimal places do we record when we read this ruler? TWO 54 55 56 57 58

These are the new balances. First we read the hundreds, then the tens, now we move to the dial and read the ones, the tenths and the hundreds. What does this balance read? 137.95 g

Graduated Cylinder You read the level in a graduated cylinder by reading the bottom of the meniscus.

Graduated Cylinder Graduated Cylinder 52.5 ml What does this graduated cylinder read? 52.5 ml

Graduated Cylinder What does this graduated cylinder read? 6.62 ml