Measuring Length. How do you find the length of an object? Reading the meter scale correctly. Stop and think. Materials

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1 Measuring Length How do you find the length of an object? Size matters! When you describe the length of an object, or the distance between two objects, you are describing something very important about the object. Is it as small as a bacteria (2 micrometers)? Is it a light year away ( meters)? By using the metric system you can quickly see the difference in size between objects. Materials Metric ruler Pencil Paper Small objects Calculator A Reading the meter scale correctly Look at the ruler in the picture above. Each small line on the top of the ruler represents one millimeter. Larger lines stand for 5 millimeter and 10 millimeter intervals. When the object you are measuring falls between the lines, read the number to the nearest 0.5 millimeter. Practice measuring several objects with your own metric ruler. Compare your results with a lab partner. B Stop and think a. You may have seen a ruler like this marked in centimeter units. How many millimeters are in one centimeter? b. Notice that the ruler also has markings for reading the English system. Give an example of when it would be better to measure with the English system than the metric system. Give a different example of when it would be better to use the metric system. 119

2 C Example 1: Measuring objects correctly Look at the picture above. How long is the building block? 1. Report the length of the building block to the nearest 0.5 millimeters. 2. Convert your answer to centimeters. 3. Convert your answer to meters. 120

3 D Example 2: Measuring objects correctly Look at the picture above. How long is the pencil? 1. Report the length of the pencil to the nearest 0.5 millimeters. 2. Challenge: How many building blocks in example 1 will it take to equal the length of the pencil? 3. Challenge: Convert the length of the pencil to inches by dividing your answer by 25.4 millimeters per inch. E Example 3: Measuring objects correctly Look at the picture above. How long is the domino? 1. Report the length of the domino to the nearest 0.5 millimeters. 2. Challenge: How many dominoes will fit end to end on the 30 cm ruler? 121

4 F Practice converting units for length By completing the examples above you show that you are familiar with some of the prefixes used in the metric system like milli- and centi-. The table below gives other prefixes you may be less familiar with. Try converting the length of the domino from millimeters into all the other units given in the table. Refer to the multiplication factor this way: 1 kilometer equals 1000 meters millimeters equals 1 meter. 1. How many millimeters are in a kilometer? 1000 millimeters per meter 1000 meters per kilometer = 1,000,000 millimeters per kilometer 2. Fill in the table with your multiplication factor by converting millimeters to the unit given. The first one is done for you millimeters per meter meters per picometer = 10-9 millimeters per picometer 3. Divide the domino s length in millimeters by the number in your multiplication factor column. This is the answer you will put in the last column. Prefix Symbol Multiplication factor Scientific notation in meters Your multiplication factor Your domino length in: pico- p pm nano- n nm micro- μ μm milli m mm centi- c cm deci- d dm deka- da dam hecto- h hm kilo- k km 122

5 Measuring Temperature How do you find the temperature of a substance? There are many different kinds of thermometers used to measure temperature. Can you think of some you find at home? In your classroom you will use a glass immersion thermometer to find the temperature of a liquid. The thermometer contains alcohol with a red dye in it so you can see the alcohol level inside the thermometer. The alcohol level changes depending on the surrounding temperature. You will practice reading the scale on the thermometer and report your readings in degrees Celsius. Materials Alcohol immersion thermometer Beakers Water at different temperatures Ice Safety: Glass thermometers are breakable. Handle them carefully. Overheating the thermometer can cause the alcohol to separate and give incorrect readings. Glass thermometers should be stored horizontally or vertically (never upside down) to prevent alcohol from separating. A Reading the temperature scale correctly Look at the picture at right. See the close-up of the line inside the thermometer on the scale. The tens scale numbers are given. The ones scale appears as lines. Each small line equals 1 degree Celsius. Practice reading the scale from the bottom to the top. One small line above 20 C is read as 21 C. When the level of the alcohol is between two small lines on the scale, report the number to the nearest 0.5 C. B Stop and think a. What number does the large line between 20 C and 30 C equal? Figure out by counting the number of small lines between 20 C and 30 C. b. Give the temperature of the thermometer in the picture above. c. Practice rounding the following temperature values to the nearest 0.5 C: 23.1 C, 29.8 C, 30.0 C, 31.6 C, 31.4 C. d. Water at 0 C and 100 C has different properties. Describe what water looks like at these temperatures. e. What will happen to the level of the alcohol if you hold the thermometer by the bulb? 123