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PHYSICAL SCIENCE. CHAPTER 2 NOTES Mr. Wemhoff. Chapter 2 Notes.
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PHYSICAL SCIENCE CHAPTER 2 NOTES Mr. Wemhoff
Chapter 2 Notes • How were scientists able to measure the distance from the Earth to the Moon? They were able to use mirrors and lasers. They shot a laser at a reflective surface on the moon and then they recorded the time that it took for that laser to return back to the Earth. They know what the speed of light is and they know how long it took for the light to travel then they were able to calculate the distance in which the light traveled. • What is a light year?The distance in which light can travel in one year which is 9.5 trillion kilometers. • The nearest star is 4.2 light years away so how many kilometers away is this star? 39.9 trillion kilometers
Chapter 2 Notes • Time and Temperature • What is time? The interval between two events • How do we measure time in the SI system? In seconds • What do we think of temperature as? How hot or cold something is • In science how do we measure temperature? On the Celsius scale • What is the point of freezing of water on the Celsius scale? 0 degrees • What is the boiling point of water on the Celsius scale? 100 degrees • What is the average human body temp in C? 37 degrees • What is room temp? 20-25 degrees
Chapter 2 Notes • What is the SI unit used for temperature? Kelvin • What is the freezing point of water in the Kelvin scale? 273 degrees • What is the boiling point of water IN THE Kelvin scale? 373 degrees • What does zero mean on the Kelvin scale? Absolute zero • What is absolute zero? The coldest possible temperature that anything can get. • How do the Kelvin and the Celsius temperature scale correlate with each other?The Kelvin temp. Can be found by adding 273 to the temp. of the Celsius reading.
Chapter 2 Notes • Section 2.3 Graphing • What is the purpose of a graph? To display visually information or data • What are the three types of graphs that are commonly used? Line, bar and circle. • Line = Change over time • Bar = Compares amounts • Circle/pie = Percentages • What can a graph show us? A change between two variables.
Chapter 2 Notes • What is the SI system based on? The powers of ten • How to work with the metric system = • Prefix Multiplying - Factor • Kilo- 1000 • Hecta- 100 • Deca- 10 • Units = meter, liter, gram =1 • deci- .1 • centi- .01 • milli- .001
Chapter 2 Notes • When we try to convert measurements to another unit we have to use multiples of ten. When we start with 1 meter that is the unit between deca- and deci- sort of like a base. • Say we want to find out how many kilometers there are in a meter, what steps do we have to follow? • 1.0m and we want Km. How many places will we have to move the decimal how many places? 3 • We know that we have to move the decimal over three spots but which direction do we have to move it? To the left
Chapter 2 Notes • Ex. if you have a measurement of 25 meters and you want to find out how many centimeters there are in that distance what will you have to do? How many decimal places will you have to move? Which direction will you have to move the decimal? • You need to move it over two places and to the right. 2500 cm • How many millimeters will there be in 25 meters? 25000 mm • How many kilometers are there in 25 meters? .025 Km
Chapter 2 Notes • Does this system work just for distance?No, it also works for mass (grams) and volume (liters). • If I were trying to find out how many Liters there were in 34.56 milliliters how many would there be? • Which way would we have to move the decimal? • To the left because the unit you want to find is larger than the one you have. • How many places will you have to move the decimal over? Three • What would be you answer? .03456 L
Chapter 2 Notes • If you have 278 kilograms and you want to know how many milligrams you would have which way would you have to move the decimal?To the right • How many places would you have to move the decimal? 6 • What would be your answer? 278,000,000 mg
Chapter 2 Notes • Try doing these examples on your own • 45 cm = __________Km • 37.12 mL = _________L • 894.23 mg = ___________g • .8764 kL = ___________L • 5629 km = ___________ m • .7564m = ___________cm • 3.245 g = ___________ mg
Answers to Conversion Problems • .00045 Km • .03712 L • .89423 g • 876.4 L • 5629000 m • 75.64 cm • 3245 mg