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Metric System Quantity Measured Length Unit Symbol Meter m Mass Kilogram kg Time Second s Volume Liter L Temperature Kelvin K Metric Prefixes Prefix Symbol Multiplying factor(x base unit) Kilo- k 1000 Hecto- h 100 Deka- dk (or da) 10 Base unit 1 Deci- d 0.1 Centi- c 0.01 Milli- m 0.001 Something to help you convert: Examples 100 km to m 100 mm to m King Henry Died By Drinking Chocolate Milk (Where B stands for Basic Unit) How do you use the “steps” Decide what unit (prefix, first letter) you are currently in, put a star under that step. Decide which unit you are going to, put a dot under that step. Put your pencil on the star and decide how many steps you have to move, and in which direction, to reach the dot. Put your pencil on the decimal of your number and move it the same number of places in the same direction you determined in the previous step. Examples: 1. How many cm are in a 45m long piece of wood? 2. How many L will a 290mL sample of liquid contain? 3. A runner won a race by 4ms, how many ds will that be? 4. Fred needs to measure 2km of rope. His ruler can only measure in cm. How many cm should he measure? 2 ways to find the volume of object: If the dimensions are given then multiply length x width x height in cm. (for regularshaped objects: cube or rectangular prism) If the volume is determined by water displacement take the difference between the volume with the object and the volume without the object. (for irregular-shaped objects) Volume Remember in math when you could find volume by multiplying length times width times height? Some more examples: A pharmacist must measure out 0.275L of water to mix a bottle of medication. He has a cup that measures in cm3 (in the medical field they call these cc’s which stands for cubic centimeters). How many cm3 must he measure out to have 0.275L of water? How many dm3 are in 300mL? Temperature In metric, we start with a Celsius thermometer. Water boils at 100oC and freezes at 0oC. If you look back, the metric unit for temperature is Kelvin. To convert from Celsius to Kelvin, just add 273 to your Celsius temperature. Temperature examples problems: 1. The temperature of a classroom is determined to be 20oC. What is the temperature in Kelvin? 2. The temperature of liquid nitrogen is 70K. What is this temperature in Celsius? Density Density is how much mass is in a given volume of a substance. Units for density Density has a derived unit. It isn’t just one unit, but a combination of units. Some Density examples: 1. A block of metal is 5cm long, 2 cm wide and 1 cm tall. It is placed on a scale and determined to have a mass of 595g. What is the density of this metal? 2. What is the mass of a 25mL sample of aluminum if it has a density of 2.7g/mL? 3. What volume will a 300g sample of gold occupy if the density of gold is 19.3g/cm3? Some more Density 1. A 4g sample of plastic is placed into a graduated cylinder which contains 10mL of water. After the plastic is in the water the level reaches 15mL. What is the density of the plastic? 2. A marble is placed on a balance and has a mass of 3g. Then the marble is placed into 9mL of water and the level goes up to 11mL. What is the density of the marble? Chemical and Physical Properties: Chemical Property: a characteristic that can only be observed or measured by changing the chemical composition of a substance. Physical Property: a characteristic that can be observed or measured without changing the substances composition. Key Question: Does characteristic involve change in composition of substance? If yes, Chemical Property. If no, Physical Property. Examples of Chemical Properties: • Carbon burns in air to form carbon dioxide. • Iron rusts when left out in the rain. • Baking soda bubbles vigorously when vinegar is poured on it. • Sulfur burned in coal makes sulfur trioxide which combines with water in the clouds to make acid rain. * All are observations in which a substances chemical composition is changed. Examples of Physical Properties • • • • Water boils at 100oC. Copper is a good conductor of electricity. Gold has a density of 19.3g/mL Mercury is silver in color and a liquid at room temperature. • Oxygen is a gas at room temperature. • Motor oil comes in different viscosities. * All are observations (size, shape, color, odor, or phase) where the chemical composition is not changed. Can you pick out which property is chemical and which is physical? 1. Hydrogen will burn in oxygen to make water vapor. 2. Sodium chloride is a white solid at room temperature. 3. Mercury has a density of 13.5g/mL 4. Copper forms a deep blue solution when it is in contact with ammonia. 5. Oil and vinegar don’t mix. Chemical and Physical Change Chemical change: a process that involves one or more substances changing into new substances (i.e. chemical composition has changed). Physical change: a change in state or condition without changing into another substance or altering chemical composition. Examples of Chemical Change • Burning (exploding) • Rusting (oxidizing, corroding, tarnishing) • Bubbles • Color change • Decomposing *All are processes that involve a change in chemical composition. Example of Physical Change • Melting, boiling, freezing, condensing, sublimation. • Draw metal into a wire, roll it into a sheet, etc. • Cut up. *All are processes that do not involve a change in chemical composition. There are only changes in size, shape, or phase. Chemical Property vs. Chemical Change. Confused? • Inevitably, you cannot define chemical property without change. – Ex: Carbon burns in air to form carbon dioxide. The fact that carbon burns is its chemical property (you observe this). Carbon burning and producing carbon dioxide is the chemical change. Can you tell which change is chemical and physical 1) The Copper on a statue oxidizes making a green color. 2) A student finds a piece of wax melted on the counter top. 3) A log is burning in a fireplace. 4) Your mom used her good silver serving spoon to serve eggs and it tarnished. 5) The outside of your glass of sweet tea is all wet on a humid day. Chemical Reactions and Energy Some reactions need energy in order to happen. These are ENDOTHERMIC reactions. They get colder as they react. Bond breaking Bond making Some reactions give off energy as a product of the reaction. These are EXOTHERMIC reactions. They get hotter as they react. Which is Exo and which is Endo? 1. A chemical is poured on the counter and lit on fire and it gets so hot the sprinkler system goes off. 2. A plastic bag with chemicals is used for an injured athlete. The student trainer breaks something inside the bag and shakes it. It gets cold and can be used on the injured athlete.