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## Do Now! September 25, 2012

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**Do Now!September 25, 2012**Another T-chart!!!!!!!!!!!!! It’s the last one…. For now. • Which are physical properties? • Which are chemical properties? Temperature Color Tarnish (think jewlery) Melting Point Odor Hardness Rusting Amount Combustion (think gasoline) THEN… Work on the Ch. 13 Sec. 1 ASSESSMENT QUESTIONS pg. 545**Physical Properties**Chemical Properties**WednesdaySeptember 26, 2012**Fe2O3 What is the ratio of atoms of iron (Fe) to atoms of oxygen (O) in this compound? Iron to oxygen is ____ to _____ Iron:oxygen = _____:____ What about for the compound AlCl3? What is the compound and what is the ratio of atoms?**ThursdaySeptember 27, 2012**Find the volume of your science textbook and of another object at your desk (of your choosing). List ALL steps on your Do Now page. Rulers are on my desk.**Do the following problems:*Remember!* write every step of**the problem!! V = L x W x H D = m/VWhat is the density of a piece of wood that has a mass of 25.0 grams and a volume of 29.4 cm3? The density of water is 1 g/cm3. A piece of wood that measures 3.0 cm by 6.0 cm by 4.0 cm has a mass of 80.0 grams. What is the density of the wood? Would the piece of wood float in water? (volume = L x W x H)**What is the density of a piece of wood that has a mass of**25.0 grams and a volume of 29.4 cm3?**A piece of wood that measures 3.0 cm by 6.0 cm by 4.0 cm**has a mass of 80.0 grams. What is the density of the wood? Would the piece of wood float in water? (volume = L x W x H)**I threw a plastic ball in the pool for my dog to fetch. The**mass of the ball was 125 grams. What must the volume be to have a density of 0.500 g/mL. ( I want it to float of course!)**Measuring Matter**Chapter 13 Section 2**Discuss(by raising your hands, people)**How do we measure matter? What do we use to measure matter? What is the difference between weight and mass?**A riddle…**Which weighs more, a pound of feathers, or a pound of sand? ….. They weigh the same! One pound!**Weight & Mass**• Suppose you want to measure your weight. • As you step on a scale, your body weight presses down on the springs inside. • The more you weigh, the more the springs compress, causing the pointer on the scale to turn farther, giving a higher reading. • If you took this exact scale to the moon, would it indicate the same weight?**Weight**Your weight is a measure of the force of gravity on you. On Earth, all objects are attracted toward the center of the planet by the force of Earth’s gravity.**Mass**The mass of an object is the measurement of the amount of matter in the object. If you travel to the moon, the amount of matter in your body – your mass – does not change.**? ? ?**Does anyone know why the moon has such a small gravitational pull? Because…………. the mass of the moon is so much smaller than the mass of the Earth! Because of this, the moon exerts much less gravitational force on you.**Units of Mass**To measure the properties of matter, scientists use a system called the International System of Units. Also known as… “SI” (because of its French name, Système International)**Units**The SI unit of mass is the kilogram (kg). If you weigh 90 pounds on Earth, your mass is about 40 kilograms. A smaller unit that is also used is the gram (g). How many grams are in a kilogram? 1000**Why do scientists prefer to describe matter by its mass?**Unlike weight, mass does not change with location, even when the force of gravity on an object changes.**Volume**All matter has mass and takes up space… right? RIGHT! The actual amount of space that matter occupies is called its volume.**Units of Volume**Common units of volume include… *liter (L) *milliliter (mL) *cubic centimeter (cm3)**Calculating Volume**Volume of solid objects = cubic centimeters (cm3) [usually] Volume = Length x Width x Height What is the volume of this brick? 5 cm 20 cm 900 cm3 9 cm**How could you measure the volume of an apple?**Submerge the apple in water in a graduated cylinder. The water level will rise by an amount that is equal to the volume of the object in milliliters.**Density**• Samples of two different materials may have the same volume, but they don’t necessarily have the same mass. A kilogram of sand takes up much less space than a kilogram of feathers. The volumes differ because sand and feathers have different densities.**Density relates the mass of a material in a given volume.**This is often expressed as the number of grams in one cubic centimeter. For example, the density of water at room temperature is expressed as “one gram per cubic centimeter (cm3).” Every gram of water has a volume of 1 cm3**Math in Science?!**Density = mass . This bar (between the ‘g’ and the ‘cm3’) tells you that you can determine the density of a sample of matter by dividing its mass by its volume 1 g/cm3 volume**Sinking or Floating?**Imagine you have a solid block of wood and a solid block of iron. You drop both into a tub of water. Do they float? Do they sink? What happens? Wood floats! (think of a boat…) Iron sinks! (think of an anchor…)**greater**Objects with _______________ densities than water will sink. Objects with _______________ densities than water will float. lesser**Using Density**Density is a _____________ property of a substance. (physical or chemical??) Because of this, density can be used to __________ an ____________substance. physical identify unknown**Imagine you are out hiking, and you find a shiny,**golden-colored rock. How would you know the rock is gold or fool’s gold? • Look up the _________________ of gold. • Measure the ________________ and __________________ of the rock to find its ________________. • If the ______________ matches the amount that you looked up, you have a match!**Happy October!Monday October 1, 2012**• Calculate your weight as it would be on the moon. • Your weight would be only one sixth (.167) of your weight on Earth.