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Chemistry

Chemistry. Chapter 4: What’s the Matter?. Concept Attainment Activity. States of Matter. There are three familiar states ( phases ) of matter: solid : has a definite volume and shape (unless in small pieces, eg. sand) liquid : has a definite volume, but shape depends on its container

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Chemistry

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  1. Chemistry Chapter 4: What’s the Matter?

  2. Concept Attainment Activity

  3. States of Matter There are three familiar states (phases) of matter: • solid: has a definite volume and shape (unless in small pieces, eg. sand) • liquid: has a definite volume, but shape depends on its container • gas: volume and shape are determined by surroundings

  4. 4.1 – Properties • Property: A characteristic used to identify a substance. Properties are observed! • There are two types of properties: • Qualitative Properties are properties you can observe with the five senses • Quantitative Properties are properties that you can observe by taking a measurement or simple test

  5. Describing Qualitative Properties:

  6. Measuring Quantitative Properties

  7. Most substances have two temperatures at which they change state: • Melting Point • Temperature at which a solid changes into a liquid • Freezing Point • Temperature at which a liquid changes into a solid • Freezing and melting happen at the same temperature! • Example: water freezes at 0˚ but also melts at 0˚) • Boiling Point • Temperature at which a liquid changes into a gas Melting points and boiling are properties that can help identify a substance.

  8. Plasma • A gas that has electricity running through it. • Sometimes called the 4th state of matter • Found in nebulas, stars and the northern lights • Found in TVs, Neon Lights and Fluorescent lights • Watch this video

  9. 4.3 Mass and Volume • Everything in the Universe is made of matter or Energy • Matter is made up of particles called atoms and molecules. • It is anything that has a mass and occupies space.

  10. MASS: a measurement of the amount of matter in an object. • WEIGHT: the force of gravity pulling on an object. • Mass is the same everywhere in the universe but weight will change depending on the force of gravity. http://www.exploratorium.edu/ronh/weight/

  11. Metric Units • Very small masses are measured in milligrams (mg) • milli means 1/1000 • Small masses in grams (g) • Large masses in kilograms (kg) • kilo means 1000 1 mg = 1/1000 g and 1 kg= 1000 g

  12. How can we convert between mg, g, kg? mg  g: divide by 1000 • (or move the decimal place 3 places to the left) g  mg: multiply by 1000 • (or move the decimal place 3 places to the right) g  kg: divide by 1000 • (or move the decimal place 3 places to the left) kg  g: multiply by 1000 • (or move the decimal pace 3 places to the right)

  13. Measuring Mass – A Quantitative Property • Direct Measurement: a measurement that takes one step. • When you can put an object right on a scale • Indirect measurement: a measurement that takes multiple steps • When you have to put the object in a container on a scale

  14. Measuring Mass – A Quantitative Property To find mass indirectly, you need to put the object in a container. Example: finding the mass of sand or water. Mass of water = 30 g (mass of container + substance) – ( mass of container) 50 g – 20 g = 30g

  15. Measuring Volume – A Quantitative Property • Volume: a measure of the amount of space that is occupied by matter.

  16. Metric Units • Volume of a solid is usually give in cm3 • Volume of a liquid in mL or L 1 cm3 = 1 mL and 1000 cm3 =1L cm3 mL Liters (L)

  17. How can we convert between mL, and L? mL  L: divide by 1000 • (or move the decimal place 3 places to the left) L  mL: multiply by 1000 • (or move the decimal place 3 places to the right)

  18. Measuring Volume – A Quantitative Property There are many different ways to measure volume. • Graduated Cylinder • Used with liquids • Always measure below the Meniscus • Make sure that your eye is level with the meniscus

  19. http://www.taw.org.uk/lic/itp/itps/measuringCylinder_1_2.swf

  20. Mathematically • Volume of a Rectangular solid Volume= length x height x width =4cm x 2cm x 3cm = 24 cm3

  21. Displacement Method • Irregular Solids V of object= (V of water + object) – V of water Ex) When a stone is dropped into a graduated cylinder filled with 10mL water, the water raises to 35mL. What is the volume of the object? 35mL – 10 mL = 25mL http://www.taw.org.uk/lic/itp/itps/measuringCylinder_1_2.swf

  22. Measuring Volume – A Quantitative Property • Direct Measurement: a measurement that takes one step. • Using a graduated cylinder or mathematically calculating volume are direct methods of measurement. • Indirect measurement: a measurement that takes multiple steps • The displacement method is an indirect method of measurement.

  23. Calculating Density 4.5 • Why does oil float on water? • Because it is less dense than water! • What is density? Density is the mass per unit volume of a substance Density is a quantitative property

  24. Density can be calculated using a formula. D= m/V Density is expressed in g/cm3 and g/mL

  25. Each substance has its own unique density (see Table 1 page 109) • Water has a density of 1.00 g/ml A substance will float in water if is has a density less than 1.00 g/ml A substance will sink in water if is has a density greater than 1.00 g/ml

  26. If you mix crude oil and water, which will sink and which will float? Why? The density of crude oil is 0.86 – 0.88 g/mL The density of water is 1.00g/mL The oil will float because it is less dense than water.

  27. Comparing Densities Birch wood has a density of 0.66 g/cm3 (in other words 0.66 g/mL) which means that every cubic cm of birch wood has a mass of 0.66 g Will birch float or sink in water?  Birch will float when placed in water since its density (0.66 g/cm3) is less than that of water (1.00 g/mL)

  28. Comparing Densities Will a piece of iron sink or float in water? The density of iron is 7.87 g/cm3 ? Sink because its density is more than that of water (1.00 g/mL) If water (D = 1.00 g/mL), rubbing alcohol (D = 0.79 g/mL) and vegetable oil (D = 0.92 g/mL) were all placed in a container, in what order would you expect to settle out? List them from top to bottom.

  29. Comparing Densities The rubbing alcohol would be the toplayer since it’s the least dense and would therefore float on top of the other substances. The vegetable oil would form a middle layer since it would sink below the alcohol but float on the water. The water would form a bottom layer since it has the highest density so would sink in the other substances.

  30. Examples Calculate the density of a substance with a mass of 340 g and a volume of 811 mL D= m/V = 340g / 811 mL = 0.42 g/ mL

  31. Calculating Density A block of fir measures 240 cm3. If its mass is 144 g, find the density of the wood. D = m / V D = 144 / 240 D = 0.6 g/cm3

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