Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Unit 1 B -Chapter 2 Density % Error Precise vs. Accurate Properties of Matter Matter and Change

What is Density? What determines the density of a substance?

Density is…. a physical property of a substance that can be used for identification a relationship between the mass of the substance and how much space it takes up (volume). the amount of atoms and how they are arranged determines the density of a substance.

Which one is more dense? Solid - Liquid - Gas - Draw the arrangement of molecules for...

Density Equation Density equals the mass of the substance divided by its volume; EQUATION Objects with the same volume but different masses have different densities. Objects with different volumes but the same mass have different densities. Objects with the same volume and the same mass have the same density.

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. This figure compares the density of four substances: lithium, water, aluminum, and lead. Increasing density (mass per unit volume) 10.g 0.53 g/cm 3 19 cm 3 10.g 10. cm 3 10.g 3.7cm 3 10.g 0.88cm g/cm g/cm 3 11 g/cm 3

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Because of differences in density, liquids separate into layers. As shown at right, corn oil floats on top of water because it is less dense. Corn syrup sinks below water because it is more dense. Density Corn oil Water Corn syrup

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Interpret Data Densities of Some Common Materials Solids and LiquidsGases Material Density at 20°C (g/cm 3 ) Material Density at 20°C (g/L) Gold19.3Chlorine2.95 Mercury13.6Carbon dioxide1.83 Lead11.3Argon1.66 Aluminum2.70Oxygen1.33 Table sugar1.59Air1.20 Corn syrup 1.35 – 1.38 Nitrogen1.17 Water (4°C)1.000Neon0.84 Corn oil0.922Ammonia0.718 Ice (0°C)0.917Methane0.665 Ethanol0.789Helium0.166 Gasoline 0.66 – 0.69 Hydrogen0.084

Sample Problems Sample Problem 1. The mass of a 8.0 cm 3 block of wood is 6.33 g, find its density

Sample Problems Sample Problem 2. Find the density of an unknown object that has a mass of g and a volume of 12.5 cm 3. Then, use the density to identify the substance. Densities of Some Common Materials Solids and LiquidsGases Material Density at 20°C (g/cm 3 ) Material Density at 20°C (g/L) Gold19.3Chlorine2.95 Mercury13.6Carbon dioxide1.83 Lead11.3Argon1.66 Aluminum2.70Oxygen1.33 Table sugar1.59Air1.20 Corn syrup 1.35 – 1.38 Nitrogen1.17 Water (4°C)1.000Neon0.84 Corn oil0.922Ammonia0.718 Ice (0°C)0.917Methane0.665 Ethanol0.789Helium0.166 Gasoline 0.66 – 0.69 Hydrogen0.084

Calculating Mass or Volume from Density Sample Problem 1. What would be the volume of 5.16 g of gold? Densities of Some Common Materials Solids and LiquidsGases Material Density at 20°C (g/cm 3 ) Material Density at 20°C (g/L) Gold19.3Chlorine2.95 Mercury13.6Carbon dioxide1.83 Lead11.3Argon1.66 Aluminum2.70Oxygen1.33 Table sugar1.59Air1.20 Corn syrup 1.35 – 1.38 Nitrogen1.17 Water (4°C)1.000Neon0.84 Corn oil0.922Ammonia0.718 Ice (0°C)0.917Methane0.665 Ethanol0.789Helium0.166 Gasoline 0.66 – 0.69 Hydrogen0.084

Calculating Mass or Volume from Density Densities of Some Common Materials Solids and LiquidsGases Material Density at 20°C (g/cm 3 ) Material Density at 20°C (g/L) Gold19.3Chlorine2.95 Mercury13.6Carbon dioxide1.83 Lead11.3Argon1.66 Aluminum2.70Oxygen1.33 Table sugar1.59Air1.20 Corn syrup 1.35 – 1.38 Nitrogen1.17 Water (4°C)1.000Neon0.84 Corn oil0.922Ammonia0.718 Ice (0°C)0.917Methane0.665 Ethanol0.789Helium0.166 Gasoline 0.66 – 0.69 Hydrogen0.084 Sample Problem 2. What would be the mass of 32 cm 3 of lead?

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Can you assume that something with a low weight will float in water? No, it is the relationship between an object’s mass and its volume, its density, that tells you whether it will float or sink.

End Notes -Density Start Notes - % Error and

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Accuracy, Precision, and Error How do you evaluate accuracy and precision?

Accuracy vs. Precision Accuracy is a measure of how close a measurement comes to the actual or true value of whatever is measured Precision is a measure of how close a series of measurements are to one another, irrespective of the actual value.

Video Clip: Accuracy vs Precision

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Suppose you use a thermometer to measure the boiling point of pure water at standard pressure. The thermometer reads 99.1°C. You probably know that the true or accepted value of the boiling point of pure water at these conditions is actually 100.0°C. Determining Error

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. There is a difference between the accepted value, which is the correct value for the measurement based on reliable references, and the experimental value, the value measured in the lab. The difference between the experimental value and the accepted value is called the error. Determining Error Error = experimental value – accepted value

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Error can be positive or negative, depending on whether the experimental value is greater than or less than the accepted value. For the boiling-point measurement, the error is 99.1°C – 100°C = –0.9°C error For a boiling point measurement of °C, the error is – 100 = 0.9°C error Determining Error

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. The percent error of a measurement is the absolute value of the error divided by the accepted value, multiplied by 100%. Determining Error x Percent Error = Error Accepted Value x 100% experimental - accepted x 100%

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Calculating Percent Error The boiling point of pure ethanol is measured to be 77.1°C. Calculate the percent error if the accepted value is for ethanol 78.4°C. Think about it: Using the absolute value of the error means that percent error will always be a positive value.

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Calculate Solve for the unknown. Substitute the equation for error, and then plug in the known values. Percent error = |experimental value – accepted value| _______________________________ accepted value X 100 _______ = 78.4°C X 100 % = 1.66% 1.3°C |77.1°C – 78.4°C| X 100= 78.4°C

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Evaluate Does the result make sense? The experimental value was off by about 1°C, or 1/78th of the accepted value (78.4°C). The answer makes sense.

Calculating Percent Error 1 You measure the dimensions of an Aluminum block and then determine the mass. Using that information you calculate the density of the block to be 2.79 g/cm 3. You look up the density of aluminum to be 2.70 g/cm 3. Calculate the % error.

End Notes % Error Start Notes - Properties and Changes

Physical vs. Chemical Properties

Activate your Prior Knowledge: Compile a list of properties of any substance, what could you observe or measure? List at least 5 different properties and label as Physical or Chemical

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. A physical property is a quality or condition of a substance that can be observed or measured without changing the substance’s composition. A chemical property is a quality or condition that gives matter the ability to undergo a change that alters its composition Two different types of properties

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Absorbency Conductivity Malleability Color Odor State of Matter examples of properties Reactivity Flammability Toxicity Oxidizing Radioactivity Combustibility

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Absorbency Conductivity Malleability Color Odor State of Matter Examples of properties Reactivity Flammability Toxicity Oxidizing Radioactivity Combustibility Physical propertiesChemical properties

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Every sample of a given substance has identical properties because every sample has the same composition. Identifying a Substance Describing Matter

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Glass is often used to make windows, while copper is often used in electrical wires. What properties of glass make it a desirable material to use for windows? CHEMISTRY & YOU

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Glass is often used to make windows, while copper is often used in electrical wires. What properties of glass make it a desirable material to use for windows? Glass is transparent, so it can be seen through; hard, so it stays in place within window frames; and heat resistant, so it helps prevent the transfer of heat between outside and inside. CHEMISTRY & YOU

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Physical properties can help chemists identify substances. For example, a colorless substance that was found to boil at 100˚C and melt at 0˚C would likely be water. A colorless substance that boiled at 78˚C and melted at –117˚C would definitely not be water. It would likely be ethanol. Identifying a Substance Describing Matter

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Physical Properties of Some Substances SubstanceStateColorMelting point (°C)Boiling point (°C) NeonGasColorless–249–246 OxygenGasColorless–218–183 ChlorineGasGreenish-yellow–101 –34 EthanolLiquidColorless– MercuryLiquidSilvery-white – BromineLiquidReddish-brown –7 59 WaterLiquidColorless SulfurSolidYellow Sodium chlorideSolidWhite GoldSolidYellow CopperSolidReddish-yellow Interpret Data This table lists physical properties for some substances. The states of the substances are given at room temperature.

Physical vs. Chemical Change

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. In this lesson, you will learn to recognize whether the burning match is a chemical change or physical change. CHEMISTRY & YOU What happened to the match?

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. When a change occurs to a substance, it can be either a Physical Change or a Chemical Change. What do you think is the difference?

PhysicalChange Some properties of a material change, but the composition of the material does not change. Change Chemical Change One or more new substances are created The composition of matter always changes. It has properties that are different from starting materials You cannot get original materials back

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. The melting point of gallium metal is 30˚C. The figure at left shows how the heat from a person’s hand can melt a sample of gallium. gallium Physical Changes

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. The shape of the sample changes during melting as the liquid begins to flow, but the composition of the sample does not change. Melting is a physical change. Physical Changes

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Words such as boil, freeze, melt, and condense are used to describe physical changes. So are words such as break, split, grind, cut, and crush. Physical Changes

Ice → Water → Steam (They are all water) Paper cut into pieces is still paper Cutting wood into pieces is still wood Molding a sculpture is still cement or marble Physical Changes

Chemical Changes

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Words such as burn, rot, rust, decompose, ferment, explode, and corrode usually signify a chemical change. The ability of a substance to undergo a specific chemical change is called a chemical property. Chemical Changes

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Iron is able to combine with oxygen to form rust. The ability to rust is a chemical property of iron. Chemical properties can be used to identify a substance. Chemical properties can be observed only when a substance undergoes a chemical change. Chemical Changes

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Recognizing Chemical Changes What always happens during a chemical change? Chemical Changes

Use 'FARTS' as a way for you to remember when a chemical reaction occurs:

Change of odor. Change of color (for example, silver to reddish-brown when iron rusts).iron Change in temperature or energy, such as the production (exothermic) or loss (endothermic) of heat.energyexothermicendothermicheat Change of composition - paper turning to ash when burned. LightLight and/or heat given off.heat Formation of gases, often appearing as bubbles in liquids. Formation of a precipitate (insoluble particles).precipitate The decomposition of organic matter (for example, rotting food).organic matter The change is difficult or impossible to reverse. Chemical Changes

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.. Boiling Melting Breaking Cutting Crushing Dissolving Examples of Changes Rotting Rusting/Oxidizing Burning Souring Decomposing Physical Change Chemical Change

Recognizing Chemical Changes DEMO Recognizing Chemical Changes p49 of teacher text book.

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