Properties of Matter Physical & Chemical Changes

Physical Properties Physical properties are observable Physical properties are observable Examples are: Examples are: Mass Mass Volume Volume Density Density Melting point Melting point Boiling point Boiling point Hardness Hardness Ability to conduct electricity Ability to conduct electricity Physical State – solid, liquid, or gas Physical State – solid, liquid, or gas

Physical Properties Help ID Substances! A physical property can be used to identify a substance – shape, color, odor, texture A physical property can be used to identify a substance – shape, color, odor, texture Example: What is… Example: What is… Round Round Orange Orange Smells rubbery Smells rubbery Bounces Bounces A Basketball!! A Basketball!!

Magic Eggs Demo Observe what happens to the two eggs…. Observe what happens to the two eggs…. What physical property caused one to float and one to sink? What physical property caused one to float and one to sink?

What is Density? Density is a measure of how much “stuff” is contained in a certain volume of a substance. Density is a measure of how much “stuff” is contained in a certain volume of a substance. A low density item is “light” in comparison to something else of the same volume A low density item is “light” in comparison to something else of the same volume Which is more dense? A or B? Which is more dense? A or B? Answer: B – there is more “Stuff” for the same volume! Answer: B – there is more “Stuff” for the same volume! A B

Online Lab Go to the website, click on Online Density Lab and fill out the corresponding worksheet. Go to the website, click on Online Density Lab and fill out the corresponding worksheet.

Density Equation D = m/V D = density M = mass V = volume Units! Mass must be in grams Volume may be in either cm 3 (if it is a solid) or mL (if it is a liquid) Density = g/cm 3 or g/mL

Example Problem #1 You are given a cube made out of an unknown substance. How would you determine its density? You are given a cube made out of an unknown substance. How would you determine its density? First you can measure one side – let’s say it is 2cm. First you can measure one side – let’s say it is 2cm. Volume = l x w x h Volume = l x w x h 2 x 2 x 2 = 8 cm 3 2 x 2 x 2 = 8 cm 3 Then you can weigh it on a scale – let’s say its mass is 240 g Then you can weigh it on a scale – let’s say its mass is 240 g D = m/V D = 240g/8cm 3 D = 30 g/cm 3

Example Problem #2 You are given a cylinder made of an unknown substance. How would you determine its density? You are given a cylinder made of an unknown substance. How would you determine its density? To find the volume you can drop it in a cylinder of water and note the change in volume – let’s say the water level rises 10 mL To find the volume you can drop it in a cylinder of water and note the change in volume – let’s say the water level rises 10 mL Then you can weigh it on a scale – let’s say the mass is 100g Then you can weigh it on a scale – let’s say the mass is 100g D = m/V D = 100g/10mL D = 10 g/mL

Float or Sink? Density determines whether an object will float or sink. Density determines whether an object will float or sink. If an object is less dense than the fluid it is immersed in, it will float If an object is less dense than the fluid it is immersed in, it will float If it is more dense, it will sink If it is more dense, it will sink Demos: Demos:

Review Give four examples of a physical property. Give four examples of a physical property. What is density? What is density? Remember that density is a physical property and is unique to the matter – copper will have the same density, no matter how big or small the object is. Remember that density is a physical property and is unique to the matter – copper will have the same density, no matter how big or small the object is. How do you find volume if the object is a cube? A cylinder (round object)? How do you find volume if the object is a cube? A cylinder (round object)? Time to practice using the density equation…. Time to practice using the density equation….

Time for Labs!! Cylinder Lab Cylinder Lab Density Challenge Density Challenge Density Challenge #2 Density Challenge #2

Chemical Properties Chemical properties are related to the elements that make up a substance. Chemical properties are related to the elements that make up a substance. They are not as easy to observe a physical properties They are not as easy to observe a physical properties Examples: Examples: Flammability Flammability Reactivity Reactivity

Physical vs. Chemical Properties Physical properties are readily observable Physical properties are readily observable Chemical properties can only be observed as the object is changing Chemical properties can only be observed as the object is changing Example – you do not know if an object is flammable until you set it on fire! Example – you do not know if an object is flammable until you set it on fire!

Physical vs. Chemical Properties Baking Soda White Powder Reacts with Vinegar Rubbing Alcohol Clear Liquid Flammable Red Food Coloring Red Color Reacts with Bleach to lose its Color IronMalleable Reacts with Oxygen Physical PropertiesChemical Properties

Changes of Matter Physical Change Physical Change Affects one or more physical property, but does NOT change the identity of the substance Affects one or more physical property, but does NOT change the identity of the substance Break a piece of chalk – it is still chalk! Break a piece of chalk – it is still chalk! Chemical Change Chemical Change The substance changes into an entirely new substance with different properties The substance changes into an entirely new substance with different properties Not reversible (except by another chemical reaction) Not reversible (except by another chemical reaction) Bake a cake – the cake is entirely different from the batter – new properties! Bake a cake – the cake is entirely different from the batter – new properties!

Physical or Chemical Change? Cutting Your Hair Rusting Boiling Water Dissolving Salt in Water Burning Wood Frying an Egg Physical Chemical

OK – one more Lab….