Physical and Chemical Properties of Matter

Physical Properties How would you describe an orange to someone who has never seen one? –Orange in color –Round –Waxy feel to the rind –Juicy –Sweet Each of these is a physical property –Anything that can be observed or measured without changing the matter’s identity

Examples of physical properties Color Shape Odor Mass Volume Magnetism Conducting electricity strength flexability

Physical properties cont’d Some physical properties can help you determine how to use a substance –Ex: whether its magnetic or if it would be strong enough to hold a certain weight Using physical properties every day: –The “smell” test for dirty clothes –Color of fruit to see if its gone bad –Odor of milk to see if it has spoiled

Density Review Density is the amount of matter in a given space (volume) Density is found by dividing the mass of an object by its volume D = m/v The unit for density is a mass unit divided by a unit of volume Ex: g/cm 3 or g/mL or kg/m 3

Physical Changes Physical changes only affect one or more physical properties of matter –Even though its melted, this is still a popsicle You can still get the original substance back if it has gone through a physical change

Chemical Properties Describe matter based on its ability to change into new matter that has different properties Ex: flammability is the ability of a substance to burn –Wood is flammable – when it burns, it turns to ash Ex: Reactivity is the ability of two or more substances to combine and form one or more new substances

What’s the difference? Physical properties can be observed (changing the size, color, shape of a substance) You can’t always easily see chemical properties (you can’t know if something is flammable until you try to set it on fire)

Characteristic Properties Properties that always stay the same, no matter what the size the sample of the material is –Can be either physical, like density, or chemical, like flammability

Chemical changes Happen when one or more substances are changed into new substances that have new and different properties Signs of chemical changes: change in color or odor, production of heat, bubbling, sound or light being given off Once a chemical change has occurred, you can rarely get back the original substances –Chemical changes change the composition (type) of the matter involved

Which one is it? Are the following physical or chemical changes? boiling water tearing clothes tarnishing silver lighting a match chewing a food breaking a stick rusting nail burning gas in a stove melting ice cream sawing wood digesting food for energy stretching a rubber band