Properties and Changes of Matter Chapter 20

Properties of Matter

Physical and Chemical Properties Section 1

Physical Properties

Physical Properties Physical properties characteristics you can observe without changing the composition of the substance some are observed using your 5 senses how something looks, smells, sounds or tastes examples – color, odor, shape, texture, state of matter

Physical Properties Size-Dependent Properties property depends on the size of the sample property changes if the sample gets bigger or smaller examples: Volume – amount of space an object occupies; multiple the length X width X height = (cm3) Mass - how much matter an object contains (g) Weight - force of gravity on an object (N)

Physical Properties Size-Independent Properties property does not depend on the size of the sample property does not change if the size of the sample changes examples: density – amount of mass in a given volume D = M ÷ V = (g/cm3)

Physical Properties examples: solubility – number of grams of one substance that will dissolve in 100 g of another substance melting point – temperature when a solid changes into a liquid boiling point – temperature when a liquid turns into a gas magnetism – substance pulls iron towards it

Physical Properties examples: ductility (ductile) – ability to be made into wires, like copper

Physical Properties examples – elasticity – the ability to stretch and not break

Physical Properties examples: malleability – ability to be hammered into sheets (like gold)

Chemical Properties

Chemical Properties chemical properties – characteristic that cannot be observed without altering the substance examples: flammability – ability to burn tendency to rust – oxidize, exposure to oxygen and water reactivity – reacts with other materials to cause a change in substance

Section 1 Review How are your senses important for identifying physical properties of matter? It is through the senses that you gather information about the world around you. For example, you use your senses to detect an object’s shape, color, texture, taste, sound, temperature, smell, weight, state and behavior, as well as to make measurements.

Section 1 Review Describe the physical properties of a baseball. A baseball is a solid, its shape is spherical, its texture is smooth yet bumpy near the stiches, its color is red and white. If I had the right tools, I could measure its mass, volume and density.

Section 1 Review Explain why solubility is a size independent physical property. Solubility is a ratio of two size dependent properties. As one property increases, so does the other one. The ratio does not change.

Section 1 Review How do chemical and physical properties differ? A physical property can be observed without changing the composition of the substance. A chemical property cannot be observed without altering the composition of the sample.

Physical and Chemical Changes Section 2

Physical Changes

Physical Changes form or appearance of matter changes composition does not change still made from the same elements

Physical Changes

Physical Changes Examples Changing shape – only changes the form of matter cut tear bend crumple

Physical Changes

Physical Changes Examples Dissolving– particles spread out in a solution composition stays the same only form changes

Physical Change Examples Changing states vaporization or evaporation – liquid to gas condensation – gas to liquid sublimation – solid to gas deposition – gas to solid

Chemical Changes

Chemical Changes substance is changed into another substance composition changes changed at a molecular level

Chemical Changes

Chemical Changes Signs of a Chemical Change color changes leaves undergo chemical change in fall apple turns brown when exposed air marshmallow or bread turns brown when toasted

Chemical Changes

Chemical Change Signs Exothermic = Release heat. Gets warm. energy either absorbed or released light is given off (flame) temperature changes (heats up or cools down) sound produced (explosion) Exothermic = Release heat. Gets warm. Endothermic = Absorb heat. Gets cold.

Chemical Changes

Chemical Change Signs odor changes new smell is produced the smell of spoiled milk rotting eggs the way the air smells after a thunderstorm

Chemical Changes

Chemical Changes Signs gases or solids (precipitate) are produced bubbles form – gas produced solid forms from liquids, like spoiled milk

Chemical Changes Signs not easily reversed cannot be changed back into its original substance by physical means substance that existed before the chemical change no longer exists

Section 2 Review List five physical changes that you can observe in your home. Physical changes at home could include cutting paper, pouring milk on cereal, mowing the lawn, melting ice. None of these change the composition of the material.

Section 2 Review Determine what kind of change occurs on the surface of bread when it is toasted. The toast is an example of a chemical change. The bread’s color and odor changes and energy.

Section 2 Review How is mass conserved during a chemical change? The particles within matter are rearranged, but the total mass of the matter remains the same.

Section 2 Review A log is reduced to s small pile of ash when it burns. Explain the difference in mass between the log and the ash. The difference in mass is a result of the mass of gas that was formed in the reaction and escaped.