Properties of Matter

• Matter - anything that has mass and takes up space

• Chemistry - the study of the properties of matter and how matter changes

• Pure substance - a single kind of matter that has a specific makeup and a specific set of properties

• examples: elements, table salt, water, baking soda

• Element - a pure substance which cannot be broken down into any other substances by chemical or physical means

• Physical Property - a characteristic of a pure substance which can be observed without changing it into another substance

• examples: hardness, texture, color, boiling point, melting point, freezing point, etc.

• Chemical Property - a characteristic of a pure substance that describes its ability to change into different substances

• examples: flammability, ability to rust/tarnish, ability to react with acids, etc.

• Molecule - two or more atoms chemically bonded together

• water, carbon dioxide, methane, etc

• Compound - a pure substance made of two or more different elements chemically combined in a set ratio

• All compounds are molecules but not all molecules are compounds.

• Compounds have properties that are different from those of the uncombined elements.

• Mixture - two or more substances that are mixed together, but are not chemically combined

• the substances can often be separated from each other by physical means such as filtering, using magnets, boiling, etc.

• each substance keeps its individual properties and the substances are not combined in a set ratio (ex: soil, salt water)

• Heterogeneous Mixtures - the different substances found in the mixture can easily be seen

• examples: soil, a salad, a chocolate chip cookie, etc.

• Homogeneous Mixtures - the different substances found in the mixture cannot be seen

• examples: sugar cookies, kool-aid, etc

• solution - a homogeneous mixture in which one substance is dissolved into another substance

• examples: Kool Aid, brass (a solid solution of copper and zinc), air (N2 and O2 with other gases)

• Walking Through Paper

• Ivory Soap

• “The Soap That Floats”

• Bromothymol Blue

• pH indicator

• CO2 + H2O make carbonic acid

• Carbon Snake

• exothermic reaction

• Physical Change - a change in a substance that does not change its identity

• change in size, shape, or phase (solid, liquid, gas)

• does not change what the substance is

• is often reversible

• examples: dissolving, crushing, cutting, melting, freezing, evaporating

• Chemical Change - a change in which one or more substances combine or break apart to form new substances

• changes the chemical makeup of the substance

• often accompanied by release of a gas, color change, odor, release of heat

• usually not reversible

• examples: burning, rusting, baking, digestion, photosynthesis

Demo Flashback: Physical or Chemical Change?

• Walking through paper

• Ivory Soap

• Bromothymol Blue

• Carbon Snake

• Conservation of Mass - matter cannot be created or destroyed through chemical or physical changes

• In a chemical reaction, all atoms present at the start of a reaction are present at the end

• ex. Photosynthesis: 6CO2 + 6H2O → C6H12O6 + 6O2

• Solid

• has a definite shape and a definite volume

• particles are packed tightly together in a fixed position; can vibrate slightly

• crystalline solids have particles arranged in a regular, repeating pattern

• melt at a specific temperature

• examples: sugar, salt, snow, quartz

• amorphous solids have particles which are not arranged in a regular pattern

• when heated, become softer and softer

• examples: wax, rubber, glass, plastic, butter

• Liquid

• has a definite volume, but does not have a definite shape

• particles are packed tightly together, but are free to move around each other (fluid)

• surface tension forms within liquids as the molecules of the liquid are attracted to each other

• surface acts like it has a thin skin

• viscosity - a liquid’s resistance to flowing

• honey has a higher viscosity than water

• Gas

• does not have a definite shape or a definite volume; expands to fill its container

• fluid

• compressed = higher pressure

• adding energy will cause a gas to expand

• taking energy away will cause it to contract

• Phase Changes/Changes of State

• Melting - changing from a solid to a liquid

• thermal energy increases; particles break free from their fixed positions

• melting point is the same temperature as freezing point (water = 0°C or 32°F)

• Freezing - changing from a liquid to a solid

• thermal energy decreases; particles slow down and begin to form the regular patterns of a solid

• Sublimation - changing from a solid to a gas

• bypass the liquid stage

• examples: snow disappearing, dry ice

• Vaporization - changing from a liquid to a gas

• on the surface = evaporation

• within a liquid = boiling

• the lower the atmospheric pressure is, the lower the boiling point will be

• Water boils at 100°C in San Diego (sea level), but at 95°C in Denver (1,600 m elevation)

• Condensation - changing from a gas to a liquid

• Particles lose energy, slow down, and condense into a liquid

• examples: cold drink on hot day, mirror after shower, dew on leaves

• Thermal expansion - the tendency of matter to change in volume in response to a change in temperature

• Water contracts as it is cooled until it reaches 4°C, then expands while it freezes (4°C - 0°C).