Matter
Atom - the smallest unit of an element that has the properties of that element From the Greek word for indivisible
3 subatomic particles Proton - positively charged particle in the nucleus of an atom Neutron - neutral (un-charged) particle in the nucleus of an atom Electron - negatively charged particle that orbits the nucleus of an atom
The number of protons determines what element the atom is Atoms are electrically neutral (have the same number of protons and electrons)
Atoms of the same element can have different numbers of neutrons; these atoms are called isotopes
Periodic Table - a chart of the elements showing the repeating pattern of their properties
Using the periodic table: Atomic Number (number of protons) Symbol Name Atomic Mass (average mass of isotopes)
Fill in the blanks.
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 (N 2 and O 2 with other gases)
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
Walking Through Paper
Bromothymol Blue ph indicator CO 2 + H 2 O make carbonic acid
Ivory Soap The Soap That Floats
Carbon Snake exothermic reaction
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: 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2
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).