Honors Chem Unit 4 Review

Gas

Particles are independent, widely separated, with no attractive forces between them. They fill the volume of the container

Liquid

Particles constantly make and break temporary attractions between each other. Particles can slop past one another easily. They take the shape of the container

Solid

Strong attraction between particles lock them into a fixed arrangement

Pure Substance

These have fixed compositions, one set of intrinsic physical properties (density, mp,bp). and can be separated only be chemical means

Mixture

These have variable composition. Their physical properties vary depending on the composition. They can be separated by physical means.

Elements

These cannot be broken down into simpler substance by physical or chemical means. The smallest particle of this is called an atom.

• All elements are Pure Substances

Compound

These are made of elements in fixed mass ratios. They can be broken down into simpler substances by chemical means.

• All compounds are Pure Substance

Molecule

Any 2 or more atoms bonded together

Homogeneous

Exists in one phase only and has uniform properties throughout the sample

• Appears uniform(same) throughout; Components are evenly distributed

Heterogeneous

May exists in more then one phase and have variable properties in different parts of the sample

• Componenets are not evenly distributed;can see seperate components

Dissolve: Water has a much lower boiling point than salt

Filter: After dissolving the salt, the salt water will pass through the filter but the sand particles are too large so they won’t pass through

Which technique would be useful to separate a mixture of sand and salt? Of salt and water? Why?

Dalton

Diagram: Billiard Ball Model, Solid, Individual spheres that can bond

Evidence: Priestley Lavoisier + Diamond experiments

Justification: Compounds can be broken apart into simpler substances. Simpler Substances can combine in fixed ratios. In both cases, new properties emerge

Thomson

Diagram: Chocolate Chip Cookie Model, small negatively charged electrons and positive charged spread spread throughout

Evidence: Cathode Ray Experiments

Justification: The Cathode Ray itself is a beam of electrons. It moves away from the negative end of the magnet. Light dosen’t do that, Matter does.

Rutherford

Diagram: Most of the atom is empty space, Positive charge is condensed in the nucleus

Evidence: Gold Foil Experiment

Justification: Most positively charged alpha particles passed right through the gold. The small % that were deflected off that straight path did so because they approached the dense positive nucleus.

Bohr

Diagram: Electrons orbit the nucleus at specific distances (energy levels)

Evidence: Line Emission Spectra

Justification: Electrons jump up to higher energy levels when they absorb energy. When they fall back down, they release energy we can see as light. Each line on the spectrum is a specific fall an electron made. They only have specific colors (not all wave-lengths)