chemistry unit2 part3 - elements compounds and mixtures
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Matter and changeUnit 2 Part 3 – Elements, Compounds, and Mixtures
TAKS Student Expectation• Integrated Physics and Chemistry
(7) Science Concepts. The Student knows the relationship between properties and its components. The Student is expected to:– (E) Classify samples of matter from
everyday life as begin element, compounds, or mixtures.
Mixtures• Mixture – two or more substance
that can be separated by physical means
• Physical types of separation– Filtration to separate a solid from a
liquid.
– Distillation to separate a pure liquid from dissolved solid impurities which have a very high boiling point.
– Fractional distillation to separate liquids with a range of different boiling points, especially if relatively close together.
– Evaporation to remove a solvent to leave a solid behind.
– Crystallization to get a pure solid out of a solvent solution of it.
– Chromatography – separate mixtures based on the different masses of substances.
• Types of mixtures– Heterogeneous – suspensions, colloids– Homogeneous – solutions
Pure Substances• Pure - only one substance is present
in the material.• Has a constant (fixed) melting and
boiling point.
Compounds• Compound – a pure substance that
cannot be broken down by physical change, but can be broken down by chemical change.
• 2 Types– Molecules – atoms of the compounds share electrons.
– Formulas – atoms in the compound exchange electrons.
• Compounds obey the Law of Definite Proportion – 1794 - John Louis Proust
(France) publishes work. Accepted by scientific community in 1811.
– Law states in a pure compound, the elements combine in definite proportions to each other by mass
• Ex: water is always 88.81% Oxygen to 11.19% Hydrogen
Elements• element – a substance that cannot be
broken down into other substances by chemical change or a physical change.
• Elements typically contains only one kind of an atom. (although certain compounds, like oxygen, can be a compound of itself)
• All known elements are listed on the Periodic Table.
Putting it all together• Draw the following diagram which
ties together mixtures and pure substances