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