Unit 3: Chemical Composition

Yes

Yes

Yes An element is a substance which cannot be split further into simpler substances by any chemical means. An element is a pure substance which cannot be broken down into two or more simpler substances by chemical reactions.

Yes

Yes Elements can exist as a single atom or molecule.

Yes An element is made up of only one type of atoms. Atoms of each element are different from atoms of any other element.

Atoms are the smallest particles of an element that have the chemical properties of that element.

There are about 118 elements.

98 elements are found naturally on Earth. The rest are made artificially in the laboratories!

Metalloids are elements that show some properties of both metals and non-metals. Metalloids share properties of both metals and non- metals. Elements that are metalloids are B, Si, Ge, As, Sb, Te, Po

Shiny solids, except mercury - a liquid at room temperature Have high melting points and boiling points. High density Malleable ((of a metal or other material) able to be hammered or pressed into shape without breaking or cracking.) Ductile ((of a metal) able to be drawn out into a thin wire.) Good thermal conductivity and electrical conductivity Sonorous (capable of producing produce a ringing sound when hit.)

Dull solids, liquids or gases Have low melting points and boiling points Low density Brittle (Break easily into pieces) Poor thermal conductivity and electrical conductivity Non-sonorous (not capable of producing a ringing sound when hit.)

(of a metal or other material) able to be hammered or pressed into shape without breaking or cracking.

(of a metal) able to be drawn out into a thin wire.

produce a ringing sound when hit.

Break easily into pieces

1st letter is always capitalized any other letter that follows the 1st letter is in lower case

A compound is a substance which consists of two or more elements chemically combined together in a fixed composition. Can be broken down into two or more simpler substances by chemical methods Has different properties from its constituent elements Elements in a compound are present in fixed proportion Has a fixed melting and boiling point. E.g. water (hydrogen & oxygen) sodium chloride (sodium & chlorine) sugar (carbon, hydrogen & oxygen)

Yes Compounds are formed by chemical reactions Many elements combined directly to form compounds Example: Burning of magnesium in oxygen to form magnesium oxide (magnesium + oxygen)

Yes The properties of compounds are different from the properties of its constituent elements.

Yes Compounds have fixed compositions. E.g. Water always contains 11% hydrogen & 89% oxygen by mass.

Compounds can only be broken down into simpler substances by chemical methods, such as decomposition. Decomposition is usually carried out using heat, electricity or even bacteria.

Compounds: Made up of two or more types of atoms Can be broken down into two or more simpler substances by chemical methods Elements: Made up of one type of atoms only Cannot be broken down into any simpler substances

Compounds: Made up of two or more types of atoms Can be broken down into two or more simpler substances by chemical methods Has different properties from its constituent elements Elements in a compound are present in fixed proportion Has a fixed melting and boiling point. Mixture: Made up of two or more substances not chemically combined together. Can be separated into pure substances by physical method Has similar properties as its constituent components Components in a mixture are not present in fixed proportion It melts/boils over a range of temperature.