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Unit 1
Matter - anything that has mass and takes up space, exists as either a Solid, Liquid, Gas, has physical and chemical properties. Matter is classified as elements, compounds and mixtures.
- Liquid: not rigid, no fixed shape, fixed volume
- Gas: no rigid, not fixed shape, no fixed volume
- Solid: rigid, fixed shape, fixed volume
Atoms - building blocks of all matter. There are approximately 100
Parts of an Atom
- Protons- positive charge (+) found in the nucleus
- Neutrons- no charge makes up most of the mass of an atom.
- Electons – negative charge(-), moves around the nucleus in the
electron cloud.
Element - made up of one type of atom
Elements are identified by their atomic number and chemical symbol.
Chemical Symbol: abbreviation of the name.
Periodic table (PT): elements are arranged in PT by atomic numbers
To Find the number of:
- Neutrons - subtract the # of protons from the atomic weight (mass)
- Protons - Atomic Number
- Electrons – equals number of protons
How to count the number of atoms in a compound or molecule:
Most abundant elements on Earth are:
Oxygen Carbon Hydrogen Nitrogen
Molecules, Compounds, Mixtures & Elements
Molecules: made of 2 or more atoms that are bonded together chemically.
Compound is a molecule that contains at least 2 different elements. All compounds are molecules but not all molecules are compounds.
Chemical Formula - shows how many of each kind of atom are resented in a molecule or the compound. Examples: Molecules: H2, N2 Compound: H2O CO2 Example: water has 2 hydrogen atoms and 1 oxygen atom
Mixtures:
- Two or more substances held together by physical forces
- No chemical change takes place
- Each item retains its properties in the mixture
- They can be separated physically
Chemical and physical changes both involve a change in energy.
Chemical Change -change in matter that produces a new substance, can not be separated physicallyExamples: Flammability of substance, gives of heat or is cold, color change
Physical Change – no new substance is formed, separates easily by physical means Examples: texture, boiling point, color