• Atoms are the smallest unit of an element that maintains the properties of that element.
• The most basic ingredients to all matter
• Atoms can be combined in three majors ways:
– To make elements
– To make compounds
– To make mixtures

• We can use legos to help us figure out the differences between atoms, elements, compounds, and mixtures
• Elements are made up of one or more of the same kind of atom chemically combined
• Compounds are made up of different kinds of atoms chemically combined. They have different properties than the atoms that make them up
• A mixture contains a variety of elements and compounds that are physically combined.

• Elements and compounds make up pure substances
• A pure substance has definite physical and chemical properties
• No matter how much of a pure substance you have, it will always have the same properties

• Pure substances are made up of one type of particle
– One type of element or one type of compound
– Each compound is a chemically combined particle or molecule
– Ex. Every water molecule is exactly the same

• Pure substances cannot be formed or broken down by physical change
– Chemical bonds that are holding the atoms together require a lot of energy to break. In order to do this we need a chemical change.
– If we were to break apart water we would end up with 2 hydrogen atoms and an oxygen atom

• Based on their chemical and physical properties we can categorize elements
• Some of these categories include metals, nonmetals, or metalloids
• Over 100 elements are known to exist
– They are found on the periodic table
– The periodic table separates the metals, nonmetals, and metalloids by the staircase

• By pH
– Acidic if pH is lower than 7 (sharp sour taste)
– Basic if pH is higher than 7 (slippery feel, bitter)
– Neutral if pH is 7 (form when acids and bases react) examples pure water and salt
– We test pH using litmus paper that changes color depending on the pH
– DO NOT TASTE OR TOUCH IN LAB

• As Organic or Inorganic
– Organic has carbon and hydrogen atoms
– Organic would be in foods and other types of living things
• By their role in the body
– Biochemicals
• Carbohydrates
• Lipids
• Proteins
• Nucleic acids

• A mixture is a combination of two or more substances combined physically
• Mixtures are made up of more than one type of particle
– The properties of these particles remain unchanged
– Mixtures do not have their own defined properties
• Mixtures can be separated by physical changes

• By hand
• Centrifuge (density)
• Magnets
• Boiling off solutions

• A heterogeneous mixture is one that does not have inform composition
• A homogeneous mixture is one that is evenly spread throughout
– When something totally dissolves it forms a homogeneous mixture

• Suspension- mixtures in which the particles of a material are spread throughout a liquid or gas but are too large to stay mixed without being shaken or stirred
– Heterogeneous

• Solutions- one substance is dissolved in another substance
– Homogeneous

• Colloids- between a suspension and solution
– Particles are spread throughout but do not settle quickly
– Milk and gelatin are good examples
– Heterogeneous despite looking homogeneous