Tell how compounds can be separated into their individual elements. The opposite of a mixture is a pure substance. Using this information, write what you think is the definition of a pure substance.

A Pure Substance is made of only one kind of molecule, has definite properties, and every sample is the same. Pure substances are put into two categories: elements or compounds. EXAMPLES: Sugar, water, hydrogen, oxygen HOO

Take the pure substance sugar… Sugar is a compound made of the elements carbon, hydrogen, and oxygen. Think about the white crystals in this bowl. Do they seem like the black carbon of pencil lead and the colorless hydrogen and oxygen gases? When atoms/elements combine into compounds, the new substance has properties that are different from the elements.

LAB: Separating a Pure Substance Key Points to Remember: Sugar is a compound and water is a compound, both pure substances! Compounds are made of elements! Compounds can be separated, but chemically, because the parts that make them up are chemically combined and we have to break those bonds! So, how can we separate the compound sugar into the elements that make it up? (Hint: think of a chemical property of sugar!)

Separation of a compound---sugar! Sugar has a good chemical property that allows us to separate it---it’s flammable! We can burn it! By burning it, we are performing a chemical change that will make new substances ----the substances/elements that make up sugar! 1.Make a hypothesis on your worksheet. 2.Follow the procedure on your “Burning Sugar” Lab. 3.Clean up ! 4.Complete the observations & conclusions on the lab sheet.

Name: _______________ Class: _______________ Hypothesis: I think… ____________________________________________________ Because… _____________________________________________________________ Observations: What did you observe during the experiment? ____________________ ______________________________________________________________________ Data/Results: Burning sugar is a _______________ reaction because _____________ ______________________________________________________________________

7 EXPLANATION: As sugar is heated the carbon and hydrogen and oxygen atoms unhook and recombine to make carbon and water.

Sugar Molecule Model (Compound) Water molecules Carbon molecules How could we now separate the pure substance water into its individual elements?

Compound Sugar One molecule of sugar is actually made of 12 Carbon atoms, 22 Hydrogen atoms, and 11 oxygen atoms. That’s a big molecule! Some chemical bonds are strong and hard to change. Others break apart easily. Think of window glass. Do you think its chemical bonds break easily? You guessed right if you said “NO”. Its chemical bonds are held together very strongly. Whereas, sugar is a compound that has weaker chemical bonds and can be more easily broken. Was sugar easy to separate into the atoms/elements that make it up?

Conclusion Complete the chart telling whether each substance is a pure substance or a mixture. (Hint: Can it be physically separated or is there a chemical bond?) SUBSTANCE Pure mixture Substance Sugar Trail mix M & M colors Salt Sand at the Beach

Extension Activity Balancing equations battleships