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Objectives

• Distinguish between hypothesis, theory, and law as scientific terms

• Describe the science of chemistry

• Differentiate elements, compounds, and mixtures

• Explain the difference between chemical & physical properties & changes

• Identify the signs of a chemical reaction

Identify each of the following as a Physical or Chemical Change. Put a P next to Physical Changes Put a C next to Chemical Changes

| |A piece of wood burns to form ash. |

| |Baking soda mixed with vinegar forms bubbles |

| |You cut your hair |

| |Copper turns green when exposed to the environment |

| |A piece of metal is bent in half |

| |An aspirin is crushed into a fine powder |

| |Water evaporates into steam. |

| |A piece of cork is cut in half. |

| |Diamonds are used to scratch glass |

| |You cook a hotdog |

| |Two clear liquids are mixed and a red color forms |

| |A bicycle chain rusts. |

| |Food is digested in the stomach. |

| |Water is absorbed by a paper towel. |

| |Old ham goes bad in the refrigerator |

| |Hydrochloric acid reacts with zinc and bubbles. |

| |A piece of an apple rots on the ground. |

| |A tire is inflated with air. |

| |A plant turns sunlight, CO2, and water into sugar and oxygen. |

| |Water freezes to form ice |

| |Sugar dissolves in water. |

| |Eggs turn into an omelet. |

| |A popsicle melts. |

| |A piece of paper is crumpled up |

| |Turning brownie mix into brownies. |

| |Thousand Island dressing and mayonnaise are mixed to make “secret sauce” for hamburgers |

| |Hair curls when the humidity increases |

| |Meat blackens when cooked too long on a barbecue |

| |Milk curdles if a few drops of vinegar are added |

| |Dry ice gradually sublimes |

| |Salad dressing separates into layers after standing |

| |Spilling acid on cotton jeans creates a hole in them |

| |Alka Seltzer neutralizes stomach acid |

Fill in the Blanks

The scientific ______________ provides a logical approach to the solution of scientific problems. The steps of the scientific method include observations, ______________, ______________, theories and ______________ laws. An ______________ is information gathered from the senses. A hypothesis is a proposed explanation or reason for what is observed. A scientific experiment must be ______________ for it to be valid. A theory is a broad and extensively tested ______________ of why experiments give certain results. A scientific ______________ describes a natural phenomenon but does not explain it.

Question

You have a sore throat, so you go to the doctor. The doctor examines your throat and says she thinks you have strep throat. She takes a sample to test for strep bacteria. What parts of the scientific method are you and the doctor applying? Name them all and which part of the scenario they apply to.

What are the five signs of a chemical reaction?

1. ____________________________________

2. ____________________________________

3. ____________________________________

4. ____________________________________

5. ____________________________________

Label each model as a compound, element, or mixture.

[pic]

_______________ ______________ ______________ _______________

Identify as either elements, compounds, homogeneous mixtures (solutions) or heterogeneous mixtures:

| |copper (II) sulfate |

| |Kool Aid |

| |wood |

| |gold |

| |pure water |

| |sand |

| |carbon dioxide |

| |plastic |

| |air |

| |manganese |

| |apple pie |

| |milk |

| |a teaspoon of sugar |

| |cement |

| |aluminum foil |

| |salad dressing |

| |muddy water |

| |a bag of various colored marbles |

| |sugar dissolved in water |

| |pond water |

| |zinc chloride |

| |salt water |

| |gravel |

| |blood |

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