Unit 1+2 - Introduction to Chemistry

Day 1 - The Scientific Method

The scientific method - An organized approach to solve problems

Steps in the Scientific Method:

1. Observe

   • Use your five senses

   • Define the problem

2. Hypothesis

   • “educated guess”

   • Reasonable explanations for what was observed

3. Experiments

   • Tests each hypothesis to prove/disprove them

4. Analysis

   • Compares the results from the experiment to the original hypothesis

5. Conclusion (theory)

   • A hypothesis supported by experimental evidence

Law - Used to describe a natural phenomenon which has been tested over a long time under different conditions

Day 2 - Classification of Matter

Chemistry - The study of matter and the changes it undergoes

Matter - Anything that has mass and volume (everything)

Mass - The amount of matter in an object (how much “stuff”)

Energy - Anything that can do work or produce heat

Weight - The force of gravity acting on an object’s mass

Matters are classified into pure substances and mixtures.

Pure substances - Have uniform and definite composition

• Elements - Found on the periodic table (approx. 118)

  • Described by symbols: H, He, etc.

• Compounds - Formed when elements chemically combine: H20, CO2, NO2

Mixtures - Two or more pore substances physically mixed together.

• In compounds, elements are bonded to each other

• In mixtures, the substances are blended

• No definite composition - cannot assign a fixed ratio (ex: H2O)

Two types of mixtures:

Heterogeneous mixtures - Does not have a uniform composition

• Parts of the mixtures can be physically seen and “picked out” of the mixtures

  • Ex. Cereal, pizza, salad

Homogeneous mixtures - Has a uniform composition

• Parts of the mixture cannot be “picked out”

  • Ex. Sugar, water, milk

Day 3 - Chemical/Physical Changes and Properties

Pure substances have a unique set of chemical and physical properties

Physical properties - Properties that can be measured/observed w/o changing the identity/composition of a substance

• The chemical make-up does not change when these properties are observed

  • Ex. color, odor, texture, taste, freezing point, melting point, density, mass, hardness

Chemical properties - Properties that indicate how a substance reacts with other substances

• These properties are only observed when the substance undergoes a chemical change

  • Ex. Flammable, combustible, burnable, “reacts with…”

Physical Changes - Changes in appearance without changing the composition (Ex. cutting, breaking)

• Changes in state such as: melting, freezing, boiling, subliming (going from a solid to gas)

Chemical Changes (Reactions) - One or more substances react to form new substances with different chemical and physical properties

• The beginning substance is different than the ending substance

  • Ex. Rusting, burning, corrosion, digestion, respiration, decaying

• All chemical reactions can be described by a chemical equations

Law of Conservation of Mass - In any chemical or physical change, matter cannot be created/destroyed

Day 4 - Types of Measurements and Observations

Measurement - A type of observation

• Qualitative measurements - Descriptive

  • Ex. hot, cold, heavy, light, big, blue

• Quantitative measurement - Observations with measuring instruments and includes a number and a unit

  • Ex. ruler, balance, thermometer, 13.5 c, 25 KG

Accuracy - How close a measurement is to the true/accepted value

• Ex. Weighting 50g mass

  • 50.00g - accurate

  • 32.18g - not accurate

  • 49.99g - accurate

Precision - How close multiple measurements are to each other

• Ex. weighting a 50g mass

  • Accurate, precise: Not Accurate, precise:

    50.00g 32.18g

    50.00g 32.18g

    50.00g 32.18g

ACurate = Correct

PRecision = Reproducibility

Day 5 - Introduction to Dimensional Analysis

https://docs.google.com/presentation/d/1AgDm3T_yVV4a9ckTmKlRJEClY50nsCO2h9Nv-FJDN8c/edit#slide=id.p1

Day 6 - Dimensional Analysis Calculations with more that 2 steps

https://docs.google.com/presentation/d/1qLW9ihonLWArZ1UIAjkvCnaUmW0fCvO8a6r1tymVjuU/edit#slide=id.p1