Measuring in Metrics

• Length

  • Distance between 2 points

  • Base Unit

    • Meter

• Volume

  • Amount of space an object takes up

  • Base Unit

    • Liter

• Mass

  • Amount of matter in an object

    • Base Unit

      • Gram

• Temperature

  • Measures the degree of heat in an object

  • Base Unit

    • Celcius

    • Freezing

      • 0

    • Boiling

      • 100

    • KELVIN

      • At 0K all particle motion stops

      • +273 degrees

• Accuracy vs Precision

  • Accuracy

    • How close the measured value is to the true value

  • Precision

    • How close measured values are to each other

• Degree of Uncertainty

  • Depends on the instrument measuring

  • One place beyond measuring device

• Sig Figs

  • Meaningful digits in measurement

  • What was actually measured vs placeholder

Significant Figures Rules

1. Non-zero digits are always significant.

2. Leading zeros (zeros before the first non-zero digit) are not significant.

3. Captive zeros (zeros between non-zero digits) are significant.

4. Trailing zeros in a decimal number are significant.

5. Trailing zeros in a whole number without a decimal point are not significant unless specified by a decimal point.

6. Rounding

   1. If the preceding digit is even round to that even digit

   2. If the preceding digit is off round to the next even digit

Classifying Matter

• States of Matter

  • Solids

    • Fixed shape and volume

  • Liquids

    • Fixed Volume

    • Not rigid in shape

  • Gas

    • Neither fixed volume nor rigid shape

    • Takes on the volume and shape of the container

• Matter can be a pure substance or a mixture

• Atom

  • The smallest part of an element that has properties of elements

• Molecule

  • 2 or more atoms bonded together covalently

• Chemical formula

  • Used to make it easier to describe elements and molecules

• Separation Techniques

  • Filtration

    • Separates compounds, mixture through barriers with fine pores

  • Distillation

    • Separates homogenous solid-liquid mixture, liquid vaporizes leaves solid, recondensed into liquid

  • Chromatography

    • Differences in solubility to separate mixtures

  • Electrolysis

    • Electricity to separate, obtain pure elements

Properties of Substances

• Density

  • Intensive

  • Amount of mass per volume

• Percentage Error

  • |Experimental-Theoretical|/Theoretical

Chemical vs. Physical Changes

Definitions

• Physical Change: A change that affects one or more physical properties of a substance without altering its chemical composition.

• Chemical Change: A change that results in the formation of new chemical substances.

Distinguishing Properties

• Physical Change:

  • Reversible (e.g., melting ice).

  • No new substances formed.

  • Signs

    • Melting

    • Boiling

    • Solubility

    • Vapor Pressure

    • Malleability

    • Ductility

    • Specific Heat

    • Heat of Fuisoom

    • Heat of Vaporization

    • Density

    • Electrical and Heat conductivity

• Chemical Change:

  • Often irreversible (e.g., rusting iron).

  • New substances formed with different properties.

  • Signs

    • Reactivity

    • Stability

    • Heat of reaction

Definitions

• Substance: Homogoenous, elements, and compounds

• Element: A pure substance that cannot be broken down into simpler substances by chemical means; consists of one type of atom.

  • One letter

  • Two letters

    • First uppercase, second lowercase

• Compound: A substance formed when two or more elements chemically bond together in fixed proportions, can be decomposed by chemical changes back into separate elements. FIXED composition, pure substances

• Mixture: A combination of two or more substances that retain their individual properties and can be separated by physical means. NOT chemically bonded.

• Homogeneous Mixture: A mixture that has a uniform composition throughout; components are evenly distributed.

  • Aqueous Solutions

    • Solute dissolved into water

    • Not separated by filtering

    • MUST evaporate

    • TRANSPARENT

    • Example

      • Slat in water

  • Tinctures

    • Solution dissolved in alcohol (ethanol)

    • Some things that can’t dissolve in water dissolve in alcohol

    • Example

      • Tincture of Iodine

  • Amalgam

    • Solid solution, metal dissolved into mercury

    • Examples

      • Silver and gold for dental filling until porcelain

  • Alloys

    • Metals CANNOT chemically bond

    • Mixed to be stronger

    • Examples

      • Iron, rust and soft but mixed with carbon makes steel

• Heterogeneous Mixture: A mixture that consists of visibly different substances or phases; components are not uniformly distributed.

Heterogeneous Mixtures

• Characteristics

  • Not uniform in composition

  • Components can often be separated by physical means

  • Can have different properties in different areas

• Examples

  • Salad: Different vegetables and toppings are distinguishable

  • Sand and salt: Two distinct components that can be separated by dissolving the salt in water and filtering out the sand

Diamotic Molecules

• Certain elements are so reactive they are more stable as pairs

• Two atom molecules

• Examples

  • Oxygen

  • Bromine

Colloids

• Heterogenous Mixtures where tiny particles are dispersed throughout a medium

• Types of Colloids: Include aerosols, foams, emulsions, and sols.

• Tyndall Effect: The scattering of light by colloidal particles, makes the path of the light beam visible.

• Applications: Used in various fields, including medicine (e.g., drug delivery) and food science (e.g., emulsions in dressings).

• Stability: Colloids can be stabilized by surfactants or by controlling particle size and charge.