Chemical Building Blocks

Chapter 1: Introduction To Matter

Section 1: Describing Matter

Matter

  • anything that has mass or takes up space

3 examples of matter:

Properties of Matter

Chemistry

  • study of properties of matter and how matter changes

Substance

  • pure kind of matter that is made of sets of particles

3 Pure Substances

  1. table salt (NaCl)
  1. table sugar
  1. baking soda

3 mixtures:

  1. milk
  1. eggs
  1. fruit
  1. Physical Properties of Matter
  • Characteristics that can be observed without the substance changing into something else

Examples

  • Freezing point, hardness, texture, color, solid, liquid, gas, dissolves in water, *metals=luster, conduct heat and electricity, magnetism
  1. Chemical Properties of Matter
  • characteristic of a pure substance that describes its ability to change into different substances.

Examples

  • Flammability or heat, ability to react, creation of something new, gas given off

Elements

What is an element?

  • pure substance that cannot be broken down into any other substances by chemical or physical means
  • Simplest substances
  • Each element can be identified by its chemical properties

Ex: Aluminum (Al), Copper (Cu), Carbon (C), Oxygen (O)

Particles of Elements-atoms

Atom

  • basic particle from which all elements are made
  • smallest possible piece of matter
  • give elements their special properties
  • Nucleus-positively charged center in the middle of the atom surrounded by a “cloud” of negative charge

When atoms combine

Chemical Bond

  • force of attraction between 2 atoms

Molecule

  • groups of 2 or more atoms held together by chemical bonds
  • Ex: water (H2O)

Compounds

  • pure substance made of 2 or more elements chemically combined in a set ratio
  • compounds have different properties than uncombined elements
  • Ex: water is a liquid as a compound, but its elements are both gases (Hydrogen and oxygen)
  • Sugar=C12H22O11

Chemical Formula

  • represents a compound, shows the elements in the compound and the ratio of the atoms
  • Ex: CO2 (carbon dioxide)
  • C=1, O=2
  • 1:2 ratio of carbon to oxygen

Mixtures

  • made of 2 or more substances that are together in the same place but not chemically combined
  • each substance in a mixture keeps its individual properties

Heterogeneous Mixture

  • can see the different parts
  • Ex: soil, oil and water, cookie dough

Homogeneous Mixture

  • cannot see the different parts
  • Ex: air, salt water, alloys (brass, bronze)
  • Solution-homogeneous mixture, does not have to be a liquid
  • Ex: air (N2, O2, and other gases), brass

Separating Mixtures

  • Easier to separate a mixture than a compound
  • Fig 10: using a magnet, filtering the mixture, distilling a liquid solution, evaporation

Chapter 1: Introduction to Matter

Section 2: Measuring Matter

Weight and Mass

Weight

  • measured with a scale
  • measure of the force of gravity on you
  • Gravity- force that attracts all the objects toward the center of the planet
  • Changes with locations because different planets have different forces of gravity

Mass

  • measurement of the amount of matter in an object
  • mass does not change with location because the total amount of matter in your body will not change
  • scientists prefer to measure matter with mass, not weight

Units of Mass

  • kilogram (kg), gram (g)

International System of Units (SI)

  • system scientists (and us too!) use to measure matter

Volume

  • amount of space that matter occupies
  • Solids, liquids, and gases have volume

Units of Volume

  • Liter (L), milliliter (mL), cubic centimeter (cm3)

Calculating Volume

  • Solid objects= cm3
  • Rectangular objectsvolume=lengthXwidthX height
  • Shapes other than rectangles use water displacement with a graduated cylinder

Find the volume of this brick.

Length: 12 cm

Width: 8cm

Height: 6cm

Density

  • relates the mass of material in a given volume
  • density of water=1g/cm3

Units

  • grams per cubic centimeter (g/cm3)

Equation

Density=mass/volume

Sample problem

Sinking or Floating?

  • Objects with a density greater than 1g/cm3 will sink
  • Objects with a density less than 1g/cm3 will float

Using Density

  • Physical property
  • Can identify unknown substances

Chemical Building Blocks

Chapter 1: Introduction to Matter

Section 3: Changes in Matter

Physical Change

  • Any change that alters the form or appearance of matter but does not make any substance in the matter into a different substance
  • Substance is still the same substance after physical change

Example:

  • Make a sandcastle out of sand

Changes of State

  • Solid  liquid  gas
  • Ex: puddle of liquid water turning into a gas (evaporation)

Changes in Shape or Form

  • Dissolving-sugar water in a pan will leave a crust of sugar when all the water dissolves
  • Bending, crushing, breaking, chopping, filtration, and distillation

Chemical Change

  • Change that produces 1 or more new substances
  • Aka chemical reaction
  • Produces new substances with different properties from the original substances

Examples of Chemical Change

  • rusting, hydrogen peroxide bubbling on a cut
  • burning of methane on gas stove=combustion
  • electrolysis, oxidation(rusting), and tarnishing

Conservation of Mass

  • Law of Conservation of Mass
  • Matter is not created or destroyed in any chemical or physical change
  • When methane burns, you would find the same amount of carbon dioxide and water in the air that was originally burned

Matter and Thermal Energy

Energy

  • Ability to do work or cause change
  • All physical/chemical changes involve change in energy

Temperature

  • Measure of the average energy of random motion of particles of matter
  • Warm particles have more energy than cold
  • Amount of thermal energy something has

Thermal Energy

  • Total energy of all particles in an object
  • Feeling hot or cold
  • Warm cold objects

Thermal Energy and Changes in Matter

  • Endothermic Change- change in which energy is taken in
  • Thermal energy is absorbed
  • Ex: Ice melting
  • Exothermic change-releases energy
  • Thermal energy given off
  • Ex: Combustion

Chapter 1: Introduction to Matter

Section 4: Energy and Matter

Forms of Energy

Related to changes in matter

May include: kinetic, potential, chemical, electromagnetic, electrical, thermal

Kinetic Energy and Potential Energy

Kinetic Energy-energy of matter in motion

Ex: rolling bowling ball

Potential Energy-energy an object has because of its position

Ex: diver on top of a diving board

Chemical Energy-internal energy stored in the chemical bonds between atoms

  • Form of potential energy

Ex: chemical reaction between magnesium strip and fire

Electromagnetic Energy-a form of energy that travels through space as waves

Ex: visible light, radio waves, infrared rays (heat), microwaves, ultraviolet waves, X-rays

Electrical Energy-energy of electrically charged particles moving from one place to another

Ex: electrolysis (separating hydrogen and oxygen from water)

Electrodes-metal strips placed in a solution connected to wires which use energy to separate substances

Transforming Energy

During chemical changes, energy may be changed to other forms, which can be changed to chemical energy

Ex: photosynthesis-Plants transform electromagnetic energy chemical energy