Chapters 1 & 3 Matter and Energy
I Chemistry
A. Definition
- The study of the structure, properties and reactions of matter.
B. Scientific Method
- a set of general principles used by scientists to study the world
1. Observation
- observations based on measurements are called data
2. Hypothesis
- a testable interpretation of the observations
3. Experiments
- tests that help determine the validity of a hypothesis
- results of experiments can support or falsify a
hypothesis but they cannot prove it to be true
4. Theory
- a hypothesis that has been supported by many experiments
- a theory continues to be tested with new experiments
and may be modified or even replaced
II Law of Conservation of Matter and Energy
- Matter and Energy can’t be created or destroyed, it just changes form
- (E=mc2)
- Einstein
III Energy
- the ability to do work or transfer heat.
A. Potential Energy (stored energy)
-the energy a body possesses by virtue of its position
or composition
B. Kinetic Energy ( energy of motion)
- the energy a body possesses while in motion or
transferring heat.
IV Properties of Matter
A. Physical
-Can be observed without changing the identity of the substance
-ex. Mass, Volume, texture, temperature, density, color
B. Chemical
- Depends on how a substance reacts with other substances
- Changes the identity of the substance
- ex. Flammability, acidity, reactivity
V Changes
A. Physical
- No new substance is formed
- Reversal of the process results in the original substance
- ex. dissolving, phase changes, conductivity, magnetism
B. Chemical Change (reaction)
- A new substance is formed
- involves a new arrangement of atoms, no new atoms are formed
- all biological functions are chemical changes
1. Evidence of a chemical change
A. Release of a gas (fizzing)
B. Color change
C. Precipitate
- an insoluble solid formed from two solutions
D. Energy released or absorbed
2. Two Types of Chemical Reactions
A. Endothermic
- Absorbs energy
- Usually feels cold
Time
- Products contain more energy than reactants
- Usually not spontaneous
- More energy is required to break the bonds of the
reactants than is released when product is formed
B. Exothermic
- Releases energy
- Usually feels hot
Time
- Reactants contain more energy than products
- Usually spontaneous
- Less energy is required to break bonds of reactants than is
released when product is formed
Activation Energy (Ae)
- the energy required to break the bonds that initiates the reaction
3. Reaction Tendencies
- 2 forces in nature
A. All matter seeks its lowest energy state
B. All matter seeks its highest entropy (disorder)
4. Ways to increase the Rate of Reaction
1. Add energy (heat, light, electricity, stir)
2. Increase Surface Area
3. Dissolve in water
4. Catalyst – speeds up reaction rate without being used up
- lowers the activation energy
- enzymes – biological catalysts
VII Classification of Matter
Matter – anything that has mass and takes up space
A. Element
-smallest unit of a substance that maintains its own unique
properties
-examples: periodic table
B. Compound
-Chemical combination of two or more elements
-ex. Water (H20), CO2, salt (NaCl), sugar (C6H12O6)
C. Mixture
-Physical combination of two or more substances each of
which maintains its own unique properties and can be
separated by physical means
1. Homogeneous – composition is the same throughout
2. Heterogeneous – composition is not uniform
Classify the following as A) physical or B) chemical changes.
1___ melting ice
2___ chopping wood
3___ burning paper
4___ dissolving salt in water
5___ digesting food
6___ boiling water
7___ forming clouds
8___ healing a wound
Classify the following as A) Observation B) Hypothesis C) Experiment D) Theory
9___ The sun is bright
10___ Dropping two objects from the same height to see if they fall at the same speed.
11___ An unknown substance is shiny so we believe it will conduct an electric current.
12___ An unknown substance is flammable
13___ Based on numerous experiments we believe that all matter is made up of atoms
Classify the following as A) endothermic or B) exothermic changes.
14___ burning charcoal
15___ melting ice
16___ exploding a firecracker
17___ using a chemical ice pack
18___ boiling water
Classify the following as A) Potential, or B) Kinetic Energy
19___ Energy stored in the sugar molecule
20___ A mill wheel being turned by a running stream
21___ An exploding firecracker
22___ A ball at the top of a hill
Classify the following as A) element, B) compound or C) mixture
23___ copper
24___ chocolate chip cookie
25___ water
26___ sugar
Classify the following as A) heterogeneous or B) homogenous mixtures
27___ salt water
28___ people
29___ rock