Matter and Energy Flashcards
Matter
Anything that takes up space of volume and has mass
Pure substances
Elements and compounds
Elements
Substances that cannot be broken down or decomposed into simpler substances by chemical means
Ex: H2(g), Ne(g)
Compounds
2 or more different elements chemically bonded together
LiH(s), NaCO3(s)
Binary compound
Contains 2 different elements
Ternary compound
Contains 3 different elements
Mixtures
Homogenous and heterogeneous
Homogenous mixture (solution)
- Observe 1 distinct phase
- Particles are uniformly dispersed
- Clear, transparent
- Cannot be filtered
Ex: NaCl(aq), CuSO4(aq)
Heterogenous mixture
- Observe 2 or more distinct phases
- Particles are unevenly dispersed
- Not clear and not transparent
- Can be filtered
Ex: Greek salad, oil and water, soil
How do you remove salt from water?
Heat the solution in order to evaporate out the water and be left with salt
Physical properties
Observed using 5 senses
Examples of physical properties
Texture, taste, shape, color, smell, phase of matter, density, solubility
Physical properties of metals
Luster, conductivity, malleability, ductility, tenacity
Why do metals conduct electricity?
Due to a sea of mobile electrons
Malleability
Can be hammered into sheets
Ductility
Can be drawn into wires
Tenacity
Strength
Physical change
A change that does not alter the chemical properties of the substance
Phase changes
A type of physical change
Melting
Solid to liquid
Evaporation
Liquid to gas
Sublimation
Solid to gas
Freezing/solidification
Liquid to solid
Condensation
Gas to liquid
Deposition
Gas to solid
Chemical properties
Describe how a substance reacts
Examples of chemical properties
Inert (noble gases), radioactivity, acidity, flammability, combustibility, rust, sours, spoils
What substances sublime readily?
Iodine and carbon dioxide (dry ice)
Which substance is flammable?
Hydrogen
Which substance is combustible?
Methane
Which substance supports combustion but is not combustible?
Oxygen
Chemical changes
Production of new substances through a reaction
Potential energy
Stored energy
Kinetic energy
Energy of motion
6 other types of energy
1) Thermal (heat)
2) Solar (sun)
3) Nuclear
4) Mechanical (pulley, lever)
5) Chemical (batteries)
6) Electrical
Law of conservation of energy
Energy cannot be created or destroyed, it can only change its form
Energy units
- calorie/kilocalorie
- joule/kilojoule
1 calorie = 4.18 joule
When bonds are broken,
Energy is absorbed
When bonds are formed,
Energy is released
Where is energy stored?
In bonds between atoms
Endothermic reaction
Heat is absorbed and the walls of the container become cool
Exothermic reaction
Heat is released and the walls of the container become warm
Is a combustion reaction endothermic or exothermic?
Exothermic
Temperature
A measure of a substance’s kinetic energy
Freezing/melting point
0°C and 273K
Boiling/condensation point
100°C and 373K
Absolute zero
All motion stops at 0K
Celsius to kelvin conversion
°C + 273 = K
Kelvin to celsius conversion
K - 273 = °C
Endothermic phase changes
Melting, evaporation. sublimation
Exothermic phase changes
Freezing, condensation, deposition
Direction of heat flow
Heat flows from the hotter object to the colder object
Phase changes take place at…
Constant temperatures
Potential energy increases as…
The distance between particles increases
Reaction coordinate
The path that a reaction takes
Activation energy
Minimum amount of energy that must be added to the reactants to start the reaction
Activated complex
Intermediate stage between reactants and products, transition species
Heat of the reaction, delta H, or enthalpy
Heat of the products - heat of the reactants
If the heat of the reaction is positive, the reaction is…
Endothermic
If the heat of the reaction is negative, the reaction is…
Exothermic
How does a catalyst affect the potential energy diagram?
1) Provides an alternate pathway
2) Decreases the activation energy of the forward and reverse reaction
3) Decreases the energy of the activated complex
*Doesn’t affect enthalpy
Calorimetry
The science of measuring heat lost or gained in a reaction
Calorimeter
Device used to measure energy changes
Specific heat capacity
For every one gram of water, 4.18 J of heat must be added to raise the temperature by 1°C
Why do metals have low specific heats?
They are conductors of heat and electricity
Specific heat capacity formula
q = m C delta T
Why can’t we use the formula q = m C delta T for phase changes?
There is no change in temperature, so delta T = 0°C
Heat of fusion
Melting and freezing
Heat of fusion formula
q = mHf
Heat of vaporization
Boiling and condensation
Heat of vaporization formula
q = mHvap
