Unit A Energy and Matter in Chemical Change : Section 3.0 Flashcards
What are the elements on the left side of the equation called?
Reactants
What are the elements on the right side of an equation called?
Products
What are indications of chemical reactions?
- Formation of gas
- Formation of solids
- Energy Changes
- Change in odour
What is happening during an explosion? What are the states of matter? How is the volume affected?
A small amount of a solid or liquid converts quickly to a large volume of gas
What is the chemical formula for methane?
CH4
What is an example of a commercial use for an explosion?
Airbags
What is five-minute epoxy?
A product that contains 2 chemicals that when mixed hardens in 5 minutes
How does 5 minute epoxy work?
The molecules have several places where they can join causing it to form one large molecule
What state are metal elements always in?
Solid
Except mercury Hg is liquid
What state are all the diatomic elements?
They are all gases with exceptions:
Br2 is liquid at room temperature since the melting point is -7.2 degrees Celsius and room temperature is above that at 25 degrees celsius, so it is not a solid. In addition, the boiling point of Br2 is 58.8 degrees Celsius, so it is not a gas at room temperature since room temperature is lower than it’s boiling point.
I2 is either liquid or solid in chemical equations. At room temperature it is solid since it does not melt until 113.7 degrees celcius. 113.7 degrees Celsius is melting point. 184.3 degrees celcius is the boiling point.
Hydrogen, nitrogen, oxygen, fluorine, and chlorine are all gases at room temperature. As such, they are called diatomic gases or elemental gases.Bromine is typically a liquid at room temperature, and iodine is solid (but can be liquid depending on several factors)
Some other elements can form diatomic molecules, but the bonds are very weak and unstable. They don’t stay diatomic for long.
Only the seven diatomic elements form strong bonds and appear in this form almost always
What are diatomic elements?
Elements that come in pairs such as O2
Use polyatomic for more than two such as Se8
What state does bromine come in?
Liquid
What state does Iodine come in?
Solid
What do letters in subscript within brackets indicate in a chemical equation?
The state of an element
What does a subscript of (aq) mean?
It is dissolved in water
What state are all ionic compounds?
Solid
When is an ionic compound shown as aqueous?
When it is very soluble and dissolved in water. Use the solubility chart to look up if it is soluble in water. If it is very soluble then it will be marked as aqueous providing that water is actually there during the experiment.
When is an ionic compound shown as solid?
When it is only slightly soluble even if it’s in water
How do you predict the state of molecular compounds?
The smaller the molecules means most likely gas. The bigger the molecules most likely solid
What are exothermic reactions?
When chemical reactions releases energy in the form of heat, light, or electricity
How do car batteries work? What are the chemicals involved?
They contain sulfuric acid (H2SO4(aq)) which is a strong electrolyte which reacts with solid lead (Pb(s)) and lead (IV) oxide (PbO2(s)) to produce electricity.
The products of this reaction are lead(II) sulfate in solution and water
PbO2 is solid, dark brown, has a crystalline structure, and is insoluble in water.
This is an example of an acid and a metal reacting. It is also an example of a double replacement reaction and thus it must be occurring in solution since all double replacement reactions must occur in solution. It is a neutralization reaction as well since an acid is a reactant and a salt and water are produced.
What is a combustion reaction?
When oxygen reacts with a substance to form a new substance and gives off energy.
How is electricity made using combustion?
Coal is burned and the steam used to burn the coal is able to turn a turbine. Then the turning motion can operate a generator creating electricity.
What is a reactant in a combustion reaction?
Oxygen
What are the products of a combustion reaction?
Carbon dioxide (or element dioxide), energy, and water vapor
What are the fossil fuels?
Coal, Oil, and natural gas
What is gasoline made out of?
Hexane C6H14
What are endothermic reactions?
Reactions that absorb energy
What are biochemical reactions essential to?
Life
What are catalysts?
Chemicals that speed up a reaction but are not used up by it
What are biochemical reactions?
Reactions that happen at an organism’s body temperature and are sped up by catalysts
What type of reaction is synthesis? Is it endothermic or exothermic?
Bringing two or more atoms together.
Endothermic
Photosynthesis is a synthesis reaction
If energy is on the left side of chemical reaction is it endothermic or exothermic?
Endothermic
If energy is on the right side of a reaction is it exothermic or endothermic?
Exothermic
What type of reaction is cellular respiration?
Exothermic
What are the characteristics of chemical reactions?
- Production of new substances
- Flow of energy
- Change of state (but not solely a traditional phase change, just it happens due to the properties of the new substance or because something heated up or cooled down as a result of a chemical reaction)
- Consistent with the law of conservation of mass
What comes along with a formation of a new substance?
New properties of state, melting point, color, density
How can the flow of energy be detected?
-A change in temperature during the reaction
What is the law of conservation of mass?
States that in a chemical reaction matter cannot be created or destroyed
What does the arrow mean when writing a chemical formula?
Produces
What is a formula equation?
Uses the chemical formulas of the reactants and products in a chemical reaction
What is a skeletal equation?
A formula that shows the different elements but not in the correct proportions
What are coefficients?
Numbers placed in front of elements or compounds to put in proper proportions
What are the 5 common types of chemical reactions?
- Formation reactions
- Decomposition reactions
- Hydrocarbon combustions
- Single replacement
- Double replacement
What is another name for a formation reaction?
Synthesis
What takes place in a formation reaction?
2 elements combine to form a compound
What is a decomposition reaction?
When a compound is broken down into its different parts. Only 1 reactant
What are hydrocarbons?
Substances that contain hydrogen and carbon
What is hydrocarbon combustion?
When hydrogen and carbon mix with oxygen and burn producing carbon dioxide and water vapor
What is the chemical formula for natural gas?
There isn’t one formula since natural gas is not a pure substance. However, CH4 (methane) is the primary constituent of natural gas
Some ethane, propane, as well as heavier hydrocarbons, water, carbon dioxide, nitrogen, hydrogen sulfide
What is a single replacement reaction?
When a reactive element reacts with an ionic compound. After the reaction, the element ends up in a compound and an element ends up by itself
What is a double replacement reaction?
When 2 ionic compounds switch elements
What kind of chemical reaction can only take place in a solution?
Double replacement reactions
What is the mole?
The unit mole is the measure chemists use to measure the quantity of elements
1 mol = avogadro’s constant amount of particles
What is the number of particles in one mole called?
Avogadro’s number
What element do chemists use to define the mole?
Carbon-12
What number is Avagadro’s number?
6.02 x 10^23
What is the formula for finding the atomic molar mass?
M = m/n
m = nM
M molar mass found on the periodic table
m actual mass in the experiment
n actual moles in the experiment
What does m mean when finding the atomic molar mass?
The mass in grams
What does n mean when finding the atomic molar mass?
The number of moles
What does M mean when finding the atomic molar mass?
The molar mass,
find it on the periodic table
All about combustion reactions
