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