Chemistry: Chemical reactions

For Test

Name the 3 types of energy transfer and briefly describe each. Name one example each.

• Radiation: Radiation is the transfer of heat energy through space by electromagnetic radiation.

• Conduction: Conduction is the transfer of heat energy from one substance to another or within a substance.

• Convection: Convection is the transfer of heat energy in a fluid or gas. This type of heating is most commonly seen in the kitchen with a boiling liquid.

Radiation examples:

• Ultraviolet light from the sun

• A burning candle emits radiation in the form of heat and light

• Radio waves, microwaves, visible light, Lasers, etc

Conduction examples:

• A lizard warming its belly on a hot rock

• The heat from a stovetop transferring into a metal pot of water

• A blacksmith heating up a sword in hot coals, and the heat transferring up through the metal

Convection examples:

• Boiling water (heats up, gets less dense, floats to the top of the pot and is replaced with cold water)

• Fire heating up air - air expands, loses density, rises

• Sea or land breeze caused by difference in pressure

Describe an extreme weather condition and relate this to global warming. Why is the phenomenon getting worse with higher temperatures?

A warming climate can increase the risk of both submarine (underwater) and aerial (above ground) landslides, thereby increasing the risk of local tsunamis. The melting of permafrost (frozen soil) at high latitudes decreases soil stability, making it more susceptible to erosion and landslides

What is needed for a combustion reaction to take place? What are the products?

Reactants: Oxygen, heat (energy), fuel

Products: CO2 + H20

Exothermic reaction:

Exothermic process releases heat (energy) into its surroundings

On graph: Up to down

Endothermic reaction:

Endothermic process absorbs heat (energy) from its surroundings in order to take place

On graph: Down to up

Exothermic reaction examples:

• Burning of a Candle

• Burning of Sugar

• Creation of an ice cube (water → ice)

Endothermic reaction examples:

• Melting of an ice cube (ice → water)

• Cooking an egg

• evaporation

Is a combustion reaction exothermic or endothermic?

Exothermic

Explain why the mass of ash in a combustion reaction is less than the mass of wood. Does this observation show that the Law of conservation of mass is false?

the oxygen was torn off of the wood and burned, this means a lot of the wood dispersed into the surrounding area. The ash is simply the leftovers. No mass was destroyed, simply transmuted

Name the 5 types of chemical reactions

• Synthesis

• Decomposition

• Single replacement

• Double replacement

• Combustion

Synthesis

A + B → AB

Decomposition

AB → A + B

Single Displacement

A + BX → AX + B

Double Displacement

AB + XY → AX + BY

Combustion

Carbon Compound + O2 → CO2 + H2O

Double Displacement

Single Displacement

Combustion

Synthesis

Describe the difference between an exothermic and endothermic reaction

An exothermic process releases heat, causing the temperature of the immediate surroundings to rise. An endothermic process absorbs heat and cools the surroundings.

When ammonium chloride is added to water, a chemical reaction takes place and the temperature decreases. Is the reaction endothermic or exothermic?

Endothermic because it dissolves

Endothermic reactions in medicine or technology:

• Ice pack

• Baking cake

Exothermic reactions in medicine or technology:

• Fuel combustion in planes

• Burning coal in a forge

Molar Mass abbreviation:

M

Mass abbreviation:

m

Mole abbreviation:

n

Unit for molar mass:

g/mols

Unit for Mass:

grams

Unit for Moles:

Mols and/or Moles

m = ?

m = n x M

n = ?

n = m/M

M = ?

M = m/n