MAT-2 chemistry quiz
examples of chemical change on macroscopic level:
- calcium chloride reacting with sodium bicarbonate resulted in bubbles - burned wood produces both heat and light
There are some key observations to look for in order to identify a chemical change on the _______. While these observations may be _________.
- macroscopic level - evidence of a chemical change they do not always mean a chemical change has occurred.
By heating or cooling a sample of matter, it can change from _________. This is called a _______.
- one state to another - phase change
choose a phase change and answer the question: change a:
- salt water being heated (evaporation)
we know that matter can change forms through physical and chemical changes, but through any of these changes matter is always conserved. The same amount of matter exists before and after the change-none is created or destroyed. Example: If 1 kg of ice is melted, then the liquid water would still have a mass of:
1 kg
2 choices of types of particles when drawing mixture particle diagram:
1. atoms 2. molecules
ways you can recognize a chemical change on the macroscopic level:
1. production of a gas 2. production of a solid (or precipitate) 3. production of light 4. temperature change 5. color change
what are some ways in which you can recognize a chemical change on the macroscopic level?
1. production of heat/light 2. production of gas 3. production of a solid (from 2 liquids) 4. color change 5. temperature change
2O₂
2 molecules of oxygen gas
oxygen (______)
2O₂
there are ____ different changes in state that we need to know.
6
CH₄:
C: element carbon H: element hydrogen 4: 4 hydrogen atoms for every carbon atom in the substance.
CO₂:
C: one carbon atom O₂: 2 oxygen atoms
methane (______)
CH₄
carbon dioxide (______)
CO₂
Phase change: condensation Initial state: _____ Final state: _______ Heated/cooled: _______ energy: _______
Initial state: gas Final state: liquid Heated/cooled: cool energy: out
Phase change: deposition Initial state: _____ Final state: _______ Heated/cooled: _______ energy: _______
Initial state: gas Final state: solid Heated/cooled: cool energy: out
Phase change vaporization: Initial state: _____ Final state: _______ Heated/cooled: _______ energy: _______
Initial state: liquid Final state: gas Heated/cooled: heat energy: into
Phase change freezing: Initial state: _____ Final state: _______ Heated/cooled: _______ energy: _______
Initial state: liquid Final state: solid Heated/cooled: cool energy: out
Phase change: sublimation Initial state: _____ Final state: _______ Heated/cooled: _______ energy: _______
Initial state: solid Final state: gas Heated/cooled: heat energy: in
Phase change melting: Initial state: _____ Final state: _______ Heated/cooled: _______ energy: _______
Initial state: solid Final state: liquid Heated/cooled: heat energy: into
change b: draw a particle representation of the starting matter and then the final state of matter:
It's a mixture so I used different colors to represent different components (not independent atoms)
here is the phase diagram for water. it is a graph of pressure (atm) vs temperature (°C) showing the phase (or state) of water under different conditions. Normal atmospheric pressure is 1 atm. Using this information, answer the following questions. a. what is indicated by the specific line marked B on the graph? Explain
Line B represents the freezing (or melting) point of water because this line separates the conditions where H2O will exist as a solid from those where it will exist as a liquid.
Example of phase change classified as endothermic:
Melting is an endothermic change because the solid would need to absorb energy in order to become a liquid
explain the difference between a physical and a chemical change.
a physical change is one in which the chemical make up does not change, but in a chemical change it does.
choose two of the examples from #8 above and explain what you would expect to observe on the macroscopic level for these changes. What specific evidence might you observe for that type of change? Be as specific as possible. Think about what you learned about properties of the different types of matter and their changes in the lab.
a. when water decomposes, I would to observe a liquid producing 2 different gases with different chemical properties because 2 new molecules were formed. d. when the 3 metals are combined to make a gold ring, I would expect that the metals would retain their individual chemical properties because no new particles were formed and the color of the ring would be a combination of the 3 metals.
When bonds are broken, energy is _____
absorbed
Depending on the difference in energy between the 2 processes (bonds breaking/bonds forming), energy will either be:
absorbed or released overall
change b: explain the behavior of the particles on the sub-microscopic level AFTER the change occurs"
after freezing, the particles are in a solid state so they are arranged close together in a regular pattern and they only vibrate in place. They now have less energy in the solid state.
we know that matter can change forms through physical and chemical changes, but through any of these changes matter is:
always conserved
change a: explain what is happening to the particles on the sub-microscopic level WHILE the change is occurring.
as the phase change is taking place, the H2O molecules are gaining energy because the beaker is heated. As they gain energy, they will move around more and move faster. (endothermic)
change b: explain what is happening to the particles on the sub-microscopic level WHILE the change is occurring.
as the phase change is taking place, the liquid particles are losing energy so they are slowing down and moving around less. They are coming together in a set pattern.
we know that matter can change forms through physical and chemical changes, but through any of these changes matter is always conserved. The same amount of matter exists:
before and after the change-none is created or destroyed.
In order for the atoms to rearrange in a chemical change:
bonds have to be both broken and formed
examples of chemical changes:
burning wood, iron rusting, oxygen catching on fire
If we look at the chemical reaction between methane and oxygen to form carbon dioxide and water, we can clearly see that the number of oxygen atoms on the left side (4 oxygen) is equal to the number of oxygen atoms on the right side (4 oxygen). The same is true for the _____ and _________.
carbon and hydrogen atoms
all changes in matter also involve:
changes in energy
physical or chemical change: a banana turns from yellow to brown
chemical
physical or chemical change: a firecracker explodes
chemical
physical or chemical change: acid in tomato sauce corrodes aluminum foil
chemical
physical or chemical change: silver tarnishes when it comes in contact with hydrogen sulfide in the air.
chemical
physical or chemical change: a glow stick gives off light
chemical change
physical or chemical change: a match burns
chemical change
physical or chemical change: calcium chloride reacts with sodium bicarbonate in phenol red
chemical change
physical or chemical change: the milk smells sour
chemical change
physical or chemical change: the statue of liberty turned green over time
chemical change
when drawing particle diagram for a mixture that is a liquid, the particles should be:
close together and pointing in different directions
methane is a:
compound
identify the type of phase change: there is a puddle of liquid on your desk under your cold drink
condensation
If we look at the chemical reaction between methane and oxygen to form carbon dioxide and water, we can clearly see that the number of oxygen atoms on the left side (4 oxygen) is equal to the number of oxygen atoms on the right side (4 oxygen). Therefore, matter is:
conserved on the atomic level
Changes that are endothermic tend to feel:
cool and a decrease in temperature can be measured
identify the type of phase change: frost forms on a car windshield
deposition
Those chemical changes that absorb energy are classified as:
endothermic
identify each change as an endothermic and an exothermic: ice melting
endothermic
identify each change as an endothermic and an exothermic: sodium bicarbonate dissolves in water and the beaker feels cool
endothermic
identify the type of phase change: a beaker of salt water is heated and the water in the beaker decreases
evaporation
Those chemical changes that release energy are classified as:
exothermic
identify each change as an endothermic and an exothermic: magnesium reacts with hydrochloric acid and the test tube feels warm.
exothermic
identify each change as an endothermic and an exothermic: making ice cubes
exothermic
explain the difference between an endothermic and exothermic change.
for an endothermic change, heat is absorbed, where as heat is released during an exothermic change
we know that matter can change:
forms through physical and chemical changes
identify the type of phase change: a smoothie is placed in the freezer and turns solid
freezing
Example of phase change classified as exothermic:
freezing is an exothermic change because energy is released
change a: explain the behavior of the particles on the sub-microscopic level BEFORE the change occurs.
in the liquid water, the particles are close together, but free to move around so there is no set pattern and the particles will conform to the shape of the beaker. the water molecules have a moderate amount of energy.
Antoine and Marie built their own:
instruments in order to make detailed measurements.
here is the phase diagram for water. it is a graph of pressure (atm) vs temperature (°C) showing the phase (or state) of water under different conditions. Normal atmospheric pressure is 1 atm. Using this information, answer the following questions. b. the freezing point of water is usually cited as 0°C, but is that true under all conditions. Is it possible to change the freeing point of water? Explain using the graph.
looking at the graph you can see that the freezing point of H2O is only 0°C at 1 atm, which is normal atmospheric pressure. If the pressure changes, then the freezing point will change. As the P increases, the freezing point will decrease.
In the late 1700's French chemist Antoine Lavoisier and his wife Marie Lavoisier performed:
many careful science experiments
identify the type of phase change: a popsicle melts when eaten outside
melting
examples of physical changes:
melting ice, breaking sugar cubes, recycling plastic
change a: explain the behavior of the particles on the sub-microscopic level AFTER the change occurs"
once the molecules are fully in the gas phase, they will move around randomly and rapidly to conform to the shape and volume of their container. They now have a high amount of energy.
We can also classify ________ as exothermic or endothermic.
phase changes
physical or chemical change: a bar of lead is easily bent
physical
physical or chemical change: a diamond scratches glass.
physical
physical or chemical change: a sheet of copper is pounded into a bowl.
physical
physical or chemical change: barium melts at 725 degrees C
physical
physical or chemical change: a popsicle melts in the sun
physical change
physical or chemical change: a test tube breaks
physical change
physical or chemical change: nail polish hardens
physical change
physical or chemical change: sodium chloride is dissolved in water
physical change
all changes in state are classified as:
physical changes
When bonds are formed, energy is ________
released
change b: explain the behavior of the particles on the sub-microscopic level BEFORE the change occurs.
same description as "BEFORE" on page. 43 but lots of different types of molecules.
choose a phase change and answer the question: change b:
smoothie in the freezer (freezing)
We can also follow the Law of Conservation of matter on a:
sub-microscopic level
identify the type of phase change: solid dry ice appears to disappear when placed on a lab bench
sublimation
the Law of Conservation of Matter states:
that during any physical or chemical change, matter is neither created nor destroyed.
For Antoine and Marie's work, they determined that:
that the mass of the starting materials was always equal to the mass of the final products
If we look at the chemical reaction between methane and oxygen to form carbon dioxide and water, we can clearly see:
that the number of oxygen atoms on the left side (4 oxygen) is equal to the number of oxygen atoms on the right side (4 oxygen)
Today, Antoine and Marie's idea is known as:
the Law of Conservation of Matter
a chemical change occurs when:
the atoms of 1 or more substances are rearranged resulting in a new substance with new properties.
a physical change occurs when:
the substance changes state or form, but without a change in chemical composition.
macroscopic:
these are you experiences and the processes you observe. It includes you qualitative and quantitative observations
Changes that are exothermic tend to feel:
warm and an increase in temperature can be measured
We can also classify phase changes as exothermic or endothermic based on:
whether energy is absorbed or released when the change of state occurs.
