5.1 Chemistry Essay
5.1 Homework PG178
Questions: 2, 3, 5, 8, 9
2. Classify each of the following observations as an example of either a chemical or physical property
a. Liquid nitrogen boils at -198˚C This is a physical property because it is a matter of changing state.
b. Propane leaking from a damaged tank, ignites easily This is a chemical property because it is flammable.
c. Silver jewelry tarnishes (darkens) in air This is a chemical property because the silver becomes dark because of oxygen
d. Spilled oil generally floats on the surface of water This is a physical property because it does not mix to create a new substance
e. Meat darkens when it is heated on a grill This is a chemical property because something new is created.
f. Sulfuric trioxide …show more content…
changes to sulfuric acid in the atmosphere This is a chemical property because a new substance (sulfuric acid is created) 3.
What kind of change is described in each of the following situations? Justify your answer.
a. Air is often blended into ice-cream to give a lighter texture
This is a physical change. This is because there is no new substance created. The change only takes place in the ice-cream and nothing new is created. The ice cream still stays ice-cream .
b. When popping corn is heated, water inside the kernels becomes gas and expands. This creates enough pressure to explode the kernel.
This is a physical change because there is no new substance created. There is only change in state in where the water has been expanded into gas, but the corn still remains the same and therefore it is a physical change.
c. A loud pop is heard when a lit match is placed at the mouth of a test tube containing hydrogen gas.
This is an example of a chemical change because there is a new gas that has formed. In this case, the new gas is hydrogen, and hydrogen is the reason behind the little pop sound because the reaction of hydrogen and oxygen causes a small explosion that gives a pop sound.
d. Ethanol is used as an alternative source of energy to power …show more content…
vehicles
It is a chemical change because there is a new substance created. This is because ethanol (an alcohol) is being converted into fuel because it’s mixed with other types of fuels to create a new substance. Therefore it is a chemical change.
e. Geothermal energy from underground hot springs is used to heat water to turn turbines and create electricity
This is a physical change because there is no new substance created.
The only thing that has changed is the energy turning into electricity, but otherwise the heat energy is still energy. 5. Over time crusty scales form on the heating coil inside a kettle. These can be removed by covering it with vinegar. As the scales disappear, bubbles of gas are observed. Is this a chemical change or a physical change?
Using vinegar to take off crusty scales is an example of a chemical change. This is because when using vinegar a new substance is formed. In this case the new substance is a gas. Another reason why we know that it is a chemical change is because bubbles are noticed This immediately tells us that it is a chemical change and not physical. 8. Drain cleaners often produce a great deal of heat when used. Is this action a chemical or physical change?
Using a drain cleaner to clear clogs is a chemical change. This is because it creates a new substance. The reason behind the production of heat is because drain cleaners also follow the process of giving and taking electrons depending on the clogged material. Therefore with reactions happening between atoms a new substance is created, therefore making it a chemical
change. 9. Adding vinegar to milk creates small lumps called curds to form in the milk. Is this a physical or chemical change?
Creating small lumps of curds is a chemical change. This is because you are creating a new substance which in this case is, called curds. The reason for this to be created is because the sugar lactose in the milk reacts with the vinegar to create small curds and because this is a new substance it is a chemical change.
Questions: 2, 3, 5, 8, 9
2. Classify each of the following observations as an example of either a chemical or physical property
a. Liquid nitrogen boils at -198˚C This is a physical property because it is a matter of changing state.
b. Propane leaking from a damaged tank, ignites easily This is a chemical property because it is flammable.
c. Silver jewelry tarnishes (darkens) in air This is a chemical property because the silver becomes dark because of oxygen
d. Spilled oil generally floats on the surface of water This is a physical property because it does not mix to create a new substance
e. Meat darkens when it is heated on a grill This is a chemical property because something new is created.
f. Sulfuric trioxide …show more content…
changes to sulfuric acid in the atmosphere This is a chemical property because a new substance (sulfuric acid is created) 3.
What kind of change is described in each of the following situations? Justify your answer.
a. Air is often blended into ice-cream to give a lighter texture
This is a physical change. This is because there is no new substance created. The change only takes place in the ice-cream and nothing new is created. The ice cream still stays ice-cream .
b. When popping corn is heated, water inside the kernels becomes gas and expands. This creates enough pressure to explode the kernel.
This is a physical change because there is no new substance created. There is only change in state in where the water has been expanded into gas, but the corn still remains the same and therefore it is a physical change.
c. A loud pop is heard when a lit match is placed at the mouth of a test tube containing hydrogen gas.
This is an example of a chemical change because there is a new gas that has formed. In this case, the new gas is hydrogen, and hydrogen is the reason behind the little pop sound because the reaction of hydrogen and oxygen causes a small explosion that gives a pop sound.
d. Ethanol is used as an alternative source of energy to power …show more content…
vehicles
It is a chemical change because there is a new substance created. This is because ethanol (an alcohol) is being converted into fuel because it’s mixed with other types of fuels to create a new substance. Therefore it is a chemical change.
e. Geothermal energy from underground hot springs is used to heat water to turn turbines and create electricity
This is a physical change because there is no new substance created.
The only thing that has changed is the energy turning into electricity, but otherwise the heat energy is still energy. 5. Over time crusty scales form on the heating coil inside a kettle. These can be removed by covering it with vinegar. As the scales disappear, bubbles of gas are observed. Is this a chemical change or a physical change?
Using vinegar to take off crusty scales is an example of a chemical change. This is because when using vinegar a new substance is formed. In this case the new substance is a gas. Another reason why we know that it is a chemical change is because bubbles are noticed This immediately tells us that it is a chemical change and not physical. 8. Drain cleaners often produce a great deal of heat when used. Is this action a chemical or physical change?
Using a drain cleaner to clear clogs is a chemical change. This is because it creates a new substance. The reason behind the production of heat is because drain cleaners also follow the process of giving and taking electrons depending on the clogged material. Therefore with reactions happening between atoms a new substance is created, therefore making it a chemical
change. 9. Adding vinegar to milk creates small lumps called curds to form in the milk. Is this a physical or chemical change?
Creating small lumps of curds is a chemical change. This is because you are creating a new substance which in this case is, called curds. The reason for this to be created is because the sugar lactose in the milk reacts with the vinegar to create small curds and because this is a new substance it is a chemical change.