Chemicals and Chemical Reactions
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Middle School Physical Science › Chemicals and Chemical Reactions
The image shows the particles of a substance in its three states. The kinetic energy of the particles increases as:
the substance changes from a solid to a liquid
the substance changes from a liquid to a gas
both as it changes from a solid to a liquid and when it changes from a liquid to a gas
none of these
Explanation
The answer is "both as it changes from a solid to a liquid and when it changes from a liquid to a gas." As the temperature of a substance increases, so does the kinetic energy of particles increases.
Certain types of metals, like gold, are both naturally occurring and can be created in a lab. (This process is not used often because it is expensive and not efficient!) This tells us what about metals like gold?
gold is only a synthetic material
gold is only a natural resource
gold is a natural resource that can sometimes be synthetic
gold is not a natural resource or a synthetic material
Explanation
The answer is "Gold is a natural resource that can sometimes be synthetic." Some substances can be either natural or synthetic and it depends on how the substance was made.
Which of these is NOT an example of a chemical reaction?
iron being filed down and turned into powder
lighting a match
plants undergoing photosynthesis
washing your hands with soap
Explanation
In a chemical change, the chemical bonds in the molecules break. The atoms then link together to form new molecules. The types of molecules in matter before and after a chemical change are always different. For example, burning a piece of paper is a chemical change. As paper burns, paper molecules react with oxygen molecules in the air. This reaction breaks the chemical bonds in the molecules. The atoms then relink and form different molecules. For example, carbon dioxide molecules are created when paper burns. Also, once a paper burns you can't get the original piece of paper back. When something can't go back to the original state (or object) this likely means a chemical change has occurred.
The answer is "iron being filed down to a powder" because the metal is undergoing a physical change and its chemical identity stays the same.
Combustibility, toxicity, PH, reactivity, ability to rust, and flammability are all examples of:
chemical properties
physical properties
both chemical and physical properties
none of these
Explanation
The answer is "chemical properties" because they are all observable in chemical changes.
The image shows the particles of a substance in its three states. The kinetic energy of the particles increases as:
the substance changes from a solid to a liquid
the substance changes from a liquid to a gas
both as it changes from a solid to a liquid and when it changes from a liquid to a gas
none of these
Explanation
The answer is "both as it changes from a solid to a liquid and when it changes from a liquid to a gas." As the temperature of a substance increases, so does the kinetic energy of particles increases.
Which of these is NOT an example of a chemical reaction?
iron being filed down and turned into powder
lighting a match
plants undergoing photosynthesis
washing your hands with soap
Explanation
In a chemical change, the chemical bonds in the molecules break. The atoms then link together to form new molecules. The types of molecules in matter before and after a chemical change are always different. For example, burning a piece of paper is a chemical change. As paper burns, paper molecules react with oxygen molecules in the air. This reaction breaks the chemical bonds in the molecules. The atoms then relink and form different molecules. For example, carbon dioxide molecules are created when paper burns. Also, once a paper burns you can't get the original piece of paper back. When something can't go back to the original state (or object) this likely means a chemical change has occurred.
The answer is "iron being filed down to a powder" because the metal is undergoing a physical change and its chemical identity stays the same.
Combustibility, toxicity, PH, reactivity, ability to rust, and flammability are all examples of:
chemical properties
physical properties
both chemical and physical properties
none of these
Explanation
The answer is "chemical properties" because they are all observable in chemical changes.
Certain types of metals, like gold, are both naturally occurring and can be created in a lab. (This process is not used often because it is expensive and not efficient!) This tells us what about metals like gold?
gold is only a synthetic material
gold is only a natural resource
gold is a natural resource that can sometimes be synthetic
gold is not a natural resource or a synthetic material
Explanation
The answer is "Gold is a natural resource that can sometimes be synthetic." Some substances can be either natural or synthetic and it depends on how the substance was made.
The particles in the image on the far left most likely:
belong to a solid and are not moving at all
belong to a solid and are vibrating in place
belong to a liquid that is not moving in a container
belong to a gas that is fit very tightly in a container
Explanation
The answer is "belong to a solid and are vibrating in place." The image shows that the particles are 'stuck together' in a solid configuration. These particles do have kinetic energy so they are vibrating and not completely lacking movement.
Heating Zinc Chloride to its melting point of 290 °C and watching it turn to a liquid is an example of:
a physical change
a chemical change
both a physical and chemical change
neither a physical nor a chemical change
Explanation
In a chemical change, the chemical bonds in the molecules break. The atoms then link together to form new molecules. The types of molecules in matter before and after a chemical change are always different. For example, burning a piece of paper is a chemical change. As paper burns, paper molecules react with oxygen molecules in the air. This reaction breaks the chemical bonds in the molecules. The atoms then relink and form different molecules. For example, carbon dioxide molecules are created when paper burns. Also, once a paper burns you can't get the original piece of paper back. When something can't go back to the original state (or object) this likely means a chemical change has occurred.
In a physical change, chemical bonds do not break. The types of molecules in matter before and after a physical change are always the same. A change of state is a type of physical change. For example, ice melting is a physical change. Ice and water are made of the same thing: water. You can also re-freeze melted water back to ice. When something can go back to the original state (or object) this likely means a physical change has occurred.
The answer is "a physical change" because the chemical composition of Zinc Chloride does not change as its melting.