this is my homework just give the answer already!
Cleaning a penny with vinegar and salt is a chemical change. The vinegar (acetic acid) reacts with the salt (sodium chloride) to form a chemical compound that removes the tarnish on the copper surface of the penny. This reaction changes the composition of the penny's surface, making it appear shiny and clean.
Physical change
Yes, the darkening of a copper penny is a chemical change. When copper is exposed to air and moisture, it reacts with oxygen and carbon dioxide, leading to the formation of copper oxide and other compounds that give the penny a darker appearance. This process alters the chemical composition of the copper, indicating a chemical change rather than a physical one.
chemical, because when a penny is tarnished its a chemical change because, its weathered down its destroyed. The tarnish itself is usually either the oxide and/or sulfide of the underlying metal.
If you use a abrasive to scrape the rust off, then it is a physical change. If you utilize a chemical that combines with the rust leaving the unoxidized penny behind, then it is a chemical change.
Cleaning a penny with vinegar and salt is a chemical change. The vinegar (acetic acid) reacts with the salt (sodium chloride) to form a chemical compound that removes the tarnish on the copper surface of the penny. This reaction changes the composition of the penny's surface, making it appear shiny and clean.
Chemical
Physical change
Putting a penny in lemon juice would cause a chemical change because the lemon juice reacts with the copper in the penny to create copper oxide, which changes the chemical composition of the penny.
Chemical.
It is a physical change, because it does not change in substance. A penny, whether in its normal state or flattened, is still a penny. Similarly, if you drop a watermelon and it breaks apart, that is also considered to be a physical change because it is still a watermelon. Things are considered to be chemical changes when the substance changes into something new, and is commonly classified as irreversible. When an object rusts, it is considered to be a chemical change. Chemical changes are associated with a temperature change, or a color change or bubbling or something of the sort. Physical changes deal with physical changes in state, for example, ice melting, or in the example you provided, a penny being flattened.
Removing tarnish from a penny with salt and vinegar is a chemical change. The reaction between the salt, vinegar, and tarnish on the penny results in the formation of new substances that remove the tarnish.
Yes
Turning a penny gold is a physical reaction rather than a chemical reaction. This process involves coating the penny with a layer of gold, which changes its appearance but does not alter the chemical composition of the penny itself.
chemical, because when a penny is tarnished its a chemical change because, its weathered down its destroyed. The tarnish itself is usually either the oxide and/or sulfide of the underlying metal.
A physical change is when some thing's shape or volume is changed. But a chemical change is a reaction between two or more objects to create something new and you can't get back what you originally started with.
It depends how you mean dull. Dull by wear or dull by oxidation? If it just becomes dull without being touched, then it is a chemical change. Metals readily react with non metals ie Oxygen. This will form a metal oxide layer on the exposed regions. This is why you need to sandpaper down some of the more reactive metals, when using them for conductivity experiments in school, as the oxide reduces conductivity.