Physical and Chemical Changes

In summary, the conversation is discussing classifying certain actions as physical or chemical changes. The examples given include tarnishing of copper, heating sugar to form caramel, pouring concentrated nitric acid on a copper coin, evaporating a solution of copper sulfate, heating lead nitrate, and adding sodium carbonate and sodium metal to water. The conclusion is that all of these actions are likely chemical changes, with the exception of evaporating a solution of copper sulfate and adding sodium metal to water, which may also be physical changes.
  • #1
Zappa
1
0
This question asks me to classify each of the following as a physical or a chemical change.

a. Tarnishing of copper
b. Heating sugar to form caramel
c. Pouring concentrated nitric acid on a copper coin to form brown fumes
d. Evaporating a solution of copper sulfate to dryness (to form blue crystals)
e. Heating lead nitrate until brown fumes form
f. Adding sodium carbonate to water
g. Adding sodium metal to water

To me they all seem like chemical changes. :confused: The only ones that might not be are d and g, but I'm not really sure.
 
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  • #2
Hey Zappa;

Go to your favorite search engine, type in "Sodium", choose a site, and see what it says about when Sodium is added to water. Good luck.

Best of health.

Steve
 
  • #3


I would classify each of the following as a physical or a chemical change based on the fundamental differences between these two types of changes. A physical change is a change in the physical properties of a substance, such as its shape, size, or state, without altering its chemical composition. On the other hand, a chemical change involves a transformation of the chemical composition of a substance, resulting in the formation of new substances with different properties.

a. Tarnishing of copper - This is a physical change as it only affects the surface appearance of the copper without altering its chemical composition.

b. Heating sugar to form caramel - This is a chemical change as the heat causes the sugar molecules to break down and rearrange into new substances with different properties.

c. Pouring concentrated nitric acid on a copper coin to form brown fumes - This is a chemical change as the nitric acid reacts with the copper to form new substances, including brown fumes of nitrogen dioxide.

d. Evaporating a solution of copper sulfate to dryness (to form blue crystals) - This is a physical change as the water is simply being removed from the solution, leaving behind the same chemical compound with the same properties.

e. Heating lead nitrate until brown fumes form - This is a chemical change as the heat causes the lead nitrate to decompose and form new substances, including brown fumes of nitrogen dioxide.

f. Adding sodium carbonate to water - This is a physical change as the sodium carbonate simply dissolves in water without any chemical reaction taking place.

g. Adding sodium metal to water - This is a chemical change as the sodium reacts with water to form new substances, including hydrogen gas and sodium hydroxide. This reaction is also exothermic, releasing heat and causing the water to boil.
 

1. What is the difference between a physical and chemical change?

A physical change involves a change in the appearance or state of matter, but the substance itself remains the same. A chemical change, on the other hand, involves a change in the chemical composition of a substance, resulting in a new substance being formed.

2. How can you tell if a change is physical or chemical?

Some clues that a change is physical include changes in size, shape, or state of matter. Chemical changes can be identified by the production of gas, a change in color, or the formation of a new substance.

3. What are some examples of physical changes?

Examples of physical changes include melting, freezing, boiling, cutting, and dissolving.

4. What are some examples of chemical changes?

Examples of chemical changes include burning, rusting, digestion, and fermentation.

5. Can a physical change be reversed?

Yes, physical changes can typically be reversed by changing the conditions, such as melting ice back into water. However, chemical changes are not easily reversible and often require a chemical reaction to change the substance back to its original form.

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