Melting and boiling temperatures of different substances

In summary, the conversation discusses a question on a practice physics exam that asks which substance is a gas at 25 C. The provided table lists the melting and boiling temperatures of four substances and the conversation explains that a solid melts at its melting point and becomes a liquid, while a liquid boils at its boiling point and becomes a gas. The answer to the question is "A" and the person asking for help thanks the responder.
  • #1
riyada
3
0
Hi all
I am sorry for the double post, I just found out there is a homework help place here..
I have this question in a practice physics exam:
The table lists melting and boiling temperatures of 4 different substances, A,B,C,D..
The question is "Which substance is a gas at 25 C?"

Substance Melting point /C Boiling point/C
A -219 -183
B -7 58
C 98 890
D 1083 2582

I have no idea how to get the answer.. Can someone please explain how..
Thanks!
 
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  • #2
Welcome to PF!

riyada said:
The table lists melting and boiling temperatures of 4 different substances, A,B,C,D..
The question is "Which substance is a gas at 25 C?"

Substance Melting point /C Boiling point/C
A -219 -183
B -7 58
C 98 890
D 1083 2582

Hi riyada! Welcome to PF! :smile:

A solid melts at its own melting point, and becomes a liquid.

A liquid boils at its own boiling point, and becomes a gas.

The question gives you the melting point and the boiling point of four substances. :smile:
 
  • #3
Beautifully answered!
Its "A"..
Thanks a MIL!
 

1. What is the difference between melting and boiling temperatures?

Both melting and boiling temperatures refer to the point at which a substance changes from one phase to another. Melting occurs when a solid turns into a liquid, while boiling occurs when a liquid turns into a gas. The main difference between the two is the amount of energy required to reach these temperatures. Melting temperatures are typically lower than boiling temperatures.

2. How are melting and boiling temperatures determined?

Melting and boiling temperatures are determined by the chemical makeup and structure of a substance. Each substance has a unique set of intermolecular forces, which determine how tightly its molecules are held together. The stronger the intermolecular forces, the higher the melting and boiling temperatures will be.

3. Why do different substances have different melting and boiling temperatures?

As mentioned before, the chemical structure and intermolecular forces of a substance play a major role in determining its melting and boiling temperatures. For example, substances with stronger intermolecular forces, such as metals, will have higher melting and boiling temperatures compared to substances with weaker intermolecular forces, such as non-metals.

4. Can melting and boiling temperatures change?

Yes, melting and boiling temperatures can change depending on external factors, such as pressure and impurities. Changes in pressure can affect the intermolecular forces and therefore alter the melting and boiling temperatures. Impurities can also disrupt the intermolecular forces and result in a lower melting or boiling temperature.

5. How do melting and boiling temperatures affect everyday life?

Melting and boiling temperatures play a crucial role in many everyday activities, such as cooking, heating, and cooling. For example, knowing the melting and boiling temperatures of different substances helps us determine the best way to cook and preserve food. It also allows us to control the temperature of our homes and appliances, making our lives more comfortable and convenient.

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