IM forces-substances of increasing melting points

In summary, the substances listed in increasing melting point are Cl2, CHF3, H2O, CHCl3, SiO2. The trend in melting points is determined by the strength of intermolecular forces, with SiO2 having the highest melting point due to its giant covalent structure, H2O having hydrogen bonding, and Cl2 having the lowest melting point due to only van der Waals forces. The melting points of CHF3 and CHCl3 are uncertain as they may have hydrogen bonding, but CHF3 is expected to have a higher melting point due to this.
  • #1
joe98
27
0
Q.In which of the answers below are the substances listed in order of increasing melting
point?
a) Cl2 < CHF3 < H2O < CHCl3 < SiO2
b) Cl2 < CHCl3 < CHF3 < H2O < SiO2
c) Cl2 < CHF3 < CHCl3 < H2O < SiO2
d) Cl2 < H2O < CHF3 < CHCl3 < SiO2
e) SiO2 < H2O < CHCl3 < CHF3 < Cl2

How can we tell the melting points of these substances by there intermolecular forces?

ok H20 has hydrogen bonding, SiO2 has strong covalent bonds,CHF3 has dipole forces

So how can develop a trend in melting points with the IM forces?

Any suggestions?

The answer is C
 
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  • #2
SiO2 is a giant covalent structure - a macromolecule so it has the highest melting point
H2O has hydrogen bonding
Cl2 a gas has the lowest melting point as only vanderwaal ofrces exist

I'm not sure about CHCl3 and CHF3 - i though CHF3 will have a higher MP because of hydrogen bonding
 

1. What are IM forces and how do they affect the melting point of substances?

IM forces, or intermolecular forces, are the attractive forces between molecules. They can be divided into three types: London dispersion forces, dipole-dipole interactions, and hydrogen bonding. These forces play a crucial role in determining the melting point of a substance. Generally, substances with stronger IM forces will have a higher melting point, as it takes more energy to break these forces and change the substance from a solid to a liquid state.

2. Why do substances with increasing melting points have stronger IM forces?

The strength of IM forces depends on the polarity and size of the molecules. As the size and polarity of molecules increase, so does the strength of their IM forces. This is because larger molecules have more surface area for interactions between molecules, and polar molecules have regions of positive and negative charge that can attract each other. Therefore, substances with increasing melting points have stronger IM forces due to their larger and more polar molecules.

3. Can we predict the melting point of a substance based on its IM forces?

While there is a general correlation between the strength of IM forces and the melting point of a substance, it is not always possible to predict the exact melting point based on IM forces alone. Other factors such as molecular shape and crystal structure can also affect the melting point. Additionally, the presence of impurities can lower the melting point of a substance, even if it has strong IM forces.

4. How do IM forces differ from chemical bonds in determining melting points?

Chemical bonds, such as covalent and ionic bonds, are much stronger than IM forces and are responsible for holding atoms together in a molecule. Chemical bonds determine the properties of a substance, such as its structure and reactivity. On the other hand, IM forces are weaker and play a role in the physical properties of a substance, such as its melting point. Therefore, while both chemical bonds and IM forces are important in determining the properties of a substance, they have different strengths and functions.

5. Can the melting point of a substance be changed by altering its IM forces?

Yes, the melting point of a substance can be changed by altering its IM forces. By adding or removing functional groups on a molecule, we can change its polarity and size, which will in turn affect the strength of its IM forces. This is commonly seen in the use of additives in polymers, where different functional groups are added to change the properties of the polymer, including its melting point. Additionally, external factors such as pressure and temperature can also affect the strength of IM forces and thus the melting point of a substance.

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