Chapter U5, Problem 16STP

Interpretation Introduction

Interpretation:

Among the given options, the change that increases the rate of the process needs to be determined.

Concept introduction:

The solubility of sugar in water depends on the temperature of water.

Increase in temperature of water increases the solubility of sugar in it.

Lighting/combustion is a chemical change and increase in surface area of the reactant increases the rate of this chemical change.

Stains can be removed by using detergent.

When iron is kept open, it reacts with atmospheric oxygen and moisture and form iron oxide called rust.

Answer to Problem 16STP

Option (B) crush charcoal into smaller pieces before lighting.

Explanation of Solution

Reason for correct option:

This increases the surface area of the solid reactant and small pieces catch fire faster than the bigger ones.

Hence, this change speeds up the process.

Conclusion

Reasons for incorrect options:

The solubility of sugar in water depends on the temperature of water.

Increase in temperature of water increases the solubility of sugar in it.

But in option (A) cold water is used which slows down the process.

Stains can be removed by using detergent.

In option (C) the amount of detergent is decreased.

If the amount of detergent is decreased, stain removal becomes slow.

When iron is kept open, it reacts with atmospheric oxygen and moisture and form iron oxide called rust.

In option (D), iron nail is kept closed which does not allow the iron nail to react with atmosphere.

Hence, the rusting chemical reaction rate will be decreased.