What are the answers to the following multiple choice and fill-in-the-blank questions about basic science concepts?

Here are the answers to the questions:

Multiple Choice Questions:

1. Plants make their own food in the presence of:

   • d. all of these
   • Plants require sunlight, water, and carbon dioxide for photosynthesis.

2. Rusting of iron can be prevented by:

   • a. galvanisation
   • Galvanisation involves coating iron with a layer of zinc to prevent rust.

3. Melting of butter is which kind of change:

   • a. physical
   • Melting is a change of state, where the butter changes from solid to liquid but its chemical composition remains the same.

4. During exothermic chemical reactions heat is:

   • a. released
   • Exothermic reactions are characterized by the release of heat energy.

5. Which gas is formed when Baking Soda and Vinegar reaction.

   • d. Carbon dioxide
   • The reaction between baking soda (sodium bicarbonate) and vinegar (acetic acid) produces carbon dioxide gas.

Fill in the blanks:

1. Chemical changes are usually irreversible in nature.

   • Chemical changes result in new substances and are generally not reversible.

2. The process of crystallization involves cooling of a saturated solution.

   • Crystallization is the process of forming crystals from a saturated solution upon cooling.