Question

4. When baking soda is mixed with lemon juice, bubbles are formed with

the evolution of a gas. What type of change is it? Explain.

5. When a candle burns, both physical and chemical changes take place.

Identify these changes. Give another example of a familiar process in

which both the chemical and physical changes take place.

6. How would you show that setting of curd is a chemical change?

7. Explain why burning of wood and cutting it into small pieces are

considered as two different types of changes.

8. Describe how crystals of copper sulphate are prepared.

9. Explain how painting of an iron gate prevents it from rusting.

10. Explain why rusting of iron objects is faster in coastal areas than in

deserts.
pls help guys​

Answer 1

4 CHEMICAL change

we cant make baking soda and lemon juice from it.

and carbon dioxide is formed.

5 chemical change burning of thread and

   physical change melting of wax

similar process is boiling of rice

     chemical change boiling of rice

     physical change evaporation of water.

6 in setting of curd the bacteria converts the lactose present in milk into lactic acid.

7 burning of wood is considered as chemical change because the wood changes to ashes but the cutting into small pieces is physical change because it is wood only.

8 i reaily dont know

10 rusting of iron object is faster in coastal areas than desert because in coastal the level of moisture is high in comparison  of desert.

thanks.

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