Changes around us

classs 6(New Science Ahead)

1. LESSON 7 CHANGES AROUND US

2. Are there changes around us?

3. Weather and temperature change. Softening of vegetables when cooked Drying of wet clothes. Spoilage of food Rusting of iron

4. List out more changes. 1. Change in age 2. Changes in appearance 3. Growth of hair 4. Baking of bread 5. Growth of plants 6. Destruction of forest 7. Condensation and evaporation 8. Pollution of air 9. Falling of leaves 10. Flowering of plant 11. Movements of Earth 12. Changes of seasons

5. All changes in the world are one of the two types – Reversible changes and irreversible changes.

6. Changes that can be easily reversed by removing the cause of change are called a reversible changes .

7. Examples Melting of wax cooling of water boiling of water folding of paper evaporation drying of clothes BLOWING A BALLOON DISOLVING SALT INTO WATER SHUFFLING OF CARDS MIXING OF SAND AND IRON CUTTING OF HAIR

8. A change which cannot be reversed back are called irreversible changes .  

9. Examples 1 . Burning of matchstick 2. Burning of wood 3. Burning of paper 4. Passage of time 5. Broken cupboard 6. Breaking of glass 7. Extraction of petroleum 8. Changes in appearance Growth of plant Sharpening of pencil Spoilage of food Cutting of vegetables Baking of bread Changing milk into curd Rusting of iron

10. Stretching of rubber band Burning of paper. Washing of clothes. Breaking of glass Rusting of iron. IN WHICH OF THE FOLOWING CHANGES ARE NEW SUBSTANCES FORMED?

11. Physical changes Changes that involve only a change in physical properties of a substance, but where no new substance is formed, are called physical changes.

12. Reversible physical changes

13. Irreversible physical changes The physical changes that can’t be reversed . 1.Breaking of glass 2.Shredding of paper 3. Conversion of wood into sawdust 4.Grinding of wheat into flour

14. Characteristics of physical change A physical change effects only physical properties. The molecules of the substance involved do not change. No new substance is formed. Physical change can be reversible or irreversible. The amount of energy required to carry out a physical change is small compared to amount needed for chemical change.

15. Chemical change https://www.youtube.com/watch?v=PROpBsX5KiE

16. Changes that involve the formation of new substances are called chemical changes. https://www.youtube.com/watch?v=fyX81t2k66E

17. Reactants The substance that take part in a chemical reaction are called Reactants.

18. Products The substances that are formed as a result of the chemical reaction are called products.

19. A chemical reaction is represented as:

20. Burning of Paper paper Ash+ carbon dioxide +water.

21. Burning of Candle Melting of wax- physical change Burning of wax- chemical change- carbon dioxide+ soot + water(products)

22. What is the change that you see?

23. What is this? Why did this become like this? What type of change is it?

24. An iron nail left out in moist air rusts. Rusting is a chemical change in which iron reacts with oxygen and forms rust (iron oxide). Since a new substance is formed, rusting is a chemical change.

25. More examples of chemical change Cooking of food frying an egg digestion of food souring of milk mixing acid and base baking a cake sugar to caramel sugarcane to sugar Fireworks Jute to thread Lighting of matchstick

26. Vinegar + baking soda Carbon dioxide https://www.youtube.com/watch?v=LR5TNtznOfA&pp=qAMBugMGCgJhchAB

27. Charring of sugar Sugar charcoal+ water

28. Characteristics of chemical change 1. A chemical change is a result of chemical reaction between reactants to form one or more products. 2. New substances with different properties are formed. 3. Chemical changes are mostly irreversible in nature. 4. The amount of energy involved in a chemical change is substantial.

29. SLOW AND FAST CHANGE

30. FAST CHANGES Changes that take place instantaneously or over a short period of time are called fast changes. Eg ) heating of water, burning of crackers

31. Slow changes Changes that take place over a long period of time are called slow changes. Eg ) growing of seed to plant, rusting of iron.