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7 Science > Physical And Chemical Changes > Flashcards

Physical And Chemical Changes Flashcards

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1
Q

What do you understand by physical properties of a substance?

A

Properties such as shape, size, colour, and state of a substance is called its physical properties.

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2
Q

What is physical change?

A

A change in which substance undergoes a change in its physical properties is called physical change.

In such a change no new substance is formed.

A physical change is generally reversible.

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3
Q

What happens when you leave a piece of iron in open?

A

It acquires a film of brownish substance known as rust

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4
Q

What is the colour of the flame when you burn a ribbon of magnesium?

A

Brilliant white light.

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5
Q

Write chemical reaction representing burning of magnesium strip.

A

Mg + O2 -> MgO (Magnesium Oxide)

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6
Q

Write the equation representing mixing of magnesium ash with water.

A

MgO + H2O -> Mg(OH)2 Magnesium Hydroxide

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7
Q

Common name of Copper sulphate.

A

Blue vitriol

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8
Q

What will happen if you add a iron nail in a solution of copper sulphate , water and dilute sulphuric acid?

A

Blue colour of the solution will turn green due to formation of iron sulphate.
Brown colour copper will be deposited on the nail

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9
Q

what will happen when you pass carbon dioxide gas through lime water?

A

Calcium carbonate will be formed which will make the water look milky.

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10
Q

What happens when you add a pinch of baking soda into vinegar?

A

Hissing sound will come.
Bubbles of gas will be visible.
This gas will be carbon dioxide.

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11
Q

What is chemical composition of vinegar?

A

It contains acetic acid.

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12
Q

What is the chemical composition of baking soda?

A

It contains Sodium hydrogen Carbonate.

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13
Q

Define chemical change.

A

A change in which one or more new substances are formed is called a chemical change. It is also called chemical reaction.

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14
Q

What is the chemical composition of baking soda?

A

It contains Sodium hydrogen Carbonate.

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15
Q

Chemical change and chemical reactions are one and same thing. True or False?

A

True

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16
Q

What is the significance of chemical change in our life?

A

It is used to extract metals from its ore
Medicines are made through chain of chemical changes
Useful new materials like plastic and detergents are produced by chemical reactions

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17
Q

Chemical change and chemical reactions are one and same thing. Tue or False?

A

True

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18
Q

Apart from new products what are other things that may happen during a chemical change?

A
  1. Heat light or any other radiation ( ultraviolet for example) may be given off or absorbed.
  2. Sound may be produced
  3. A change in smell may take place or a new smell may be given off
  4. A colour change may take place
  5. A gas may be formed
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19
Q

Is explosion of firework a chemical reaction? Explain.

A

Yes.

Explosion produces heat, light, sound and gas

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20
Q

When food gets spoiled , it produces a foul smell. Is it a chemical change? Explain.

A

Yes it is a chemical change as the smell is changing. Composition of food particles also changes.

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21
Q

Slice of apple turns brown in colour. Is it chemical change? Explain.

A

Yes it is chemical change as the colour has changed

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22
Q

What is Ozone? What is the advantage of ozone?

A

Ozone is a layer in our atmosphere.
It absorbs Ultraviolet radiation of sun and breaks down into oxygen.
In absence of Ozone harmful radiation will reach earth and harm humans and other life forms.

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23
Q

Is photosynthesis chemical change? Explain.

A

Yes.
Light (radiation) and CO2 and other nutrients from soil are converted into food due to photosynthesis. Since new substance is produced it is chemical change.

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24
Q

Name two components that are essential for formation of rust on iron

A

Oxygen and Water (or water vapour)

25
Q

People living near the coast often complain about faster rusting of their iron article. Why?

A

Air near ocean is high content of moisture. Sea water contains many salts. High moisture content in the air and presence of salts in the moisture causes faster rusting of iron articles

26
Q

How do we prevent iron from rusting?

A

By applying a coat of paint or grease.
This coating has to be done on a regular basis.
Another way is to deposit a layer of metal like chromium or zinc on iron.

27
Q

People living near the coast often complain about faster rusting of their iron article. Why?

A

Air near ocean is high content of moisture. Sea water contains many salts. High moisture content in the air and presence of salts in the moisture causes faster rusting of iron articles

28
Q

A fraction of ships iron is required to be replaced every year. Why.?

A

Air near ocean is high content of moisture. Sea water contains many salts. High moisture content in the air and presence of salts in the moisture causes faster rusting of iron and hence a portion of ships iron is required to be replaced every year.

29
Q

what is galvanisation?Give examples.

A

The process of depositing zinc on iron is called galvanization. This prevents rusting.
Water pipes in homes are galvanised to prevent rusting.

30
Q

What is stainless steel?

A

Stainless steel is made by mixing iron with carbon and metals like chromium , nickel and manganese. It does not rust.

31
Q

What is crystallisation?

A

It is a process of obtaining large crystals of pure substance from their solution. It is physical change.

32
Q

Give example of crystallization.

A

Take a cupful of water in a beaker.
Add few drops of dilute sulphuric acid.
Heat the solution.
When it starts boiling add copper sulphate powder slowly stirring it.
Continue adding copper sulphate powder till no more powder can be dissolved.
Filter the solution.
Allow it to cool.
DO not disturb the solution when it is cooling.
Look at the solution after some time.
You will see crystals of copper sulphate.
If not wait for some more time.

33
Q

Dissolving sugar in water is …….. change

A

Physical

34
Q

Burning of coal is …….. change

A

Chemical

35
Q

Melting of wax is ……. change

A

Physical

36
Q

Beating aluminium to make aluminium foil is chemical change . True/False.

A

False

37
Q

What type of change is digestion of food?

A

Chemical

38
Q

Cutting of wood into pieces is a chemical change . True or False

A

False

39
Q

Formation of manure from leaves is a physical change. True or False

A

False

40
Q

Iron pipes coated with zinc do not rust easily. True / False

A

True

41
Q

Iron and rust are same substance. True or False

A

False

42
Q

Condensation of steam is not a chemical change. True or False

A

True

43
Q

When a candle burns , both chemical and physical changes take place. Give another example of a familiar process in which both the physical and chemical changes take place.

A

Cooking of food.
Raw vegetables gets cooked - chemical change
Water changes into steam - physical change

44
Q

Chemical name of baking soda is ….

A

Sodium Hydrogen Carbonate

45
Q

What is the name of gas that we use in Kitchen

A

LPG , Liquified petroleum Gas

46
Q

When LPG is stored in the cylinder in ……. form

A

Liquid

47
Q

When LPG comes out of cylinder is turns into gas. Is it chemical change of physical change?

A

Physical

48
Q

What type of change takes place when the LPG burns

A

Chemical

49
Q

Anaerobic bacteria digest animal waste and produce biogas (Change A) . The biogas is then burnt as fuel (Change B) THe following statement pertain to these changes. Choose the correct one.

i) Process A is a chemical change
ii) Process B is a chemical change
iii) Both process A and B are chemical change
iv) None of the process is chemical change

A

Both process A and B are chemical change

50
Q

What is the height of iron pillar near Qutub Minar?

A

7 metres

51
Q

What is the weight of iron pillar near Qutub Minar?

A

6000 kgs

52
Q

How old is the iron pillar near qutub Minar?

A

1600 years old.

53
Q

What is the significance of iron pillar near Qutub Minar

A

It has not rusted even though it is 1600 years old.

54
Q

If you put iron nail in boiled water with oil layer at top - will the nail rust? Give reason

A

No.
Boiled water has no oxygen.
Layer of oil will prevent oxygen from mixing with water
In absence of oxygen no rust will form.

55
Q

If you put iron nail in boiled water will it rust?

A

Yes

56
Q

If you put iron nail in simple tap water , will it rust?

A

Yes

57
Q

Describe two changes that are harmful?

A
  1. Rusting of iron
  2. Soil erosion
  3. Burning of fossil fuel
58
Q

Explain why cutting of wood into small pieces and burning them considered as two different types of change

A

Cutting of wood- physical change

Burning of wood - chemical change

59
Q

Write reaction demonstrating assing of Carbon Dioxide through Lime water

A

Co2 + Ca(OH)2 (Lime Water)–>CaCO3 (Calcium Carbonate) + H2O

7 Science (2 decks)

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