Physical and Chemical Changes Test

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Physical and Chemical Changes Test - 6

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Question 1
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Directions For Questions

Fill in the blanks with the given word box.
bubbles, reaction, gases, condensation, colour, reactants, reversed, word, element, compound, products, boiling.

...view full instructions

Physical changes like boiling do not make new materials and are easily reversed e.g. by cooling, which causes ________.

A
condensation

B
reactants

C
reaction

D
colour

Solution

Condensation: The change of a gas or vapor to a liquid, either by cooling or by being subjected to increased pressure. When water vapor cools in the atmosphere, for example, it condenses into tiny drops of water, which form clouds.
Question 2
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Rust forms on:

A
tin

B
copper

C
iron

D
lead

Solution

Rust is a reddish- or yellowish-brown flaking coating of hydrated iron oxide that is formed on iron or steel by oxidation in the presence of moisture.
Question 3
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Weight of crucible + weight of magnesium wire = X (before heating)
Weight of crucible + weight product magnesium oxide = Y (after heating)
Which of the following option is correct?

A
X = Y

B
X < Y

C
X > Y

D
Depends on element

Solution

Magnesium wire($$Mg$$) on heating in air gains weight due to the formation of magnesium oxide ($$MgO$$ ). It is shown by the following reaction.
$$2 Mg _{(s)} + O_{{2}{(g)}}$$ $$\longrightarrow 2MgO_{(s)}$$
So according to the law of conservation of mass, Mass of reactant = Mass of product.
So, $$ \text {Mass of magnessium wire + Mass of oxygen gas = Mass of magnesium oxide} $$
$$\therefore \text {X + Mass of}$$ $$O_2$$ $$= Y $$

The above equation indicates that the mass of X is less than that of Y. i.e. $$X < Y$$
Hence, option $$B$$ is correct.
Question 4
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The change which is permanent and can not be measured by just reversing the condition is known as:

A
physical change

B
chemical change

C
Both A and B

D
None of the above

Solution

A chemical change is a permanent change in the sense that it cannot be reversed by just reversing the conditions.
Question 5
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Which of the following is not a physical change?

A
Tearing a paper

B
Bending an iron rod

C
Freezing water into ice

D
Curdling of milk

Solution

The tearing of paper is a physical change because it remains the same. Tearing a paper is a physical change because when the paper is torn only the appearance of the paper is changed and no new substance is formed. And freezing water into ice does not change its chemical constituents. Only phase changes from solid to liquid.

Cheese is made when an enzyme called rennet is added to milk. The rennet causes a chemical reaction where the milk solids curdle, separating themselves from the whey, or liquid portion of the milk
Question 6
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An example of a chemical change is:

A
formation of clouds

B
glowing of an electric light

C
dropping sodium into water

D
dissolving of salt in water
Solution
Chemical changes involve chemical reactions and the creation of new products. Typically, a chemical change is irreversible.
Examples are:
1. Dropping sodium into water
2. combustion (burning) of wood
3. metabolism of food in the body
4. cooking an egg
5. digesting sugar with the amylase in saliva
6. baking a cake
7. electroplating a metal
8. explosion of fireworks
9. rotting bananas
10. grilling a hamburger
11. milk going sour
Question 7
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An example of chemical change is:

A
water condensing on the outside of your cold beverage

B
bending a wire

C
slicing bread

D
freezing water

E
burning a candle

Solution

The burning of the candle is permanent because once it is burnt it cannot be converted into the candle. A new product is also formed with a composition different from the candle. Hence it is a chemical change. Whereas the rest of the options represent the physical change.
Hence, the correct option is E.
Question 8
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Which salt is obtained from the evaporation of sea water?

A
Sodium chloride

B
Magnesium chloride

C
Calcium chloride

D
Potassium chloride

Solution

The concentration of salt in sea water is 35 parts per thousand i.e 3.5% of sea water's weight comes from dissolved salts.Thus, when the sea water evaporates, the salt that is left behind is sodium chloride.
Hence, the correct answer is option (A).
Question 9
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What is a chemical change?

A
Change in size, shape

B
Change from one substance to another new substance

C
Change in temperature of the substance

D
None of above
Question 10
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A man painted his main gate made up of iron, toi) Prevent it from rusting.ii) Protect it from sun.iii) Make it look beautiful.iv) Make it dust free.

A
$$(i)$$ $$and$$ $$(ii)$$

B
$$(ii)$$ $$and$$ $$(iii)$$

C
$$only$$ $$(ii)$$

D
$$(i)$$ $$and$$ $$(iii)$$

Solution

The correct answer are option (D).
To prevent iron from rusting and make it look beautiful, it is necessary to paint it.

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Physical and Chemical Changes Test - 6

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Physical and Chemical Changes Test - 6

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Question 1

condensation

reactants

reaction

colour

Solution

Question 2

tin

copper

iron

lead

Solution

Question 3

X = Y

X < Y

X > Y

Depends on element

Solution

Question 4

physical change

chemical change

Both A and B

None of the above

Solution

Question 5

Tearing a paper

Bending an iron rod

Freezing water into ice

Curdling of milk

Solution

Question 6

formation of clouds

glowing of an electric light

dropping sodium into water

dissolving of salt in water

Solution

Question 7

water condensing on the outside of your cold beverage

bending a wire

slicing bread

freezing water

burning a candle

Solution

Question 8

Sodium chloride

Magnesium chloride

Calcium chloride

Potassium chloride

Solution

Question 9

Change in size, shape

Change from one substance to another new substance

Change in temperature of the substance

None of above

Question 10

$$(i)$$ $$and$$ $$(ii)$$

$$(ii)$$ $$and$$ $$(iii)$$

$$only$$ $$(ii)$$

$$(i)$$ $$and$$ $$(iii)$$

Solution

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