A cup of water at 5°C (system) is placed in a microwave oven and the oven is turned on for one minute during which the water begins to boil. Which of the following option is true? [2026]

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Q.
A cup of water at 5°C (system) is placed in a microwave oven and the oven is turned on for one minute during which the water begins to boil. Which of the following option is true [2026]

1 $q = + ve, w = - ve, Δ U = - ve$

2 $q = + ve, w = - ve, Δ U = + ve$

3 $q = - ve, w = - ve, Δ U = - ve$

4 $q = + ve, w = 0, Δ U = - ve$

Ans.
(2)

$\underset{5 ° C}{H_{2} O (ℓ)} \to \underset{100 ° C}{H_{2} O (ℓ)} ⇄ \underset{100 ° C}{H_{2} O (g)}$

due to expansion

$w = - v e$

as heat is given to system so $q = + ve$ and internal energy of gas will be more than internal energy of liquid so $Δ U = + v e$

Solution

Q.
A cup of water at 5°C (system) is placed in a microwave oven and the oven is turned on for one minute during which the water begins to boil. Which of the following option is true [2026]

1 $q = + ve, w = - ve, Δ U = - ve$

2 $q = + ve, w = - ve, Δ U = + ve$

3 $q = - ve, w = - ve, Δ U = - ve$

4 $q = + ve, w = 0, Δ U = - ve$

Ans.
(2)

$\underset{5 ° C}{H_{2} O (ℓ)} \to \underset{100 ° C}{H_{2} O (ℓ)} ⇄ \underset{100 ° C}{H_{2} O (g)}$

due to expansion

$w = - v e$

as heat is given to system so $q = + ve$ and internal energy of gas will be more than internal energy of liquid so $Δ U = + v e$

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Solution

Q. A cup of water at 5°C (system) is placed in a microwave oven and the oven is turned on for one minute during which the water begins to boil. Which of the following option is true [2026]

1 q=+ve, w=-ve, ΔU=-ve

2 q=+ve, w=-ve, ΔU=+ve

3 q=-ve, w=-ve, ΔU=-ve

4 q=+ve, w=0, ΔU=-ve

Ans. (2) H2O(ℓ)5°C→H2O(ℓ)100°C⇄H2O(g)100°C due to expansion w=-ve as heat is given to system so q=+ve and internal energy of gas will be more than internal energy of liquid so ΔU=+ve

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Q.
A cup of water at 5°C (system) is placed in a microwave oven and the oven is turned on for one minute during which the water begins to boil. Which of the following option is true [2026]

1 $q = + ve, w = - ve, Δ U = - ve$

2 $q = + ve, w = - ve, Δ U = + ve$

3 $q = - ve, w = - ve, Δ U = - ve$

4 $q = + ve, w = 0, Δ U = - ve$

Ans.
(2)

$\underset{5 ° C}{H_{2} O (ℓ)} \to \underset{100 ° C}{H_{2} O (ℓ)} ⇄ \underset{100 ° C}{H_{2} O (g)}$

due to expansion

$w = - v e$

as heat is given to system so $q = + ve$ and internal energy of gas will be more than internal energy of liquid so $Δ U = + v e$