2. Tap water at 15 °C is used to fill an ice cube tray with...

2. Tap water at 15 °C is used to fill an ice cube tray with a total of 800 grams of water. How much heat must be removed from the water in the tray to produce ice cubes at 0 °C? 3. A farmer's rectangular pond measures 40 m by 80 m. In winter, a slab of ice (dice = 917 kg/m³) forms on the pond. If the mass of the ice slab is 1.76 x 10? kg, how thick is it? 4. A stack of college textbooks rests on a shelf in a closet. The total mass of the stack is 16 kg. If the bottom-most book on the stack measures 20 cm by 30 cm, how much pressure does the stack exert on the shelf?

Transcript

00:01 Hello students, in the first part of the question we have defined how much heat should be removed from water to produce ice cubes at zero degree celsius.

00:10 For that we can use equation q is equal to mc delta t where m is a mass, q is a heat energy in joules, c is a specific heat capacity and delta t is a change in temperature.

00:24 So delta t is given as zero degree celsius minus 50 degree celsius.

00:31 Therefore we can consider this as minus 50 degree celsius.

00:35 Now let us substitute all the values which is given in the question.

00:39 Then we get q is equal to mass which is 0 .8 kilogram into the specific heat capacity that is 4 .18 into minus 50 degree celsius and this is equal to heat q is equal to minus 50 .4 kilo joules.

00:57 So the negative sign here, the negative sign indicates that heat is being removed from the water to cool it down.

01:04 So 50 .4 kilo joules of heat must be removed.

01:19 Now coming to the second question we have to find the thickness of the ice slab.

01:24 We know the equation the density is equal to mass by volume or we can write density is equal to mass by density is equal to mass by volume can be written as area into thickness t.

01:45 So from this we can write the thickness t is equal to mass by density into area.

01:57 So now let us substitute all the given values.

01:59 The mass is given as 1 .76 into 10 raised to 5 kilograms divided by density that is 917 kilogram per meter cube into area which is 40 into 80 meters.

02:14 Calculating we get thickness t is equal to 0 .0611 meters...

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