Question

If 125 grams of ice cools from -1.1 degrees Celsius to -5.7 degrees Celsius, how many Joules of heat were transferred from the ice?

What I know:
q(heat)=?
m(mass)=125g
Delta T(change in temp)= (not sure, this is where i get mixed up)
C(specific heat)=2.1J/gxdegreescelcius

Answer 1

`q=-"1400 J"`

The negative sign means that energy was lost.

Explanation:

Use the following equation.

`q=mcDeltat`,

where:

`q` is the energy gained or lost, `m` is the mass, `c` is the specific heat, and `Deltat` is the change in temperature. `Deltat=T_"final"-T_"initial"`

Known

`m="125 g"`

`c=("2.1J")/("g"*""^@"C")`

`T_"initial"=-1.1^@"C"`

`T_"final"=-5.7^@"C"`

`Deltat=-5.7^@"C"-(-1.1^@"C")=-4.6^@"C"`

Unknown

`q`

Solution

Plug in the known values and solve for `q`.

`q=(150color(red)cancel(color(black)("g")))xx(2.1"J")/(color(red)cancel(color(black)("g"))*""^@color(red)cancel(color(black)("C")))xx(-4.6^@color(red)cancel(color(black)("C")))=-"1400 J"` (rounded to two significant figures)

The negative sign in front of Joules means that energy was lost.