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Cerrena [4.2K]
3 years ago
15

Which two observations below can be evidence that a chemical change has occurred

Chemistry
1 answer:
larisa86 [58]3 years ago
5 0
Vaporization and Production of bubbles. Production of heat and melting are physical changes
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Be sure to answer all parts. A person drinks four glasses of cold water (3.2 degree C) every day. The volume of each glass is 2.
Lelechka [254]

Explanation:

(a). The given data is as follows.

Volume of one glass of water = 2.2 \times 10^{2} ml = 220 ml

Volume of 4 glass of water = 220 \times 4 = 880 ml

We known that density of water is 1 g/ml.  Therefore, calculate the mass of water as follows.

       Mass of water = 880 ml \times 1 g/ml

                               = 880 gm

                               = 0.88 Kg               (as 1 kg = 1000 g)

The relation between heat energy, mass and temperature change is as follows.

            Q = mC \Delta T

\Delta T = (37 - 3.2)^{o}C = 33.8^{o}C

Putting the given values into the above formula as follows.

         Q = mC \Delta T

             = 0.88 \times 4.186 J/g^{o}C \times 33.8^{o}C

             = 124.5 kJ

Hence, the body have to supply 124.5 kJ to raise the temperature of the water to 37 degree C.

(b).      As we know that the heat of fusion of ice is 333 J/g.

So, energy required for 8.4 \times 10^{2} g or 840 g is as follows.

          333 \times 840 = 279.72 kJ

Heat capacity of water= 4.184 J/g^{o}C

Now, heat energy will be as follows.

           Q = 4.184 \times 840 g \times 37^{o}C

               = 130.03 kJ

Therefore, total heat required = (279.72 + 130.03) kJ

                                                  = 409.75 kJ

Hence, for the given situation your body should lose 409.75 kJ  of heat.

6 0
4 years ago
What would you need to do to calculate the molality of 10 g of NaCl in 2 kg of
jasenka [17]

Answer:

O B. Convert the 10 g of NaCl to moles of NaCl.

Explanation:

The formula for finding the molality is m=moles of solute/kg of solvent. The solute for this question is NaCl and the solvent is water.

(10g NaCl)(1 mol NaCl/58.44g NaCl)=0.1711 mol NaCl

58.44 is the molar mass of NaCl

m=0.1711 mol NaCl/2 kg H2O

m=0.085557837

7 0
3 years ago
7.71 Classify each of the following as exothermic or endothermic:
timama [110]

A. Heat is released, so the reaction is <u>exothermic</u>.

B. Heat is absorbed, so the reaction is <u>endothermic</u>.

C. Heat is released, so the reaction is <u>exothermic</u>.

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2 years ago
If Thomson’s atomic theory was accurate, what would the results of Rutherford’s gold foil experiment have been?
Arisa [49]

Answer:

If Thomson's atomic theory was accurate, the positively charged particles would have gone through the foil.

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2 years ago
Pick a key concept that you understand well and explain it in a way that an elementary school student could understand.
Gwar [14]
Colors!!
We know about all the colors in the rain bow but do you know how most of them are made?

Red and blue and yellow can make sooooo many different colors if you mix them together.

For example red + blue = purple! This is because red, blue and yellow are primary colors and these colors are colors that can make up other colors.
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