Science Buddies: "Ask an Expert"

hi! im doing a project that i found here on science buddies its the burning calories one. can u please look at it and help tell how it relates to physics and chemistry i have to write a paragraph on each and what should i include in the background reserch??
thank you!:)
- hanna Yasin

Hi Hanna,

This is a great project. A good place to start researching how this project relates to physics and chemistry would be to research what are calories. Also since you'll be using the equation below you might want to research what the specific heat capacity of water is and what that number means/represents. Some google searches on these topics should get you headed in the right direction!

Qwater = mcΔT
where:

Qwater is the heat captured, in calories (cal);
m is the mass of the water, in grams (g);
c is the specific heat capacity of water, which is 1 cal/g°C (1 calorie per gram per degree Celsius); and
ΔT is the change in temperature (the final temperature of the water minus the initial temperature of the water), in degrees Celsius (°C).

Audrey

thanks audry! ok so i looked up what calories are but it doesnt really have the physics part in it. and what do u mean about the heat capacity of water?

The specific heat capacity of water is the amount of energy, in the form of heat, to cause the temperature of 1 gram of water to rise by 1 degree kelvin. Here is an example. Suppose you had an electric kettle that heats water using an electrical heating element. If that heating element provides 500 watts of power, then every second it would put 500 joules of energy into the water in the pot. If the pot held 1 liter of water, that would very close to 1000 grams of water. The specific heat capacity c_m for water is about 4.18 J/(gm K), so the temperature rise in the 1000 grams of water in 1 second would be

[ (500 J)/(1000 gm) ]/[ 4.18 J/(gm K) ] = 500/(1000*4.18) [J gm K]/[gm J] = 0.120 K

If we wanted to heat the water from 25 C to 100 C, that would be a rise of 75 K (1 degree C = 1 degree K), and it would take 75/0.120 = 627 seconds = 10.45 minutes. (If we don't watch it )

hi!!! ok im still working on this project and i need help on something! i dont know how to write a hypothesis and also.. i did a chart on the tem before and after the weight of food before and after ok then i need to use the formula what part should i put that in ?? should i put it in a chart or wheere? ans like the conclusion results observations im not sure.

Here's a good resource on writing your hypothesis: https://www.sciencebuddies.org/science- ... esis.shtml

I'm not sure I understand your second question about the chart. Can you explain some more?

Audrey

Hi, Hannayasin!

The link above should definitely do the trick for helping you to write a good hypothesis. As for the thermodynamics formula, Q = mc∆T, you should mention that in the introduction. When you present your results with the data from the experiment, your audience (if you are presenting this project in front of your class or at a fair) will already know about the formula and how you are going to use it. After you calculate the amount of heat captured by the calorimeter, you need to discuss your final values in your conclusion. Explain your results and possible sources of error. Be sure to be clear and concise!

Hope this helped,
RM