# Chemistry/Measuring Temperature

Science 8 Laboratory Investigation
MEASURING TEMPERATURE

Purpose

The purpose of this investigation is to learn to take temperature measurements with a thermometer and find how the temperature of a mixture is affected by the amounts of hot and cold water used to make the mixture.

Equipment Needed

2 – thermometers that read from –10oC to 110oC
3 – styrofoam cups
2 – 100 mL graduated cylinders

 Procedure: 1. (a) Partner #1: Pour exactly 100 mL of very cold water into a 100 mL graduated cylinder. Pour this cold water into a styrofoam cup. Partner #2: Pour exactly 100 mL of hot water into a 100 mL graduated cylinder. Pour this hot water into a second styrofoam cup. (b) Partner #1: Quickly measure and record the temperature of the cold water in its styrofoam cup. Partner #1: Quickly measure and record the temperature of the hot water in its styrofoam cup. (c) Quickly pour the cold water into the hot water cup, stir for a few seconds and then measure and record the temperature of the mixture. 2. (a) Partner #1: Pour exactly 50 mL of very cold water into a 100 mL graduated cylinder. Pour this cold water into a styrofoam cup. Partner #2: Pour exactly 100 mL of hot water into a 100 mL graduated cylinder. Pour this hot water into a second styrofoam cup. (b) Partner #1: Quickly measure and record the temperature of the cold water in its styrofoam cup. Partner #2: Quickly measure and record the temperature of the hot water in its styrofoam cup. (c) Quickly pour the cold water into the hot water cup, stir for a few seconds and then measure and record the temperature of the mixture. 3. (a) Partner #1: Pour exactly 100 mL of very cold water into a 100 mL graduated cylinder. Pour this cold water into a styrofoam cup. Partner #2: Pour exactly 50 mL of hot water into a 100 mL graduated cylinder. Pour this hot water into a second styrofoam cup. (b) Partner #1: Quickly measure and record the temperature of the cold water in its styrofoam cup. Partner #1: Quickly measure and record the temperature of the hot water in its styrofoam cup. (c) Quickly pour the cold water into the hot water cup, stir for a few seconds and then measure and record the temperature of the mixture.
Data Step Volume used Temperature
1 (b) 100 mL of cold water
100 mL of hot water
1 (c) 200 mL of mixture
2 (b) 50 mL of cold water
100 mL of hot water
2 (c) 150 mL of mixture
3 (b) 100 mL of cold water
50 mL of hot water
3 (c) 150 mL of mixture

Questions
1. This question uses the data for 100 mL of hot water and 100 mL of cold water.

(a) Calculate the starting temperature difference between the hot water and cold water, using the data for step 1 (b).

(b) How many degrees does the temperature rise when the hot water is added to the cold water (to create 200 mL of mixture)?

(c) Calculate the percentage of the mixture which is hot water as follows.

For example, if we use 25 mL of hot water and 100 mL of cold water, then:

Volume of hot water = 25 mL
Volume of mixture = 25 mL + 100 mL = 125 mL
Percentage of hot water = x 100% = 20%

OK, now calculate the percentage of hot water using YOUR data.

(d) Calculate the percentage temperature rise when hot water is added as follows.

Percentage temperature rise = x 100%

For example, if the cold water temperature is 15oC, the hot water temperature is 75oC and the mixture temperature is 35oC, then:

Starting temperature difference = 75oC – 15oC = 60oC
Temperature rise = 35oC – 15oC = 20oC
Percentage temperature rise = x 100% = 33%

OK, now calculate the percentage temperature rise using YOUR data.

2. Repeat all the calculations for question 1, using the data for 100 mL of hot water and 50 mL of cold water.

3. Repeat all the calculations for question 1, using the data for 50 mL of hot water and 100 mL of cold water.

4. Copy the results of your calculations for questions 1, 2 and 3 into the following table.

Mixture Percentage hot water Percentage temperature rise
100 mL hot + 100 mL cold
100 mL hot + 50 mL cold
50 mL hot + 100 mL cold

5. Lets make sure we know what the entries in the table mean.

• “Percentage of hot water” tells us what percentage of a mixture is made up of hot water.
• “Percentage temperature rise” tells us what the temperature rise is, as a percentage of the starting temperature difference.

Write a sentence or statement that describes any similarities you observe in the table for question 4.

6. If you mix 500 mL of cold water with 700 mL of hot water, will you expect the temperature of the mixture to be closer to the starting temperature of the cold water or closer to the starting temperature of the hot water?

7. BONUS QUESTION: If you mix 120 mL of water at 90oC with 30 mL of water at 15oC, what is the final temperature of the mixture?