Chapter 2

Heat and Temperature

Heat & TemperatureHEAT TEMPERATURE

Definition Flow of thermal energy

Average kinetic energy

Measuring Device Calorimeter Thermometer

Units Joules, calories °C, °F, K

•The omission of "degree" symbol for the Kelvin scale indicates that it is not relative to an arbitrary reference point such as the Celsius and Fahrenheit scales.

Measuring Devices

What Feels Cooler?

Accuracy refers to how close a measurement is to the true or correct

value for a quantity.

Precision refers to how close a set of measurements for a quantity are

to one another, regardless of whether or not the measurements

are correct.

Accuracy vs Precision

a

a

Larry, Curly and Moe are each given the same type of metal and are asked to measure its density. The actual density of the metal is 3.0 g/ml however they are not told this. They take four sets of measurements and use these to calculate the density of the metal for each set of measurements. Their results are given below.

Larry Curly Moe

2.5 g/ml 4.0 g/ml 4.0 g/ml

2.7 g/ml 2.0 g/ml 4.1 g/ml

3.1 g/ml 1.0 g/ml 4.1 g/ml

3.3 g/ml 5.0 g/ml 4.2 g/ml

1.Who is the most precise?2.Who is the most accurate?3.What is the percentage error (experimental error) of Larry’s reported density measurement?

See Notebook

For this example:

Larry, Curly and Moe are each given the same type of metal and are asked to measure its density. The actual density of the metal is 3.0 g/ml however they are not told this. They take four sets of measurements and use these to calculate the density of the metal for each set of measurements. Their results are given below.

Larry Curly Moe

2.5 g/ml 4.0 g/ml 4.0 g/ml

2.7 g/ml 2.0 g/ml 4.1 g/ml

3.1 g/ml 1.0 g/ml 4.1 g/ml

3.3 g/ml 5.0 g/ml 4.2 g/ml

1.Who is the most precise?Moe, he has the lowest range (0.2).

2. Who is the most accurate?Curly, his average is closest to 3.0 (the accepted value).

3. What is the percentage error (experimental error) of Larry’s reported density measurement?

Percentage Error

Percent error = your value - accepted value

accepted value 100%

Larry Curly Moe

2.5 g/ml 4.0 g/ml 4.0 g/ml

2.7 g/ml 2.0 g/ml 4.1 g/ml

3.1 g/ml 1.0 g/ml 4.1 g/ml

3.3 g/ml 5.0 g/ml 4.2 g/ml

Homework

• Worksheet Chapter 2 - 2