Assessment Items

Malcolm and Dave have two different ideas about how to determine the melting point of butter.

Malcolm designs an experiment to try to find the melting point of butter using five different hot plates. Malcolm puts a stick of butter with a thermometer in the butter in a beaker on each of the five hot plates. Each hot plate is set to a different temperature: “Low”, “Low-Medium”, “Medium”, “Medium-High”, and “High.” After 10 minutes Malcolm checks the state of the butter and the temperature of the butter.

Here is Malcolm’s data table:

1. Based on Malcolm’s data table, what do you think is the melting point of butter?

A. Between 25°C and 30°C

B. Between 30°C and 35°C

C. Between 35°C and 40°C

D. Between 40°C and 45°C

2. What data from Malcolm’s data table justifies your answer?

A. The butter was a solid at 35°C and was a liquid at 40°C

B. Sometimes butter is solid and sometimes it is a liquid

C. When you turn up the hot plate, the butter melts faster

D. It takes at least 10 minutes for the butter to melt

Dave now decides he wants to try his own experiment.

Dave places one stick of butter in a beaker and places the beaker on a hotplate set to “Medium-High.” He places a thermometer in the butter and checks the temperature every minute.

Here is Dave’s data table:

3. Based on Dave’s data table, what do you think is the melting point of butter?

A. Between 28°C and 31°C

B. Between 31°C and 34°C

C. Between 34°C and 37°C

D. Between 37°C and 40°C

4. Which evidence best justifies your choice?

A.The butter was a solid between 31°C and 34°C

B. When you turn up the hot plate, the butter melts

C. The butter was a solid at 34°C and had melted to a liquid at 37°C

D. The butter was a liquid between 37°C and 40°C

4.1 What reasoning best supports your claim and evidence? Choose only one.

A. Melting has happened when the butter is a liquid.

B. The melting of butter occurs at a specific temperature.

C. The heat from the hot plate causes molecules in the butter to move faster.

D. Butter melts between the highest temperature at which it was a solid and the lowest temperature at which it was a liquid.

5. Which experiment do you think will give a better estimate for the melting point of butter?

A. Malcolm's experiment

B. Dave's experiment

C. Malcolm and Dave's experiments give equally good estimates

D. There is no way to determine

6. Which of the following reasons best supports your choice above?

A. Malcolm measured all of the hot plates after the same amount of time heating.

B. Dave’s temperature measurements were closer together.

C. Both Malcolm and Dave measured the temperature of butter as a solid and as a liquid.

D. There is not enough information given.