MnSTEP Teaching Activity Collection > MnSTEP Activities > Bowling Balls: Will they Sink or Will they Float?

# Bowling Balls: Will they Sink or Will they Float?

#### Summary

Students will investigate what determines whether a material will sink or float. They will be given a bowling ball and have to make measurements and conclusions on whether their bowling ball will float, hover, or sink when placed in an aquarium.

## Learning Goals

This activity is designed for students to gain valuable skills in measurement, significant figures, and understanding the physical property of density. Students will present their conclusion to their peers and justify their decision based upon data collected and analyzed from their measurements.

Vocabulary Words: Density (most will "know" this, but this will be an application)
Significant Figures, Buoyancy

## Context for Use

This activity is designed for a 45-50 minute class period. This activity has been used successfully in both 9th grade physical science and chemistry. This is an excellent activity for the beginning of the year when students need to have a firm grasp on the importance of significant figures in all of their measurements and calculations. It can be used as intrinsic and extrinsic properties are introduced and discussed. It also fits in nicely as intrinsic and extrinsic properties are discussed and investigated.

Subject: Chemistry:General Chemistry:Properties of Matter, Physics:General Physics:Measurement/Units, Mathematical Physics
Resource Type: Activities:Lab Activity

## Description and Teaching Materials

Obtain at least 6 bowling balls from a local bowling alley: 6, 8, 10, 12, 14, 16lb balls. Call a local bowling alley and ask for any bowling balls that they would like to donate. Most alleys have plenty of bowling balls that they are willing to get rid of. Place all of these bowling balls on a lab table, using masking tape rolls to keep them in place. Ask students if bowling balls float in water. Build upon student ideas about what causes something to float or sink.

Students should be divided into as small of groups as possible to place more responsibility on each member. Group size is dependent on the number of bowling balls available to measure. Provide students with meter sticks, string, and a scale capable of measuring the weight or mass of the bowling balls. Give the students the challenge of determining whether their bowling ball will float or sink. Depending on teaching style, buoyant force and density can be discussed at this time or possibly later.

Students need to choose a bowling ball and then determine what the density of the ball is. Students should be encouraged to find the range of possible densities that the bowling ball could have, using the uncertainty of measurement in the ruler and scale. After students have reached their conclusion, have them place their data on the board in front. Have an aquarium filled with ¾ with water (place a piece of foam on the bottom of the aquarium). Call the lab groups up one at a time and let them explain whether their bowling ball will sink or float and how they can justify their conclusion.

## Teaching Notes and Tips

Density is independent of sample size, so when you ask students follow up questions about how their decision would change if you were to add another hole to the bowling ball, they will see that it doesn't matter how much of something you have that determines if it will float, it depends on what types of material you are comparing.

Bowling balls less than 12 lbs will float. Bowling balls greater than 12 lbs will sink. Bowling balls that are marked 12 lbs have a density very close to 1 g/mL and will sink, hover, or float. Give the 12 lb ball to the advanced group. Give the 6 and 16 pound balls to the groups who need the best chances of success.

Densities of other liquids can be found at: http://www.simetric.co.uk/si_liquids.htm

Areas of confusion for students include misconceptions about the terms density and weight.

## Assessment

Students can be evaluated on this activity using a chart of densities of different liquids. Have students determine in which liquids each of the bowling balls will float.

A test question that evaluates if students can apply the knowledge gained from this lab experience is:

Explain why an iron nail sinks when dropped in water but a ship made of iron can float.

II.A.2
II.E.1,2