Key Concepts

Since thickness is a characteristic building of a substance, every liquid has its very own characteristic density.The density of a fluid determines even if it is it will float ~ above or sink in an additional liquid. A liquid will certainly float if it is less thick than the liquid it is inserted in.A liquid will sink if it is an ext dense 보다 the fluid it is placed in.

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Summary

Students will observe three household liquids stacked on each other and conclude the their densities should be different. They will certainly predict the loved one densities the the liquids and also then measure your volume and mass to check out if their calculations match their observations and also predictions.

Objective

Students will have the ability to determine even if it is a liquid will sink or rise in water by to compare its density to the thickness of water.

Evaluation

Download the student activity sheet, and distribute one per student when specified in the activity. The activity sheet will certainly serve as the “Evaluate” ingredient of every 5-E great plan.

Safety

Make sure you and your college student wear correctly fitting goggles. As soon as using isopropil alcohol, read and also follow all warnings ~ above the label. Isopropyl alcohol is flammable. Store it away from any type of flames or spark sources.

Materials for Each Group

BalanceIsopropyl alcohol, 70% or higherWaterGraduated cylinder2 similar tall clean plastic cups2 tea irradiate candles

Materials because that the Demonstration

BalanceIsopropyl alcohol, 70% or higherWaterGraduated cylinder2 the same tall clean plastic cups2 tea irradiate candles

Notes about the Materials

Isopropyl alcohol

The demonstrations and task work best with 91% isopropyl alcohol solution, i beg your pardon is easily accessible in plenty of grocery stores and pharmacies. If girlfriend can’t find 91% solution, 70% will certainly work, but your candle might not sink in it. If the happens, carry out not do that demonstration. Return the isopropil alcohol solution is 91% alcohol and 9% water, you deserve to disregard the little amount of water because that the objective of this lesson.

Balance

A an easy balance is all that is compelled for the second demonstration. Among the the very least expensive is Delta education Primary Balance (21-inch) Product #WW020-0452 (21-inch). Students can use the smaller sized version the the exact same balance, Delta Education, primary Balance (12-inch), Product #WW020-0452.


Engage

Do two demonstrations to present that different liquids have different densities.

Materials

BalanceIsopropyl alcohol, 70% or higher WaterGraduated cylinder2 the same tall clear plastic cups2 tea light candles

Teacher preparation

Use a graduated cylinder to measure 50 mL that water and pour it right into a clean plastic cup. Measure up 50 mL of isopropyl alcohol and also pour the into one more identical clean plastic cup.

Procedure

Demonstrate the thickness of 2 liquids through sinking and floatingPlace a tea irradiate candle in a cup with water and also another tea irradiate candle in a cup with alcohol. Host up the 2 cups.

Expected results

The candle will float ~ above water and also sink in alcohol.

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Ask students:

What could be causing one candle come float and the various other to sink? describe that the 2 candles room the same. Students should reason that the liquids should be different and also have different densities. Describe that the cup v the floating candle has water and the cup with the sinking candle consists of isopropyl alcohol.Do you think these 2 liquids have the very same or various densities?Students should conclude the the liquids should have various densities. They may even realize that water is more dense and also alcohol is less dense than the wax candle.

Procedure

Demonstrate the density of 2 liquids by to compare the mass of same volumes.Remove the candles from each liquid and tell students the each cup consists of the very same volume of liquid.

Carefully place the cups of water and alcohol top top opposite end of a balance.

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Expected results

The water will weigh more than the alcohol.

Ask students:

Which liquid is an ext dense?Students must agree that the water is much more dense 보다 the alcohol.How carry out you know? because the water has an ext mass than an equal volume of alcohol, water must be more dense. Explore

Demonstrate the liquids deserve to float or sink in various other liquids by making a thickness column through water, oil, and alcohol.

Materials because that the demonstration

Graduated cylinderWaterVegetable oilIsopropyl alcohol, 70% or higher

Note: If you would like the liquids to be an ext visible, include 1 autumn of food coloring come the water and another fall of a different color to the alcohol.

Procedure

Pour about 15 mL of water into the graduated cylinder. Gradually add about 15 mL the oil. Then gradually pour about 15 mL that alcohol on top. The liquids should type layers in the i graduated cylinder.

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Calculate the density of water, alcohol, and also oil.

Question come investigate

Why walk water sink in oil and also alcohol rise in oil?

Materials because that each group

WaterVegetable oilIsopropyl alcohol (70% or higher)Graduated cylinderBalance that steps in grams

This activity is composed for student to make actual dimensions of the mass and volume and to calculation the density of every liquid. Emphasize to students that they must be certain to accurately measure up the volume and mass of every liquid.

Procedure

Find the fixed of an empty i graduated cylinder. Document the mass in grams in the chart on the activity sheet.Pour 20 mL the water right into the i graduated cylinder. Try to be as specific as feasible by checking the the meniscus is best at the 20 mL mark. Weigh the graduated cylinder through the water in it. Record the massive in grams. Uncover the mass of only the water by subtracting the mass of the empty i graduated cylinder. Record the fixed of 20 mL of water in the chart. Use the mass and also volume of the water to calculation density. Record the thickness in g/cm3 in the chart.Follow measures 2–5 for alcohol and also then oil. Be sure to measure up the oil last since it does no rinse conveniently from the graduated cylinder. Table 1. Volume, mass, and also density because that water, alcohol, and oil WaterAlcoholOilMass of graduated cylinder + fluid (g)Mass that empty i graduated cylinder (g)Mass of fluid (g)Density of liquid (g/cm3)

Discuss whether the calculated densities assistance the bespeak the liquids class in the graduated cylinder.

Ask students:

Do the densities girlfriend calculated define why liquids float and also sink in one another? Explain.Yes, the water is the most dense and sinks in the oil. The alcohol is the the very least dense and floats ~ above the oil.Extend

As a demonstration, change the density of water so the a sinking carrot part floats.

You may pick to execute the adhering to either together a demonstrate or as an activity that students have the right to do.

Materials

Tall clean plastic cupWaterCarrot slice around ¼ inch thickSaltSpoon

Procedure

Pour water into a clear high plastic cup till it is about ½-filled. Location a part of carrot in the water.

Ask students:

Is the carrot much more or less dense than the water?Since the carrot sinks, students should conclude that the carrot is more dense than water.

Add around 1 teaspoon of salt to the water and also stir. Proceed to stir till the carrot floats come the surface of the salt water. If the carrot does no float to the surface, add more salt and stir.

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Expected results

The part of carrot need to float in the saltwater.

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Ask student:

Is it more or less thick than saltwater? due to the fact that the carrot floats in saltwater, students have to conclude that the carrot is less dense than saltwater.How does including salt adjust the thickness of the water?Dissolving salt in water boosts both the mass and volume the the water, however it boosts the mass more. Since D = m/v, increasing the mass an ext than the volume outcomes in boost in density.What would you mean if you put equal volumes of water and saltwater on opposite ends of a balance?If equal quantities of water and saltwater were placed on a balance, the saltwater would certainly be heavier.