Key ConceptsJust like solids, liquids additionally have their own characteristic thickness.The volume of a liquid can be measured straight with a graduated cylinder.The molecules of various liquids have actually various size and also mass.The mass and size of the molecules in a liquid and exactly how closely they are packed together determine the thickness of the liquid.Just like a solid, the thickness of a liquid amounts to the mass of the liquid split by its volume; D = m/v.The density of water is 1 gram per cubic centimeter.The density of a substance is the exact same regardless of the size of the sample.
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Students measure the volume and also mass of water to determine its density. Then they meacertain the mass of various quantities of water and also discover that the density is always the same. Students make a graph of the partnership between the volume and the mass of water.
Students will certainly be able to measure the volume and mass of water and calculate its thickness. Students will certainly be able to describe that since any volume of water constantly has actually the very same thickness, at a given temperature, that density is a characteristic residential or commercial property of water.
Downpack the student activity sheet, and also distribute one per student once mentioned in the task. The activity sheet will serve as the “Evaluate” component of each 5-E leskid arrangement.
Make certain you and your students wear properly fitting goggles.
Materials for Each GroupGraduated cylinder, 100 mlWaterBalance that steps in grams (able to meacertain over 100 g)Dropper
Materials for the DemonstrationWaterTwo similar buckets or huge containers
Do a demonstration to introduce the principle that water has actually thickness.
MaterialsWaterTwo identical buckets or big containers
Half-fill one bucket and also include only around 1 cup of water to the other.
ProcedureSelect a student to lift both buckets of water. Explore
Discuss through students just how to discover the volume and also mass of water.
Tell students that they are going to attempt to find the thickness of water.
Ask students:What 2 points carry out you must know in order to find the density of water?Students need to realize that they require both the volume and mass of a sample of water to uncover its thickness. How have the right to you measure a volume of water? Suggest that students use a graduated cylinder to meacertain volume in milliliters. Remind students that each milliliter equates to 1 cm3.
Have students find the mass of various volumes of water to show that the thickness of water does not depfinish on the size of the sample.
Inquiry to investigate
Do various amounts of water have actually the exact same density?
Materials for each groupGraduated cylinder, 100 mLWaterBalance that steps in grams (able to measure over 100 g)Dropper
ProcedureFind the mass of an empty graduated cylinder. Record the mass in grams in the chart on the activity sheet.
Pour 100 mL of water right into the graduated cylinder. Try to be as precise as possible by checking that the meniscus is right at the 100-mL note. Use a dropper to add or rerelocate small quantities of water.
Find the mass of 50 mL of water. Record the mass in the activity sheet. Calculate and record the density.
The thickness of water need to be close to 1 g/cm3. This is true for 100, 50, or 25 mL.
Ask students:Look at your values for thickness in your chart. Does the density of the different volumes of water seem to be about the same? Help students see that a lot of of the different worths for thickness are close to 1 g/cm3. They may wonder why their values are not all precisely 1 g/cm3. One reason might be inaccuracies in measuring. Anvarious other factor is that the thickness of water alters with temperature. Water is a lot of dense at 4 °C and at that temperature has actually a density of 1 g/cm3. At room temperature, roughly 20–25 °C, the density is about 0.99 g/cm3. What is the thickness of water in g/cm3? Students answers will certainly vary, yet their worths need to mostly be about 1 g/cm3.
Discuss student observations, information, and also graphs.
Ask students:Use your graph to find the mass of 40 mL of water. What is the density of this volume of water?The mass of 40 mL of water is 40 grams. Due to the fact that D = m/v and also mL = cm3, the density of water is 1 g/cm3.Choose a volume between 1 and 100 mL. Use your graph to find the mass. What is the thickness of this volume of water? Whether students weigh 100, 50, 25 mL or any various other amount, the thickness of water will certainly always be 1 g/cm3.
Tell students that density is a characteristic residential or commercial property of a substance. This indicates that the thickness of a substance is the same regardmuch less of the size of the sample.
Ask students:Is thickness a characteristic residential or commercial property of water? How execute you know?Density is a characteristic residential or commercial property of water bereason the thickness of any sample of water (at the very same temperature) is constantly the exact same. The thickness is 1 g/cm3.Extend
Have students consider whether the thickness of a huge item of a solid substance is the same as the thickness of a smaller sized piece.
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Give students time to calculate the thickness of each of the three samples drawn on their task sheet and answer the related concerns.
Ask students:The thickness of a liquid is the very same no matter what the size of the sample. Could this be true for solids, too? Calculate the thickness of each of the three samples to uncover out.Yes. The density of a solid substance is the very same no matter just how significant or small the sample. Sample A has actually a mass of 200 g. What is the density of Sample A? D = m/vD = 200g/100cm3D = 2 g/cm3If you cut Sample A in half and also looked at only one half, you would certainly have actually Sample B. What is the thickness of Sample B?If students execute not recognize what the mass is, tell them that it is fifty percent the mass of Sample A. Since Sample A was 200 g, Sample B is one half the volume and therefore one fifty percent the mass (100 g). D = m/vD = 100g/50 cm3D = 2 g/cm3If you cut Sample B in fifty percent you would certainly have Sample C. What is the density of Sample C? D = m/vD = 50g/25 cm3D = 2 g/cm3