Mass, Volume and Dissolving Lesson 14 Mass, Volume and Dissolving

Lesson 14 – Mass, Volume, and Dissolving You will use equal volumes of water and alcohol (you will mass each one separately) and will predict what will happen to the mass and volume after mixing the two substances. You will also conduct an investigation to determine what happens to the mass of salt when it is dissolved in water. 2

Lesson 14 - COS 1.0 1.1 1.2 1.3 1.4 1.5 4.0 3

Objectives Predict what happens to the mass and volume of a solute and a solvent when these substances are mixed together to form a solution. Perform an inquiry to test your predictions. Design and conduct an inquiry to investigate whether a change in mass occurs when sodium chloride dissolves in water.

Getting Started In your notebook, answer the following: Why is mass, and not volume, used to measure the amount of matter in an object? . Go over the proper procedure to pour an exact volume of water into a graduated cylinder.

Mass: The amount of matter in an object Lesson 14 Solubility: The amount of solute that will dissolve in a solvent at a given temperature and pressure Mass: The amount of matter in an object Volume: The amount of space occupied by a sample of matter Solid: A phase or state of matter in which a substance has a definite shape and volume 6

Lesson 14.1 – Question Is the volume and mass of a solution different from the combined volume and combined mass of the two separate substances that make up the solution? 7

Lesson 14.1 If….. then…. because… Hypothesis 8

SAFETY Wear your safety goggles throughout both inquiries. If you spill the ethyl alcohol, immediately tell your teacher.

Lesson 14.1 - Procedure Gather materials. Construct a data table. Pour 50 mL of water (colored) into a graduated cylinder. Pour 50 mL of ethyl alcohol into another graduated cylinder. Mass & record each cylinder and contents. Predict what the volume and mass will be after you mix the water and ethyl alcohol. Pour the ethyl alcohol into the graduated cylinder with water. Record volume. Mass both graduated cylinders and the combined liquids. Record mass. 10

Mass of liquids and cylinders Predicted measurements Results 14.1 Mixing Water and Alcohol Liquid Volume of liquids (mL) Mass of liquids and cylinders Water 50.0 Alcohol Predicted measurements (water and alcohol) Actual measurements Differences 11

Lesson 14.1 – Conclusion Water has space between the molecules that allows soluble substances to occupy that space. The combined volume of a separate solvent and a solute is greater than that of the solution they form. Mass, not volume, is conserved during dissolving. 12

Lesson 14.2 – Question What happens to the mass and volume of one type of matter when it is dissolved in another type of matter? 13

Lesson 14.2 If….. then…. because… Hypothesis 14

Lesson 14.2 - Procedure Dry the beaker and place it on the table. Put a small quantity (about two lab scoops) of salt into a test tube. Stand the test tube in the beaker. Pour water in a second test tube to a depth of 4 cm. Ensure that the outside of the tube is dry. Stand this in the beaker. Measure the mass of the tubes and beakers on the balance. Pour the water carefully into the salt. Gently shake the tube side to side until the salt is dissolved. Do not put your finger over the end of the test tube. Measure the mass of the two tubes, the solution, and the beaker. Calculate any changes in mass. 15

Results 14.2 Dissolving a Solid & Measuring Mass Initial mass of test tubes, beaker, salt and water (g) Final mass of test tubes, beaker, and dissolved salt solution (g) Difference/ change in mass (g) 16

Lesson 14.2 – Conclusion Water has space between the molecules that allows soluble substances to occupy that space. The combined volume of a separate solvent and a solute is greater than that of the solution they form. Mass, not volume, is conserved during dissolving…………. 17