Unit A Lesson A4 Solubility and Concentration
Completion requirements
Lesson A4: Solubility and Concentration
Video Lesson
Why are some solutions stronger than others? How do we measure the strength of solutions? Watch the video below to learn more about solutions and concentration.
Lesson A4: Solubility and Concentration
Figure A.2.4.1 – The Uyuni Salt Flats are located in Bolivia.
Figure A.2.4.2 – A salt flat is the remains of a dried-up lake.
Figure A.2.4.3 – The Great Salt Lake in Utah has a high concentration of salt.
Reading and Materials for This
Lesson
Science in Action 8
Reading: Pages 24–28
Materials:
2 tall cups, baking soda, warm water, string (kitchen twine or wool), scissors, spoon, small plate.
The Flat and the Fast
Some deserts around the world contain large flat landscapes covered with salt. These salt flats are the remains of ancient lakes. Salt flats require two conditions to form. Water cannot drain away through the underlying rock of the lake. Also, the lake needs to be in a dry area where it is not refilled by rain or snow. When these conditions are in place, the only way water can leave the lake is through evaporation to the atmosphere. Minerals, or salts, dissolved in the lakewater are left behind as the salt flat.
The Uyuni Salt Flat in Bolivia (Figure A.2.4.1) is the largest salt flat in the world. It covers an area of 10 000 square kilometers, which is about 12 times larger than the size of Calgary. The Bonneville Salt Flats in Utah, USA, were once covered by a huge lake. The nearby Great Salt Lake (Figure A.2.4.3) still contains water from that ancient lake. People race cars up to 600 km/h on the Bonneville Salt Flats. They can reach high speeds because the surface is so flat!
Some deserts around the world contain large flat landscapes covered with salt. These salt flats are the remains of ancient lakes. Salt flats require two conditions to form. Water cannot drain away through the underlying rock of the lake. Also, the lake needs to be in a dry area where it is not refilled by rain or snow. When these conditions are in place, the only way water can leave the lake is through evaporation to the atmosphere. Minerals, or salts, dissolved in the lakewater are left behind as the salt flat.
The Uyuni Salt Flat in Bolivia (Figure A.2.4.1) is the largest salt flat in the world. It covers an area of 10 000 square kilometers, which is about 12 times larger than the size of Calgary. The Bonneville Salt Flats in Utah, USA, were once covered by a huge lake. The nearby Great Salt Lake (Figure A.2.4.3) still contains water from that ancient lake. People race cars up to 600 km/h on the Bonneville Salt Flats. They can reach high speeds because the surface is so flat!
Watch More
Salt Flats
Watch this video to see some beautiful time-lapse photography of the Uyuni Salt Flats. Salt crystals are very shiny. This property of salt makes salt flats appear to reflect the sky.
Watch this video to see some beautiful time-lapse photography of the Uyuni Salt Flats. Salt crystals are very shiny. This property of salt makes salt flats appear to reflect the sky.
Figure A.2.4.4 – Caves contain interesting limestone formations.
Figure A.2.4.5 – Stalactites hang from cave ceilings.
Figure A.2.4.6 – Stalagmites grow from cave floors.
Cave Precipitation
We often use the word “precipitation” to describe water, such as snow or rain, falling from the sky. In science, there is another way to define the word “precipitation”. Precipitation occurs when a solid forms from a solution. The solid is called a precipitate. One way that precipitates can form is when solvent evaporates from a solution. Salt flats are an example of precipitation.
Another natural example of precipitation occurs in underground limestone caves . The rock layers above the cave contain a mineral called calcite. When surface water drains downward through soil and rock, it dissolves calcite. This solution of calcite in water eventually reaches the cave ceiling, where drops of the solution fall to the cave floor. On the ceiling, tiny solid particles of calcite are left behind when the solution drips to the floor. Over time, the particles of precipitated calcite grow into icicle-like formations called stalactites. On the cave floor, water from the drops of calcite solution evaporates. This also leaves behind a precipitate, which slowly grows upward to form stalagmites.
We often use the word “precipitation” to describe water, such as snow or rain, falling from the sky. In science, there is another way to define the word “precipitation”. Precipitation occurs when a solid forms from a solution. The solid is called a precipitate. One way that precipitates can form is when solvent evaporates from a solution. Salt flats are an example of precipitation.
Another natural example of precipitation occurs in underground limestone caves . The rock layers above the cave contain a mineral called calcite. When surface water drains downward through soil and rock, it dissolves calcite. This solution of calcite in water eventually reaches the cave ceiling, where drops of the solution fall to the cave floor. On the ceiling, tiny solid particles of calcite are left behind when the solution drips to the floor. Over time, the particles of precipitated calcite grow into icicle-like formations called stalactites. On the cave floor, water from the drops of calcite solution evaporates. This also leaves behind a precipitate, which slowly grows upward to form stalagmites.
Try It!
Growing Stalactites
Try this experiment to precipitate stalactites from a saturated solution of baking soda in water.
Materials:
Try this experiment to precipitate stalactites from a saturated solution of baking soda in water.
Materials:
- 2 tall cups
- Baking soda
- Warm water
- String (kitchen twine or wool)
- Scissors
- Spoon
- Small plate
Instructions:
- Fill both cups with warm water.
- Place a cup on either side of the small plate.
- Add 7 spoonfuls of baking soda to each cup and stir.
- Cut one piece of string long enough to connect both cups of water. The string ends should touch the bottom of each cup, and the string should slightly sag between the two cups.
- Soak the string in one cup of baking soda solution.
- Connect both cups with the soaked string. The string should slightly sag between the two cups, over the plate.
- Let the cups, plate, and string sit in a warm place for five days.
- After five days, observe the string.
- Watch this video to see the results of this experiment.
Questions:
Think about the following questions very carefully. Then, type or write your answers. After you have your answers, click the questions for feedback.
Think about the following questions very carefully. Then, type or write your answers. After you have your answers, click the questions for feedback.
Baking soda solution travelled up the string from the cups. When solution reached the saggy part of the string, water dripped down from the string onto the plate. This left a precipitate of solid baking soda on the string, forming “stalactites”.
Baking soda solution dripped from the string onto the plate. When the water solvent evaporated from the baking soda solution on the plate, it left behind a precipitate of solid baking soda, which formed “stalagmites”.
Watch More
Amazing Caves
Watch this video to see some spectacular cave formations.
Watch this video to see some spectacular cave formations.
Precipitation of solids
This video shows two precipitation experiments using a supersaturated solution of sodium acetate. Supersaturated solutions dissolve more than the maximum amount of solute, but the smallest bit of disturbance to the solution can cause the solute to precipitate.
This video shows two precipitation experiments using a supersaturated solution of sodium acetate. Supersaturated solutions dissolve more than the maximum amount of solute, but the smallest bit of disturbance to the solution can cause the solute to precipitate.
Connections
Figure A.2.4.7 – Medication must be measured carefully to provide the correct concentration to the body.
Figure A.2.4.8 – People take different amounts of medication depending on their body weight.
Connections – Health and Wellness
>> Medical Concentrations
Measuring concentration is important in the medical field. For example, measuring concentration is important when giving patients medicine. The correct dose of medication often depends on the size of the person. A baby needs a much smaller amount of medication compared to an adult, to have a similar concentration in the body. Medication concentrations are usually measured in milligrams per kilogram of body weight (mg/kg).
Saline solutions of salt and water are frequently used for medical purposes. Saline is used to clean wounds and is found in eye drops. It flows in intravenous (IV) lines for sick people who need to get more fluids into their bodies. Salt is measured carefully when making saline so that the solution has a similar concentration to body fluids. The concentration of saline that is used most often is 9 grams per litre (g/L).
The concentration of substances in blood or in urine help diagnose medical problems. For example, the colour of urine is related to its concentration. Normal, healthy urine is pale in colour. If a person has dark urine, they are dehydrated and need to get more fluids into their body. Dehydration can be caused by excessive sweating, vomiting, or diarrhea. Dehydration can cause death if water in the body is not replenished.
>> Medical Concentrations
Measuring concentration is important in the medical field. For example, measuring concentration is important when giving patients medicine. The correct dose of medication often depends on the size of the person. A baby needs a much smaller amount of medication compared to an adult, to have a similar concentration in the body. Medication concentrations are usually measured in milligrams per kilogram of body weight (mg/kg).
Saline solutions of salt and water are frequently used for medical purposes. Saline is used to clean wounds and is found in eye drops. It flows in intravenous (IV) lines for sick people who need to get more fluids into their bodies. Salt is measured carefully when making saline so that the solution has a similar concentration to body fluids. The concentration of saline that is used most often is 9 grams per litre (g/L).
The concentration of substances in blood or in urine help diagnose medical problems. For example, the colour of urine is related to its concentration. Normal, healthy urine is pale in colour. If a person has dark urine, they are dehydrated and need to get more fluids into their body. Dehydration can be caused by excessive sweating, vomiting, or diarrhea. Dehydration can cause death if water in the body is not replenished.
Figure A.2.4.9 – Saline, or salt solution, is created with specific concentrations for different purposes.
Figure A.2.4.10 – The concentration of urine can indicate health problems.
Connections
Figure A.2.4.11 – Pharmacists prepare medicines for patients.
Figure A.2.4.12 – A prescription tells a pharmacist the correct amount of medicine to give a patient.
Connections – Career
>> Pharmacist
Pharmacists work at hospitals and drugstores. They are responsible for measuring and giving the correct dose of medicines to patients. Pharmacists also need to know the side effects of different medicines, and how they interact with each other.
>> Pharmacist
Pharmacists work at hospitals and drugstores. They are responsible for measuring and giving the correct dose of medicines to patients. Pharmacists also need to know the side effects of different medicines, and how they interact with each other.
Watch More
Becoming a Pharmacist
Watch this video to learn more about pharmacy careers.
Watch this video to learn more about pharmacy careers.
Think • Interpret • Decide
Making Solutions
Why do different solutions have different concentrations? What factors affect the concentration of a solution?
Try this interactive activity on solutions from PHET Interactive Solutions. Make sure the concentration measuring probe is dragged into the solution to get a numerical reading.
Play with the different buttons for adding solute, adding water, and evaporation. Observe what happens to the concentration reading when you:
Try this interactive activity on solutions from PHET Interactive Solutions. Make sure the concentration measuring probe is dragged into the solution to get a numerical reading.
Play with the different buttons for adding solute, adding water, and evaporation. Observe what happens to the concentration reading when you:
- Add solute, but don’t add more water
- Add solute, and then add more water
- Evaporate water from the solution
Questions:
Once you have finished trying out the interactive solutions activity, carefully consider the following questions. Then, type or write your answers. When you have your answers, click the questions for feedback.
Once you have finished trying out the interactive solutions activity, carefully consider the following questions. Then, type or write your answers. When you have your answers, click the questions for feedback.
Think: Changing the amount of solute or solvent changes the concentration of a solution.
Interpret: A solution’s concentration decreases if you add more solvent. A solution’s concentration increases if you add more solute, or if you remove solvent.
Decide: To make a dilute solution, you can add a small amount of solute to a solution. To make a concentrated solution you can add a large amount of solute to a solution, or evaporate solvent from the solution.
Make sure you have understood everything in this lesson. Use the Self-Check below, and the Self-Check & Lesson Review Tips to guide your
learning.
Unit A Lesson 4 Self-Check
Instructions
Complete the following 6 steps.
Don't skip steps – if you do them in order, you will confirm your
understanding of this lesson and create a study bank for the future.
- DOWNLOAD the self-check quiz by clicking here .
- ANSWER all the questions on the downloaded quiz in the spaces provided. Think carefully before typing your answers. Review this lesson if you need to. Save your quiz when you are done.
- COMPARE your answers with the suggested "Self-Check Quiz Answers" below. WAIT! You didn't skip step 2, did you? It's very important to carefully write out your own answers before checking the suggested answers.
-
REVISE your quiz answers if you need to. If you answered all the questions correctly, you can skip this step. Revise means to change, fix, and add extra notes if you need to. This quiz is NOT FOR MARKS, so it is perfectly OK to correct
any mistakes you made. This will make your self-check quiz an excellent study tool you can use later.
- SAVE your quiz to a folder on your computer, or to your Private Files. That way you will know where it is for later studying.
- CHECK with your teacher if you need to. If after completing all these steps you are still not sure about the questions or your answers, you should ask for more feedback from your teacher. To do this, post in the Course Questions Forum, or send your teacher an email. In either case, attach your completed quiz and ask; "Can you look at this quiz and give me some feedback please?" They will be happy to help you!
Be a Self-Check
Superhero!
Self-Check Quiz Answers
Click each of the suggested answers below, and carefully compare your answers to the suggested answers.
If you have not done the quiz yet – STOP – and go back to step 1 above. Do not look at the answers without first trying the questions.
You made a concentrated solution of juice, with a large amount of sugar and flavour crystal solute. To make the juice more dilute and better-tasting, you could add more solvent, which is the water.
Glacial acetic acid is a very concentrated solution of acetic acid in water, which makes it is corrosive. Household vinegar is a dilute solution of acetic acid in water, which is why it is not harmful.
Orange juice concentrate must be diluted with water before drinking it. If orange juice is sold as concentrate, it needs less packaging compared to a bottle of ready-to-drink orange juice. Less packaging means that the juice is less heavy to
transport. This means the juice costs less to transport and it is cheaper for the consumer to buy.
Most people would consider tap water to be a dilute solution. You usually can’t see or taste the dissolved salts and minerals, so they have a relatively low concentration in the tap water.
Oven cleaner is corrosive because it is a concentrated solution. If you add water to oven cleaner, it becomes more dilute. Dilute oven cleaner is less corrosive and harmful to the skin.