Temperature and solubility - GreatSchools

1 062-063-KS2U 23/2/06 2:11 PM Page 63 (Cyan plate) 63 Temperature and solubility Background knowledgeIt is easier to dissolve soluble substances in warm water than in cold , heat increases the solubility of some substances more than of activityMake a line graph to plot the data from the table. Be sure to connect all thepoints after they are plotted. The data shows the solubility of table salt andof Epsom salts as Temperature ( C) solubility (g/jug)405060 Temperature ( C)2030405060 Salt1012141618 Epsom salts2030405055 Amount dissolvedper jug(in grams)1Do you see a relationship between Temperature and the solubility of tablesalt? Explain. 2Is this relationship the same for Epsom salts? any differences Temperature has on the solubility of Epsom saltsas compared to table salt . Science investigation 062-063-KS2U 23/2/06 2:13 PM Page 63 (Black plate) You can make rock candy by dissolving a lot of sugar (2 cups) in a cup of boiling water.

2 Let the solution cool and pour it into plastic cups, filling each half way. Tie 12 cm of plain dental floss in the center of a pencil. Place the pencil over a cup and let the floss drop into the solution. Repeat for the other cups. Observe what happens over two weeks. Draw diagrams and explain your observations. Take extra care - ask an adult to supervise you. Dorling Kindersley Limited [2010] Dorling Kindersley Limited [2010]Prepare different solutions of salt water and time howlong it takes each to freeze. The water can be placedin the freezer and checked at regular intervals. Use aCelsius thermometer to take the solution s temperaturewhen it begins to It s freezing! Background knowledgePure water freezes at 0 C. Water with substances dissolved in it (a solution)freezes at a lower Temperature .

3 Some substances, such as candle wax, freeze(solidify) at temperatures above 0 C. Other substances, such as vegetable oil,freeze at a Temperature below 0 C. The Temperature at which a substancefreezes is called its freezing activityThe freezing points of different liquids are shown in the bar graph at the bar graph, which substance will be a solid on a winter s daybut a liquid on a summer s day? The rhyme below will help you. 5, 10, and 21 winter, spring, and summer sun. Science investigationLiquidsTemperature ( C)alcoholwaterantifreezepropanolglycerin methylated spirits 114 C0 C 13 C 28 C18 C 94 C 140 120 100 80 60 40 20020 Glycerin it freezes at tempretatures below 18 C. Try different water-soluble markers. Ink in thesemarkers is a color mixture; black ink is composed of anumber of dyes such as red, blue, yellow, and paper separates the ink mixture because the inksolutes are absorbed at different rates.

4 62 Water scienceBackground knowledgeTap water contains substances (solutes) already dissolved in it. The amountand type of dissolved substances depend on where you live. This is one of thereasons that tap water tastes different in different areas. You can find out howmuch solute is dissolved in water by pouring a small amount into a glass andallowing it to evaporate. The white ring or scale left behind in the glasscontains minerals that were dissolved in the water. Water that contains a lot ofdissolved substances is called hard water, while water that contains veryfewdissolved substances is called soft water. Science activityTiah had a fish tank. As the water evaporated, she would add more noticed a line of white scale on the inside of the fish tank where thewater had evaporated. Explain Tiah s investigationTap water has minerals in it.

5 When the water evaporates, theminerals are left behind. These minerals create the whitescale on the fish salt solutions with different concentrations,then place the boat in each solution to see how high itfloats. The more salt added to the water, the greaterits buoyancy (density). As the water s density increases,its buoyant force on salt water Background knowledgeMixing substances together can cause their properties to change. Adding salt towater makes the water salty. salt water boils at a higher Temperature than freshwater and freezes at a lower Temperature . Buoyancyis the upward pushingforce of a fluid. Objects float more easily in salt water than in fresh water,because salt water is more buoyant. This is also why it is easier to swim insalt water than in fresh activityLook at the pairs of pictures.

6 Which picture in each pair shows sea waterand which shows fresh water?If you added sand to water, would it boil at a higher Temperature ? investigation100 C105 C110 C95 C105 C110 C100 C95 C fresh watersea watersea waterfresh waterNo, because sand will not dissolve in candy is made from a supersaturated sugarsolution. Document candy formation in dailyobservations and diagrams. Food coloring can be usedto color the candy. Some heat packs are supersaturatedsolutions that release heat when crystallizing. 63 Temperature and solubility Background knowledgeIt is easier to dissolve soluble substances in warm water than in cold , heat increases the solubility of some substances more than of activityUse a line graph to plot the data on the graph. Make sure to connect all thepoints after they are plotted.

7 The data shows the solubility of table salt andof Epsom salts as Temperature ( C)2030405060 Salt1012141618 Epsom salts2030405055 Amount dissolvedper jug(in grams)1Do you see a relationship between Temperature and the solubility of tablesalt? Explain. 2Is this relationship the same for Epsom salts? any differences Temperature has on the solubility of Epsom saltsas compared to table salt . Science investigationYes, the relationship is the same for Epsom solubility of Epsom salt is more greatly affected ( C) solubility (g/jug)40506050 Epsom saltsSaltYes, as the Temperature increases, the salt becomes more 23/2/06 1:51 PM Page 111 (Black plate) Rock candy is made from a supersaturated sugar solution. Document candy formation in daily observations and diagrams. Food coloring can be used to color the candy.

8 Some heat packs are supersaturated solutions that release heat when crystallizing. Dorling Kindersley Limited [2010]