## That"s A N(ice) Temperature

### Overview

In this 30-minute companion task to The Melting Point, teams of kids periods 8 to 13 experiment to find the melting and also freezing points of water and also ice.

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### What"s the Point?

Water deserve to exist in different states; ice is the solid state of water. Physical properties are characteristics of a substance. They perform not adjust. Physical properties encompass color, smell, freezing/melting point, and thickness. The freezing allude of water is the very same as the melting allude of ice: 32°F (0°C).

### Materials

For each child

His/her envelope of mobile pieces Pencil or pen

For each team of 4 to 6 children:

1 thermometer that is conveniently read, preferably in both Celsius and also Fahrenheit, and that is safe for use by kids 1 (7-ounce) cup or larger plastic container 1 (8-ounce) clear plastic cup Enough foil to cover the peak — however not the sides — of the cup ~5 cups of ice cubes (not crushed ice) (Make sure the ice cubes are loose and also not stuck together.) 1 cup of crushed ice ~2 cups of rock salt (the sort supplied to make ice cream) 1 timer, stopwatch, watch, or clock with a 2nd hand Paper Towels

For the facilitator:

A permanent marker 2 task set-ups to use for demonstration objectives (One will be the same to the children"s, the various other will certainly include all actions but salt will certainly be omitted.)

### Preparation

Check the thermometers to ensure that they are working. Prepare the activity set-ups you will use for demonstration throughout the task.

### Activity

Introduce the activity by stating the freezing temperatures of water and also the melting temperatures of ice. At what temperature does water freeze? 32°F (0°C). Ask them around their experiences with ice. Wright here carry out they uncover it? In their freezers. How cold is the freezer? Have they ever before observed ice freezing outside? What was the temperature? The youngsters may not recognize the numerical answer, yet they will certainly uncover it in the task. Explain to the kids that this is referred to as the "Freezing Point" of water. Ask the youngsters to make predictions about the melting point of ice. At what temperature execute they think ice melts? Aobtain, the kids may or may not understand. Invite the kids to think around their experiences. Would ice melt on a hot summer day outside in the Sun? What might that heat external temperature be? Would it melt in the room in which the youngsters are at this moment? Probably (hopefully!). What is the temperature of the room?
Facilitator"s Note: Changes in temperature deserve to cause water to change state, and also these transforms happen at certain temperatures. Fresh water transitions between the solid and also liquid says at 32°F (0°C) at sea level. At temperatures below 32°F (0°C), liquid water freezes; 32°F (0°C) is the freezing point of water. At temperatures over 32°F (0°C), pure water ice melts and also changes state from a solid to a liquid (water); 32°F (0°C) is the melting point. For most substances, the melting and freezing points are about the same temperature.
Facilitator"s Note: Contrary to our instincts, the melt water"s temperature will certainly not rise as long as ice is existing. The heat room continues to include energy to the cup, yet every one of that energy proceeds to go right into melting the ice fairly than raising the temperature. Once all the ice has melted, that energy can begin to rise the water"s temperature.
Ask the children exactly how they could re-freeze the melted water without placing the cup earlier into the freezer. Is there somepoint they can carry out, based upon what they learned in the Melting Point Activity? Do all substances have actually the same melting point?Invite the youngsters to record their responses in their Ice Investigator Journals. Provide the children through the larger container, ice cubes, foil, and salt. Demonstprice the various measures of the experiment and have the youngsters repeat what you do. Cover the entire bottom of the large container via 1/3 of the ice cubes. Cover the height of the cup that has crushed ice and water from the previous experiments with foil. Place it in the middle of the container on optimal of the ice. Sprinkle fifty percent of the salt over the ice cubes. Create an additional layer of ice over the salt utilizing 1/3 of the ice cubes. Sprinkle this layer via the rest of the salt. Cover it with the staying 1/3 of the ice cubes. Make sure that the height of the cup with crumelted ice is a small above the layers of ice and also salt.Remove the foil from the cup, area the lid on the container, and enable the experiment to sit undisturbed for about 10 minutes. As the facilitator, repeat the experimental style for one additional container, yet leave out the salt. This container will certainly host only ice cubes and also the cup of cruburned ice and also melt. Share what you are doing with the youngsters. Invite the kids to predict what will occur to the cups of cruburned ice that are in the containers of salt and ice. Will the crushed ice proceed to melt? Will it sheight melting? Will it freeze? What will occur to the cup of crushed ice in the huge container that does not have any salt?
Facilitator"s Note: Adding salt lowers the melting point of water. Pure water and ice, retained insulated from the warmth external people, concerned equilibrium over time. On a molecular level, water molecules are freezing onto the ice at the very same price as they are melting off of it. The whole water/ice solution is at the melting/freezing suggest, 32°F (0°C). Adding rock salt or any kind of substance that dissolves in water disrupts this equilibrium. Fewer water molecules are interacting via the ice at any offered moment, so the freezing price is slowed. The salt has no result on the melting rate, so more melting occurs than freezing — melting "wins" and the ice melts. In doing so, warm power is provided to break the hydrogen bonds that hold the molecules in the ice together. In other words, the ice "supplies up" some warmth from the solution and the temperature drops. Melting and freezing aget enhance rates ("tie") when the temperature has dropped to the brand-new melting allude. The better the amount of salt, the reduced the freezing point (to a point; when tright here is enough salt that no even more will certainly disfix, the freezing allude no longer decreases). Ocean water is around 3.5% salt; sea water freezes at around 28°F (-2°C). A 10% salt solution freezes at about 20°F (-6°C), and also a 20% solution freezes at 2°F (-16°C).