Yay and Nay. There isn't much research out there about the safety of eating melted ice cream, but if it is still cold it should be safe to eat. I mean, that's basically what soft serve is. Show
However, if the melted ice cream is warm and has been outside for a bit, err on the side of caution and don't eat it. Ice cream is a dairy product, and it's recommended that milk be kept at 45 degrees Fahrenheit or less in order to prevent bacteria from growing. Can You Refreeze Ice Cream?Rica BeltranTechnically you can refreeze ice cream, but it probably will not taste very good. When ice cream melts, the water in it melts too. When you refreeze water, it expands into larger crystals. In addition, ice cream is made up of 30-50% air, thanks to a fluffing process. When it melts, the air that once gave it a fluffy texture escapes. The refrozen ice cream will result in a "rough and crunchy flavor". Yuck. Ice cream is a worldwide food favorite that is always gone too soon. It can't be savored for too long, or else it will end up as a puddle at your feet or melted in the bottom of your bowl. You can ensure your ice cream lasts as long as possible by keeping it in an airtight container at the back of your freezer. This prevents exposure to changing temperatures caused by opening and closing freezer doors. If you're enjoying your treat outside, beware of hot temperatures. Next time someone complains about melted ice cream, make Bill Nye proud with a sciency explaination. Enjoy! Water can exist as a solid (ice), liquid (water) or gas (vapour or gas). Adding heat can cause ice (a solid) to melt to form water (a liquid). Removing heat causes water (a liquid) to freeze to form ice (a solid). When water changes to a solid or a gas, we say it changes to a different state of matter. Even though the water’s physical form changes, its molecules stay the same. Water is a moleculeA molecule is a group of two or more atoms that bond or ‘stick’ together. Water is a molecule. It is made up of two hydrogen (H) atoms and one oxygen (O) atom that are chemically bonded together. The H and O are symbols for the atoms that make up water. This is why people often refer to water as H2O. Water can change from a liquid to a solid or a gas and back to a liquid, but its molecules always stay the same. A water molecule is always H2O whether it is liquid water, ice or water vapour. Nature of scienceNumerous everyday words, like energy, have a different meaning in science. We talk about running out of energy during a race or children having too much energy. Scientists define energy as the potential to do work – such as heating or cooling water to make it change state. Changing states of matter and energyWater, like all other types of matter, requires the addition or removal of energy to change states. A block of ice is solid water. When heat (a form of energy) is added, the ice melts into liquid water. It has reached its melting point – 0°C. Continue to apply heat, and the water will turn into water vapour, which is water in its gaseous state. The water has reached its boiling point – 100°C. If heat is removed from water vapour, the gas cools down and it condenses back into liquid water. Continue to cool the water (by removing heat), and it becomes solid ice. This is its freezing point. Water can change state over and over againYou may have heard that the water you drink today is the same water that dinosaurs drank thousands of years ago. Nature recycles water. It can be melted, frozen and evaporated again and again. There is no loss of water during or after it changes form. Frozen water (ice) takes up more space than liquid water because it is less dense, but when the ice melts, it is the same amount of water as before although some of it may be in the form of water vapour. Related contentChanges of state go beyond melting and freezing. Ice can turn straight to a gas, and gas can change state to plasma or Bose-Einstein condensate. Read about the states of matter. Students will be able to explain that cooling water can change it to ice and that heating ice can change it back to liquid water. Students will be able to explain that this process can also happen to other substances. Students will also be able to explain that heating a substance makes its molecules move faster and cooling a substance makes its molecules move slower. The lesson can also be used to lay a foundation for learning about changes in state and chemical changes which can be further developed in later grades. Key Concepts
NGSS Alignment
Summary
EvaluationDownload the Student Activity Sheet (PDF) and distribute one per student when specified in the activity. The activity sheet will serve as the Evaluate component of the 5-E lesson plan. SafetyBe sure students wear properly fitting goggles. Materials for each group
ENGAGE1. Show a time lapse video of water freezing and ice melting to introduce the idea that cooling and heating can cause a change in a substance.Ask students:
Explain to students that when water freezes, it changes from a liquid to a solid. Show the time lapse video Water Freezing. Note: Tell students that this is a special type of video in which something that takes a long time can be shown in a much shorter time. The freezing of the water in the glass probably took at least six hours. The video was taken for the whole six hours but is shown speeded up so that the freezing process can be shown in about 1 minute. Tell students that this type of video is called “time lapse”. Ask students
Show the time lapse video Ice Melting. Explain that warming ice makes it change from solid ice to liquid water. Note: Students may not realize that the ice is being warmed just by being at room temperature. They may expect to see the ice put on the stove or held over a candle flame. Explain to students that the ice is being warmed because it is at normal room temperature and that room temperature is warmer than the temperature of the ice. Normally ice needs to be in a freezer at a low temperature or outside in cold weather (32 °F or 0°C or lower) to stay frozen as ice. If it is placed on a surface in a room at normal temperature, it is actually being warmed. Explain to students that water can be cooled to make ice and then the ice can be warmed to make liquid water again. Cooling and heating water in this way can make the changes go back and forth. Give each student an Activity Sheet (PDF). EXPLORE2. Have students investigate what happens when butter is heated.Question to Investigate: How does butter change when you warm and cool it?Materials for each group
Have students come to the front of the class. Show students a stick of butter at room temperature. Use a popsicle stick to show that it is soft and can be cut easily. Ask students
Explain to students that when scientists have a question they do an investigation to try to find the answer. Tell students that they can be the scientists and do an investigation to find the answer to the question. Procedure
Note: Tell students that while they heat the butter and stir it, you will stir the same amount of butter in the same type of cup but not heat it. Explain that you want to see if anything happens to the butter from just stirring it, or if it’s the heat that really causes the melting. Ask students:
Note: Let students know that the butter you stirred without heating didn’t change much at all. The change must have been caused by the heat and not just the stirring. 3. Have students investigate what happens when the liquid butter is cooled.Ask Students:
Ask students:
EXPLAIN4. Show an animation to explain that heating makes things move faster and come apart and cooling makes things move slower and connect together.Show the animation Heating and Cooling. Explain that the butter is made up of molecules of fat. When the butter is solid, the molecules are close together and do not move past each other. When the butter is heated, the molecules begin to move and are able to slide past each other and become a liquid. When the liquid butter is cooled, the molecules slow down and reconnect to become a solid again. What causes ice cream to change from solid into a liquid *?- When the mixture is warm the molecules are all spread out and form a liquid. - When the mixture is cooled by the ice the molecules are cold and huddle together forming a solid (ice cream).
Why is my ice cream not solid?Have you added too much sugar, salt or alcohol? They will lower the freezing point of the mixture. And too much of any of these ingredients could stop the ice cream freezing altogether.
Does ice cream turn to liquid?Think back to middle school science class: a solid turns to a liquid because it absorbs energy, and a liquid turns into a gas because it absorbs even more energy. The same thing happens with ice cream.
What happens when ice changes to liquid?When solid ice gains heat, it changes state from solid ice to liquid water in a process called melting. Ice cubes in a cold drink, for example, gradually melt. Each spring you see snow melt into slush and puddles. Sometimes adding heat energy to solid ice causes a change of state from a solid to a gas.
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