Science Key Questions Unit 1.docx

Science Key Questions Unit 1.docx - 1 A gas can change...

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1. A gas can change directly to a solid if the temperature decrease is fast enough through a process called deposition. Gas is made up of many tiny particles that move quickly they are bouncing off each other which means it has no fixed volume or shape. A solid, however, is the opposite where the particles are so close together they cannot move around each other, only vibrate thus giving it a fixed volume and shape. Motions of the particles in both a gas and a solid depend on the temperature. The more heat applied, the more energy the particles must move. If the temperature decreases fast enough, the gas particles rapidly lose any energy they had before until they are forced together by forces of attraction and are essentially frozen in place. An example of this would be outside during the winter. If the air is very cold it often turns to frost on our car windows because the temperature decreases rapidly If the car was warm while it was on. 2. Solids have a fixed volume while liquids do not. The reason for this is because the liquid is always warmer than a solid (example: water is warmer than ice) and as mentioned earlier, heat gives the energy of the particle. The warmer they are, the more energy for them to beat the forces of attraction and move around. In a liquid, the particles are farther apart so they can vibrate and move around from one place to another. Moving particles allow the liquid to flow, therefore liquids have no fixed shape. 3. A gold number being hammered into a flat sheet is a physical change. The physical property is called Malleability which is described as the ability of a solid to be pounded into sheets, and gold being hammered (pounded) into a flat sheet perfectly fits that description. 4. A piece of metal bubbles being placed in acid would be a chemical change. This chemical property would be the bubbles reacting with the acid or undergoing a chemical change. 5. When water boils it is a physical change because they can be observed without changing the identity of the substance. In this case, water boiling is changing its state from a liquid to a gas (steam) but the steam and the liquid are both still water. 6. When salt dissolves in water it is a physical change. The reason for this is because the changes made can be easily reversed as the chemicals that the water is made of stayed the same and the chemicals that made up the salt also stays the same. 7. Baking soda dissolving in vinegar is a chemical change because the baking soda is reacting to the vinegar(acid) by creating bubbles and gas. 8. Most chemical changes cannot be reversed. Chemical changes produce entirely new substances that are not so easily able to be undone. For example, the ashes from wood after I burned the wood in a fire. I would be unable to turn those ashes back into fresh wood that was cut from trees.

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