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Description
Flashcards by Ahmed Almohammed, updated more than 1 year ago
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Created by Ahmed Almohammed
almost 8 years ago
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| Question | Answer |
| What is the difference between a physical and chemical change? | In a physical change, there are no new substances produced. while in a chemical change, new substances are produced. |
| Why is it that physical changes can often be easily reversed? | Because the substance before and after the change is exactly the same. |
| What is the simplest example of a physical change? | The simplest example is one that changes the shape or form of a substance. |
| What is the difference between expansion and contraction? | In an expansion, the volume of the object increases and its density decreases. While in contraction, the object's volume decreases and its density increases. |
| What is melting? | When a solid is heated enough, it will melt and change into a liquid. This process of the solid changing into a liquid is called melting. |
| What happens when liquid water is put in the freezer? | The liquid water gets cooled enough to change into a solid. This process is called freezing. |
| What is a solution? | When a solute is dissolved in a solvent, they form a solution. |
| What happens in a solution? | The smallest particles of the solute mix and spread evenly throughout the smallest particles of the solvent. |
| What are the four indications of a chemical change? | |
| Why is it that change in colour is likely a chemical change? | This is because the new substance produced by the chemical change has a different colour to what you started to see |
| What is an example of a physical change that can also cause a change in colour? | When the snow melts to form liquid water it turns from white to colourless. |
| What indicates the production of gas in a chemical change? | A gas produced during a chemical change may be observed as bubbles, a new smell or even smoke. |
| What indicates that a chemical change occurred when two solutions mix? | A new solid is produced when two solutions are mixed. The solid precipitates out of the solution and sinks to the bottom. This solid is known as the precipitate. |
| Why is it that light or change in temperature indicates a chemical change? | This is because some chemical changes release energy in the form of heat light and or both. Such as a firework. |
| Why does a chemical ice pack feel icy cold? | This is because this chemical ice pack uses a chemical change that absorbs a lot of heat and energy, causing it to feel so icy cold. |
| What is an example of a physical change that causes a change in temperature? | When you sweat you feel cooler because the moisture evaporates and absorbs some heat from your skin. |
| Why is it that recycling is a series of physical changes and not chemical changes? | In most cases when a substance is recycled, the form of the substance may change but the substance itself stays the same. Therefore, the recycling process is simply a series of physical change. |
| Why is it that heating the air inside a hot-air balloon allows it to float? | Heating the air inside the balloon causes it to expand and become less dense than the air outside. As a result, the balloon floats. |
| Give an example of an exothermic reaction. | Fires and explosives are examples of extreme exothermic reactions. They release large amounts of heat and light energy. |
| Why is aluminium recycled? | Because recycling aluminium is cheaper than making it from new material. |
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