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Description
Flashcards by Farha Idrees, updated more than 1 year ago
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Created by Farha Idrees
almost 8 years ago
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| Question | Answer |
| How many elements are there on Earth? | There are 92 naturally occurring elements on Earth. |
| What are elements? | Elements are pure substances with only one type of atom, such as copper, carbon or gold. |
| The particles inside copper are called ______ atoms. All these ______ atoms are the same. | copper, copper |
| Gold is made of _____ ______ | Gold is made of gold atoms. |
| True or False: Everything is made from atoms. | True. |
| What are molecules? | When atoms of the same element are joint together. For example, in oxygen. This is why we write oxygen as O2, since it has two atoms to make a molecule. |
| Each element is given its own chemical symbol. These are usually one or two letters long. - What is the symbol for hydrogen? | hydrogen --> H |
| What is the chemical symbol for magnesium? | Magnesium --> Mg ***Rember: every chemical symbol starts with a capital letter, with the second letter written in lowercase. So mg, mG, or MG would be wrong. |
| What two main groups are the elements divided into? | Metals and non-metals |
| Give the properties of metals. (ignore the exceptions) | -solid at room temperature -shiny if polished -conducts heat and electricity -bends without breaking -can stretch into wires |
| Give the properties of non-metals. (ignore the exceptions) | -solids, liquids, gases at room temperature -not shiny -doesn't conduct electricity or heat -breaks easily -cannot stretch easily |
| define a mixture | mixture: two or more substances that are not chemically joined |
| What are the four rules for mixtures? | 1. they can be separated by physical methods 2. the mixtures have the properties of the substances in the mixture 3. can be made using different amounts of each substance 4. no chemical change occurs when mixing |
| What is a compound? | a compound is a substance that contains atoms of two or more different elements that are chemically joined together |
| Give an example of a compound | -Water: a compound of oxygen and hydrogen -Carbon dioxide: a compound of carbon and oxygen |
| What is the word equation for carbon dioxide? | carbon + oxygen = carbon dioxide |
| What does 'di' in dioxide mean? | It means that the chemical has two oxygen atoms. For example sulphur dioxide has one sulphur atom and two oxygen atoms. di = two oxide = oxygen |
| What is the symbol equation for lead dioxide? (lead = Pb) | Pb + O2 = PbO2 |
| Elements can be joined in ratios. For example., say you had one red brick joined onto two yellow bricks. What would the ratio of red to yellow be? | The ratio of red to yellow bricks would be 1:2. Elements can be joined in a similar way. |
| READ: When lead and oxygen combine they make lead oxide. But, it is more complicated than this because there are three different lead oxides. These are the three: | yellow = PbO = 1:1 brown = PbO2 = 1:2 red = Pb3O4 = 3:4 |
| What is the Law of Multiple Proportions? | The law stating that when elements combine, the number of particles of each are always in a small number ratio. This means that its unlikely for you to find a ratio such as 1:2:7 or even 25:63. |
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