Year 8 Chemistry Checkpoint 2 PDF

Year 8 Chemistry Checkpoint 2 1. Explain what a physical change is A physical change is when only the physical properties of a substance change the existing bonds DO NOT break and reform and no new substance is created. Physical changes can often be...

Year 8 Chemistry Checkpoint 2 1. Explain what a physical change is A physical change is when only the physical properties of a substance change the existing bonds DO NOT break and reform and no new substance is created. Physical changes can often be reversed. 2. Explain what a chemical change is A chemical change is when the chemical properties of a substance change, the existing bonds break and reform which creates a new substance. Chemical changes cannot be reserved without another chemical reaction. 3. Identify the indicators that a chemical change has happened 1. Bubbles form → indicating a gas has formed 2. Temperature increase or decrease 3. Light produced 4. Heat produced 5. Odour produced 6. Precipitate formed 7. Colour change 4. Explain why cooking toast is NOT a physical change Cooking toast is not a physical change because when toast is cooked, an odour is produced and there is a colour change. These are both indicators that a chemical change has occurred. Additionally, the bread cannot be “untoasted” which means the change cannot be reversed. 5. Draw and label an atom - you need to include the 3 subatomic particles and the charge that each particle has. Please note - it does not matter what type of atom you drew, you should mark yourself whether You identified the 3 subatomic particles correctly; proton, neutron, electron If the charge of each particle was correct If they were put in the correct spot. 6. Classify the particle diagrams below as either an element, compound or mixture and JUSTIFY why Substance A is a compound because it is made up of 2 DIFFERENT types of atoms and they are chemically bonded together GOOD response: Substance B is a mixture because there are 2 different types of matter but they are NOT chemically bonded. BETTER response: Substance B is a mixture of diatomic elements. There are two different diatomic elements physically mixed together, this is evident because they are not chemical bonded. Eg. the blue element is not bonded to the white element. GOOD responses: Substance C is an element because there is the SAME type of matter BETTER response: Substance C is a monatomic element because there is the SAME type of matter and there is only one atom. GOOD response: Substance D is an Substance C is an element because there is only one type of matter BETTER response: Substance C is a diatomic element because even though there are 2 atoms chemically joined, they are the same type of atom. 7. Identify the elements that make up following compounds and how many atoms of each element there are Compounds Element 1 (identify Element 2 (identify Element 3 (identify Element 4 (identify the element and the element and the element and the element and how many atoms) how many atoms) how many atoms) how many atoms) HCl2 1 x Hydrogen 2 x Chlorine CuSO4 1 x Copper 1 x Sulphur 4 x Oxygen NaH2CO3 1x Sodium 2 x Hydrogen 1 x Carbon 3 x Oxygen