Year 8 Autumn Assessment Revision Notes and Practice Questions PDF

Year 8 Autumn Assessment Revision Notes Atoms Atoms are the smallest particles of matter that still have the properties of that substance. They are made up of protons, neutrons, and electrons. Protons are positively charged. Neutrons have no charge. Electrons are...

Year 8 Autumn Assessment Revision Notes Atoms Atoms are the smallest particles of matter that still have the properties of that substance. They are made up of protons, neutrons, and electrons. Protons are positively charged. Neutrons have no charge. Electrons are negatively charged. Elements Elements are pure substances made up of only one type of atom. The number of protons in an atom determines the element. Each element has a unique chemical symbol. Examples of elements include: hydrogen (H), oxygen (O), carbon (C), and gold (Au). Periodic Table The periodic table is a table that organizes elements based on their properties. Elements are arranged in periods (horizontal rows) and groups (vertical columns). Elements in the same group have similar chemical properties. The atomic number of an element is the number of protons in its nucleus. Compounds Compounds are pure substances made up of two or more different elements chemically combined. The chemical properties of a compound are different from the elements that make it up. Compounds have a chemical formula that shows the ratio of atoms in the compound. Examples of compounds include: water (H₂O), carbon dioxide (CO₂), and sodium chloride (NaCl). Mixtures Mixtures are substances made up of two or more different substances that are not chemically combined. The components of a mixture can be separated by physical means. Mixtures can be homogeneous (uniform throughout) or heterogeneous (not uniform throughout). Examples of mixtures include: air, saltwater, and chocolate chip cookies. Key Concepts to Remember: The difference between atoms, elements, compounds, and mixtures. The structure of an atom. The periodic table and its organization. The properties of elements and compounds. The difference between homogeneous and heterogeneous mixtures Chemical Reactions A chemical reaction is a process where one or more substances (reactants) are changed into different substances (products). Chemical properties of substances change during a chemical reaction. Physical properties of substances may also change, but this alone does not indicate a chemical reaction. Signs of a chemical reaction include: o Gas production (e.g., bubbles) o Precipitate formation (e.g., solid forming in a solution) o Color change o Energy change (e.g., heat released or absorbed) Reactivity Reactivity is a measure of how easily a substance undergoes a chemical reaction. More reactive substances react more readily with other substances. Less reactive substances react less readily. Reactivity can be influenced by factors such as: o Temperature (higher temperature often increases reactivity) o Concentration (higher concentration often increases reactivity) o Surface area (larger surface area often increases reactivity) o Presence of a catalyst (a catalyst speeds up a reaction without being consumed) Types of Chemical Reactions Combustion: A reaction with oxygen that releases heat and light. Decomposition: A reaction where a single compound breaks down into simpler substances. Synthesis: A reaction where two or more simple substances combine to form a more complex substance. Neutralization: A reaction between an acid and a base to form a salt and water. Word Equations Word equations represent chemical reactions using the names of the reactants and products.  For example: o Hydrogen + Oxygen → Water o Magnesium + Hydrochloric acid → Magnesium chloride + Hydrogen Key Concepts to Remember: The definition and signs of a chemical reaction. The concept of reactivity and its influencing factors. The different types of chemical reactions. How to write word equations for chemical reactions. 20 Questions and Answers Based on the Notes Atoms, Elements, Compounds, and Mixtures 1. What is the smallest particle of matter that still has the properties of that substance? o Answer: Atom 2. Name the three particles that make up an atom. o Answer: Protons, neutrons, and electrons 3. What is the difference between an element and a compound? o Answer: Elements are pure substances made up of only one type of atom, while compounds are made up of two or more different elements chemically combined. 4. Give an example of a compound. o Answer: Water (H₂O) 5. What is the difference between a homogeneous and a heterogeneous mixture? o Answer: A homogeneous mixture has a uniform composition throughout, while a heterogeneous mixture has a non-uniform composition. Periodic Table 6. How are elements organized in the periodic table? o Answer: Elements are arranged in periods (horizontal rows) and groups (vertical columns). 7. What does the atomic number of an element represent? o Answer: The number of protons in its nucleus. 8. Elements in the same group have similar ________ properties. o Answer: Chemical Chemical Reactions 9. What is a chemical reaction? o Answer: A process where one or more substances (reactants) are changed into different substances (products). 10. Name three signs of a chemical reaction. Answer: Gas production, precipitate formation, color change 11. What is reactivity? Answer: A measure of how easily a substance undergoes a chemical reaction. 12. How can temperature affect the reactivity of a substance? Answer: Higher temperature often increases reactivity. Types of Chemical Reactions 13. What is a combustion reaction? Answer: A reaction with oxygen that releases heat and light. 14. What is a decomposition reaction? Answer: A reaction where a single compound breaks down into simpler substances. 15. What is a synthesis reaction? Answer: A reaction where two or more simple substances combine to form a more complex substance. 16. What type of reaction occurs between an acid and a base? Answer: Neutralization Word Equations 17. What is a word equation? Answer: A representation of a chemical reaction using the names of the reactants and products. 18. Write a word equation for the reaction between hydrogen and oxygen. Answer: Hydrogen + Oxygen → Water 19. What is the difference between a reactant and a product in a chemical reaction? Answer: Reactants are the substances that undergo a chemical change, while products are the new substances formed. 20. Write a word equation for the decomposition of water. Answer: Water → Hydrogen + Oxygen