Year 10 Advanced Chemistry Revision -ANSWERS Name: _____________________________ What are the differences between physical and chemical changes? Physical change Chemical Reaction Change of what? Changes of states Sound, Light, Heat is given Evidences of chemical Changes of shapes out (exothermic), Heat is reactions Temporary changes of colours absorbed (endothermic), New substance formed or No new substance is formed New substances (products) not are formed from reactants Reversible or not Reversible (change back) Irreversible (not changing back) Example Ice becomes water and steam Making a frying an egg; on heating; stepping on a can; lighting up a sparkler Heating iodine to purple vapour (sublimation) Atomic Structures sub-atomic particles – Proton Electron Neutron Where can you it? Inside the nucleus Surrounding the Inside the nucleus Inside nucleus or nucleus surrounding nucleus Charge neutral, Positive charge Negative charge No charge – positive or negative = Neutral Mass 1 unit or 1 unit 0 (very little mass) 1 unit – negligible Function or To attract electrons To exchange and To hold the protrons importance with other together inside the atoms to form nucleus compounds Different types of metals: Types Examples Remarks Alkali metals Li, Na, K 1 valence electron Alkaline earth metals Be, Mg, Ca 2 valence electrons Transition metals Ni, Fe, Ag, Au, Cu Variable valence electrons Other metals Al, Pb 3 valence electrons a) What is a molecule? A molecule is the smallest part of a substance made of 2 or more atoms chemically bonded together, can be the same kind (like diatomic elements) or different kind forming compounds. b) Can an element exist as molecule? Give all the examples. Yes those 7 diatomic elements – Have No Clever Or Bright Friends” “I Iodine I2, Hydrogen H2, Nitrogen N2, Chlorine Cl2, Oxygen O2, Bromine Br2, Fluorine F2, c) Why do noble gases exist as atoms only but not molecules? Noble Gases (Group 8 elements) have 8 electrons (except He 2) in the outermost electronic shells being full shell have octet rule very stable, unlikely to bond or – – – react with other elements.
Year 10 Advanced Chemistry Revision -ANSWERS Name: _____________________________ What are the differences between physical and chemical changes? Physical change Chemical Reaction Change of what? Evidences of chemical reactions Changes of states Changes of shapes Temporary changes of colours Sound, Light, Heat is given out (exothermic), Heat is absorbed (endothermic), New substance formed or not No new substance is formed New substances (products) are formed from reactants Reversible or not Reversible (change back) Irreversible (not changing back) Example Ice becomes water and steam on heating; stepping on a can; Heating iodine to purple vapour (sublimation) Making a frying an egg; lighting up a sparkler Atomic Structures – sub-atomic particles Proton Electron Neutron Where can you it? Inside nucleus or surrounding nucleus Inside the nucleus Surrounding the nucleus Inside the nucleus Charge – neutral, positive or negative Positive charge Negative charge No charge = Neutral Mass – 1 unit or negligible 1 unit 0 (very little mass) 1 unit Function or importance To attract electrons To exchange and with other atoms to form compounds To hold the protrons together inside the nucleus Different types of metals: Types Examples Remarks Alkali metals Li, Na, K 1 valence electron Alkaline earth metals Be, Mg, Ca 2 valence electrons Transition metals Ni, Fe, Ag, Au, Cu Variable valence electrons Other metals Al, Pb 3 valence electrons a) What is a molecule? A molecule is the smallest part of a substance made of 2 or more atoms chemically bonded together, can be the same kind (like diatomic elements) or different kind forming compounds. b) Can an element exist as molecule? Give all the examples. Yes – those 7 diatomic elements “I Have No Clever Or Bright Friends” Iodine I2, Hydrogen H2, Nitrogen N2, Chlorine Cl2, Oxygen O2, Bromine Br2, Fluorine F2, c) Why do noble gases exist as atoms only but not molecules? Noble Gases (Group 8 elements) have 8 electrons (except He 2) in the outermost electronic shells – being full shell – have octet rule – very stable, unlikely to bond or react with other elements.
10Chemistry_adv_Revision.docx