Unit 7.2 Study Guide (PDF)

Class-Number: ________ Name: __________________________ ​ ​ Date: ​ Jan 14 Study Guide Unit 7.2 Lesson 1 -3 You need to know: 1.​ What are the criteria; what are constraints? 2.​ What is an open system and a closed system? 3.​...

Class-Number: ________ Name: __________________________ ​ ​ Date: ​ Jan 14 Study Guide Unit 7.2 Lesson 1 -3 You need to know: 1.​ What are the criteria; what are constraints? 2.​ What is an open system and a closed system? 3.​ In Lesson 2, we explore how the MRE heat pad and hand warmer generate heat without a flame. Based on your observations of the materials before and after the reactions, make a claim about whether a new substance is formed. Provide evidence and reasoning to support your claim. 4.​ What is an exothermic process? What is an endothermic process? 5.​ Which four chemical reactions did we explore in Lesson 3? 6.​ There is only one chemical reaction that shows an endothermic process. Which one is that? 7.​ Given measured temperature over time, how do you know if a chemical reaction is over? Explain your answer by drawing a particle model. Review Unit 1: 1.​ What are reactants and what are products? 2.​ How do you know if a chemical reaction occurs? 3.​ How do you know if a chemical equation is balanced? 4.​ What happens to the molecules and atoms when a chemical reaction occurs? 5.​ If a chemical reaction occurs in a closed system, what happened to the total mass of the system? Explain with reasons.  Unit 7.1 Study Guide Key Concept: Gases, liquids and solids are all matter. Matter has mass and takes up space. All matter is made of particles. In a closed system, no matter can get in or out, so the total mass stays the same... even when changes happen to the matter (such as becoming a gas). In an open system, matter can get in or out, so the total mass can change if that happens. Properties don't change for a substance. Properties of a substance include color, smell, density, solubility, viscosity, flammability, state of matter, melting/freezing point, and boiling point, etc. Less dense gases (and liquids) rise when surrounded by denser gases (and liquids). Denser gases (and liquids) sink when surrounded by less dense gases (and liquids). When new substances (molecules) are produced from old substances (molecules), some of the atoms that make up the original substances (molecules) break apart and /or join together to make new types of substances (molecules). Molecules are made of atoms and all the substances in our world are made of very few types of atoms. A substance is made of the same type of molecules (or atoms throughout). The number, type, and arrangement of atoms in the molecules that make up a substance are unique to that substance. In a chemical reaction, the particles that make up old substances can be broken apart and the atoms that make them up can be rearranged to form new molecules to make new substances. In a chemical reaction, the amount of matter at the beginning (in the reactants) is the same amount of matter at the end of the reaction (in the products). This is because all of the atoms we started with are still there. No new atoms can appear that weren’t there to start with. Chemical reactions involve the process of rearrangement of the particles that make up the matter in the system. A balanced chemical reaction conserves mass, with the number of each type of atom equal on both sides of the equation.  Important Vocabulary ​ An exothermic reaction is a chemical reaction in which energy is released in the form of heat and/or light. The release of energy during these reactions can make the surroundings feel warm or hot. ​ An endothermic reaction is a type of chemical reaction in which energy is absorbed. The absorption of energy during these reactions can make the surroundings cooler. ​ Closed system. a system in which mass cannot be exchanged but energy can. ​ Open system. a system in which both mass and energy can be exchanged. ​ Reactant, n. a substance that undergoes a change in a chemical reaction ​ Product, n. a substance produced by a chemical reaction, different from the reactants ​ Atom, n. basic unit of matter consisting of a positively charged nucleus and negatively charged electrons ​ Molecule, n. A molecule is a group of two or more atoms that are held together by chemical bonds. ​ Substance - a particular kind of matter with uniform properties. (A molecule is a substance.) ​ Mixture - a blend of two or more substances ​ Compound - a substance that is composed of two or more separate elements. ​ Density: the amount of matter in a volume of a substance or object, often measured in grams per milliliter (g/mL) or kilograms per cubic meter (kg/m3) ​ Flammability: how easy a substance catches on fire