5.4 exothermic and endothermic reactions

This document defines the classification of matter. There are two main categories: pure substances and mixtures. Pure substances include elements, which are made of only one type of atom, and compounds, which are two or more elements chemically bonded together. Mixtures contain two or more pure substances mixed together without chemical bonding. Mixtures can be either heterogeneous, where the parts can be seen, or homogeneous, where the parts cannot be seen. Heterogeneous mixtures are less pure than homogeneous mixtures.

A chemical reaction involves the transformation of reactants into different products through rearrangement of atoms. Chemical reactions conserve mass as atoms are not destroyed or created, but instead are reorganized into new substances. Balancing chemical equations ensures the same number and type of atoms are on both sides of the reaction.

1) Displacement reactions can be classified as metal-metal displacement reactions or metal-nonmetal displacement reactions. 2) In metal-metal displacement reactions, more reactive metals displace less reactive metals according to the reactivity series. For example, copper displaces iron when an iron bar is placed in copper sulfate solution. 3) In metal-nonmetal displacement reactions, metals can displace hydrogen from water, with more reactive metals like sodium displacing hydrogen even at room temperature, while less reactive metals like iron only displacing hydrogen when heated.

This document provides an overview of chemical reactions and energetics for a 10th grade IGCSE course. It discusses exothermic and endothermic reactions in relation to energy changes and temperature. It also covers the factors that affect reaction rates, including concentration, particle size, catalysis, and temperature. The document defines oxidation and reduction in terms of electron transfer and identifies redox reactions. It provides examples of exothermic and endothermic reactions and discusses how catalysts can lower the activation energy and increase reaction rates. Interactive links are included to illustrate and reinforce the concepts.

A mole is the standard unit used to measure very large quantities of small particles like atoms and molecules. It represents 6.02 x 1023 particles, which is an immense number that is difficult to comprehend. The molar mass of an element or compound is the mass in grams of one mole of that substance. To find molar mass, one does an atom inventory of the substance and multiplies the number of each type of atom by its atomic mass on the periodic table, then sums the results.

The document outlines 5 main types of chemical reactions: synthesis, decomposition, single replacement, double replacement, and combustion. It provides examples of each type of reaction and describes their key characteristics. Synthesis reactions combine two or more reactants to form one product. Decomposition reactions involve a single reactant breaking down into multiple products. Single replacement reactions involve one element replacing another in a compound. Double replacement reactions involve two compounds swapping parts to form two new compounds. Combustion reactions involve organic compounds burning in oxygen to produce carbon dioxide and water.

1) A chemical equation is a symbolic representation of a chemical reaction using element symbols and formulas to show reactants and products. 2) Chemical equations must be balanced so that the same number of each type of atom is on both sides of the reaction arrow. 3) To balance equations, coefficients are placed in front of formulas to adjust the relative numbers of elements and compounds until both sides have equal quantities.

The document describes the main types of chemical reactions: synthesis reactions where two or more reactants form one product, decomposition reactions where one reactant breaks down into multiple products, replacement reactions including single replacement where one element replaces another in a compound and double replacement where ions switch between compounds, and combustion reactions where a substance reacts with oxygen releasing energy.

The document discusses rate of reaction and factors that affect it. It defines rate of reaction as the change in amount of reactants or products per unit time. It describes several factors that affect rate based on collision theory, including surface area, concentration, temperature, catalysts, and pressure. It gives examples of how scientific understanding of rate of reaction enhances quality of life, such as refrigeration, pressure cooking, cutting food into smaller pieces, making margarine, and burning coal.