| The scientific principle stating that in a chemical reaction, no atoms are lost or made, only rearranged. | Law of Conservation of Mass |
| What does the law of conservation of mass state? | The law of conservation of mass states that no atoms are lost or made in a chemical reaction; they are only rearranged. |
| The basic units of matter that make up all substances, consisting of a nucleus containing protons and neutrons, with electrons orbiting around it. | Atoms |
| Why must the mass of products at the end of a chemical reaction equal the mass of reactants at the start? | Because no atoms are lost or made in a chemical reaction, according to the law of conservation of mass, so no mass is lost or made. |
| Chemical equations that use symbols and formulas to represent the reactants and products in a chemical reaction. | Symbol Equations |
| What do symbol equations show in a chemical reaction? | Symbol equations show which elements take part in a chemical reaction. |
| The substances present at the beginning of a chemical reaction, which undergo chemical change to form products. | Reactants |
| Where are the formulae of the reactants and products placed in a symbol equation? | The formulae of the reactants are placed on the left side of the arrow, and the formulae of the products are placed on the right side. |
| The scientific principle stating that the total mass of the reactants in a chemical reaction must equal the total mass of the products. | Law of Conservation of Mass |
| What principle ensures that symbol equations must be balanced? | The law of conservation of mass ensures that symbol equations must be balanced. |
| Symbol equations where the number of atoms of each element is the same on both sides of the equation. | Balanced Equations |
| Why is the example equation provided considered balanced? | It's balanced because both sides of the equation have 2 sodium (Na) atoms and 2 chlorine (Cl) atoms. |
| Chemical equations that represent the reactants and products in a chemical reaction using symbols and formulas. | Symbol Equations |
| How are symbol equations balanced? | Symbol equations are balanced by adding numbers (multipliers) in front of chemical formulas. |
| What is the first step in balancing a symbol equation? | The first step is writing down the chemical formula for each substance involved in the equation. |
| Why is the provided equation initially considered unbalanced? | It is unbalanced because there are 2 oxygen atoms on the left but only 1 on the right. |
| Numbers added in front of chemical formulas in a symbol equation to balance the equation. | Multipliers |
| What role do multipliers play in balancing a symbol equation? | Multipliers are used to multiply the number of atoms of each element by a specific factor to balance the equation. |
| A diatomic molecule composed of two hydrogen atoms. | Hydrogen (H2) |
| What multiplier is added in front of H2O to balance the oxygens atoms in the provided equation? | A multiplier of 2 is added in front of H2O. |
| A diatomic molecule composed of two oxygen atoms. | Oxygen (O2) |
| What multiplier is added in front of H2 to balance the hydrogen atoms, therefore the whole equation? | A multiplier of 2 is added in front of H2. |
| How do multipliers ensure that both sides of the equation have an equal number of atoms of each element? | Multipliers adjust the number of atoms of each element in chemical formulas to ensure balance in the equation. |
| Why can't equations be balanced by changing the numbers within a chemical formula? | Equations can't be balanced in this way because changing the numbers within a formula would result in a different chemical compound. |
| Why can't the equation for making water be balanced by changing the numbers within the formula like this: H2O2? | H2O2 is the formula for hydrogen peroxide, not water, so changing the numbers within the formula results in a different chemical compound. |
| A chemical equation in which the number of atoms of each element is the same on both sides, ensuring the conservation of mass. | Balanced Equation |
| What principle ensures that the sum of the relative formula masses (Mr) of the products equals the sum of the Mr of the reactants in a balanced equation? | The law of conservation of mass ensures that the sum of the Mr of the products equals the sum of the Mr of the reactants in a balanced equation. |
| The scientific principle stating that the total mass of the reactants in a chemical reaction must equal the total mass of the products. | Law of Conservation of Mass |
| What is the first step in demonstrating the conservation of mass in a chemical reaction? | The first step is to add up the relative formula masses of the reactants. |
| The substances present at the beginning of a chemical reaction that undergo chemical change to form products. | Reactants |
| What is the second step in demonstrating the conservation of mass in a chemical reaction? | The second step is to add up the relative formula masses of the products. |
| The substances formed as a result of a chemical reaction. | Products |
| How can you confirm that mass has been conserved in a chemical reaction using relative formula masses? | Mass has been conserved if the sum of the Mr of the reactants equals the sum of the Mr of the products. |
| A system in which no matter enters or exits, and thus the total mass remains constant. | Closed System |
| What is a characteristic of a reaction that occurs in a closed system? | In a closed system, nothing enters or exits the system during the reaction. |
| A chemical reaction in which two solutions react to form an insoluble solid called a precipitate. | Precipitation Reaction |
| What happens in a precipitation reaction? | In a precipitation reaction, two solutions react to produce an insoluble solid, known as a precipitate. |
| A solid that does not dissolve in a particular solvent. | Insoluble Solid |
| What occurs when a precipitation reaction takes place in a closed flask? | The reaction occurs in a closed system where nothing enters or exits the flask. |
| A chemical compound consisting of potassium and iodine ions, often used in chemical reactions. | Potassium Iodide (KI) |
| What is an example of a precipitation reaction involving potassium iodide and silver nitrate? | An example is when a colourless solution of potassium iodide reacts with a colourless solution of silver nitrate to form a yellow solid, silver iodide, and potassium nitrate. |
| The principle stating that the total mass of the reactants in a chemical reaction must equal the total mass of the products. | Law of Conservation of Mass |
| How does the law of conservation of mass apply to reactions in a closed system? | In a closed system, the mass remains constant because no matter enters or exits the system, and the number and type of atoms within the system do not change; they simply rearrange to form different compounds. |
| A system in which reactants and products are not contained, allowing them to interact with the surrounding environment. | Non-enclosed System |
| What is a characteristic of reactions that occur in non-enclosed systems? | Reactants from the environment can enter the system, and reactants and products can escape into the environment. |
| A state of matter characterized by particles that are widely spaced and move freely, allowing them to fill the shape and volume of their container. | Gas |
| What types of substances are typically involved in reactions in non-enclosed systems? | Gases are typically involved because their particles are free to move around and can expand to fill any container. |
| The increase in volume or size of a substance when subjected to changes in temperature, pressure, or other factors. | Expansion |
| Why do gases expand in non-enclosed systems? | Gases will expand to fill any container, and in non-enclosed systems, they can expand out into the surrounding environment. |
| The surroundings or external conditions in which a system exists or operates. | Environment |
| What types of particles are involved in reactions in non-enclosed systems, and why? | Gaseous particles are involved because they are free to move around and can interact with the environment in non-enclosed systems. |
| Gases present in the Earth's atmosphere, such as oxygen, nitrogen, and carbon dioxide. | Atmospheric Gases |
| What can cause the mass of the products to appear greater than the mass of the reactants in some reactions? | One of the reactants being a gas found in the atmosphere can cause the mass of the products to appear greater than the mass of the reactants. |
| A compound composed of a metal atom bonded to one or more oxygen atoms. | Metal Oxide |
| What is an example of a reaction where the mass of the products may seem greater than the mass of the reactants? | An example is when oxygen from the air reacts with a metal in an unsealed container to form solid metal oxide. |
| A container that is not completely sealed or airtight, allowing gases from the atmosphere to enter and exit freely. | Unsealed Container |
| Why does the measured mass of the reactants not include the mass of atmospheric oxygen in some reactions? | The mass of the reactants may not include atmospheric oxygen because it's floating about in the air and not directly measured. |
| An apparent increase in mass observed in some reactions, caused by the inclusion of atmospheric gases in the products. | Mass Increase |
| What causes the mass of the container and its contents to increase in reactions involving atmospheric gases? | The inclusion of atmospheric oxygen in the metal oxide product causes the mass of the container and its contents to increase. |
| The formation of gaseous products during a chemical reaction, often resulting in an apparent decrease in mass. | Gas Production |
| What can cause the mass of the products to appear less than the mass of the reactants in some reactions? | The formation of one or more gaseous products during the reaction can cause the mass of the products to appear less than the mass of the reactants. |
| The breakdown of a compound into simpler substances due to the application of heat, often resulting in the formation of gaseous products. | Thermal Decomposition |
| What is an example of a reaction where the mass of the products may seem less than the mass of the reactants? | An example is when a metal carbonate thermally decomposes in an unsealed container to form a metal oxide and carbon dioxide gas. |
| A compound composed of a metal atom bonded to one or more oxygen atoms in a solid state. | Solid Metal Oxide |
| Why does the measured mass of the products not include the mass of carbon dioxide gas in some reactions? | The mass of the products may not include the mass of carbon dioxide gas because it escapes into the atmosphere and is not directly measured. |
| A decrease in apparent mass observed in some reactions, caused by the production of gaseous products. | Apparent Mass Decrease |
| What causes the mass of the container and its contents to decrease in reactions involving gas production? | The escape of carbon dioxide gas into the atmosphere causes the apparent mass of the container and its contents to decrease. |
| The masses of reactants and products in an equation can be calculated using their relative formula masses. | Mass Calculation |
| This is a balanced equation for the reaction of methane (CH4) and oxygen to form water and carbon dioxide. | Water and Carbon Dioxide Balanced Equation |
| If, for example, you know that 56 g of methane reacted, you can calculate the mass of water (H2O) that will be formed. | Mass of Water Formed |
| Write down the mass of the methane and leave a space for the mass of the water to be calculated. | Methane Mass Calculation - Step 1 |
| Calculate the relative formula mass of methane and water. | Relative Formula Mass Calculation - Step 2 |
| Determine the number of moles of methane by dividing its mass by its relative formula mass. | Methane Moles Calculation - Step 3 |
| In the balanced equation, 1 methane molecule reacts with oxygen to form 2 water molecules (the ratio of methane to water is 1 : 2). | Stoichiometric Ratio - Step 4 |
| Double the number of moles of methane to find the number of moles of water formed. | Water Moles Calculation - Step 5 |
| Multiply the number of moles of water by the relative formula mass of water to find the mass of water formed: 126 g. | Water Mass Calculation - Step 6 |
| A measure of the amount of a substance (solute) dissolved in a certain volume of solution. | Concentration |
| What is concentration? | Concentration is the measure of the amount of a substance dissolved in a certain volume of solution. |
| The substance that is dissolved in a solvent to form a solution. | Solute |
| What is the dissolved substance in a solution called? | The dissolved substance in a solution is called the solute. |
| A unit of concentration representing the number of grams of solute dissolved in one cubic decimeter (dm3) of solution. | Grams per dm3 (g/dm3) |
| What is the equivalent volume of 1 dm3 in other commonly used units? | 1 dm3 is equivalent to 1000 cm3 or 1 liter. |
| A mathematical expression used to calculate the concentration of a solution, typically represented as the amount of solute dissolved in a given volume of solvent. | Concentration Formula |
| How would you calculate the concentration of a solution containing 50 g of potassium chloride dissolved in 0.5 dm3? | You would use the concentration formula to calculate the concentration of the solution. |
| A rearranged form of the concentration formula used to calculate the mass of solute given the volume and concentration of a solution. | Mass Calculation Formula |
| How would you work out the mass of sodium chloride in 12 dm3 of a 5 g/dm3 solution? | You would rearrange the concentration formula to calculate the mass of the solute. |
| A condition where the concentration of a solution is relatively high due to a large amount of solute dissolved in a small volume of solvent. | High Concentration |
| What factors contribute to a high concentration of a solution? | A high concentration occurs when there is a large mass of solute dissolved in a small volume of solvent. |
| A condition where the concentration of a solution is relatively low due to a small amount of solute dissolved in a large volume of solvent. | Low Concentration |
| What factors contribute to a low concentration of a solution? | A low concentration occurs when there is a small mass of solute dissolved in a large volume of solvent. |
