Starter quiz
- What is a molecule?
- A single atom of an element.
- Two or more atoms chemically bonded together. ✓
- A mixture of different compounds.
- A type of chemical reaction.
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- In a chemical reaction, the substances formed are called ______.
- 'products' ✓
- Which of the following is a compound?
- O₂
- H₂O ✓
- N₂
- He
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- What happens to atoms during a chemical reaction?
- They disappear.
- They are created from nothing.
- They rearrange to form new substances. ✓
- They stay the same and do not change.
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- What is the chemical formula for carbon dioxide?
- CO
- CO₂ ✓
- C₂O
- C₂O₂
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- A chemical symbol ______ is a representation of a chemical reaction using the symbols of the elements involved.
- 'equation' ✓
Exit quiz
What does the arrow in a chemical equation represent?- equal to
- plus
- changes into ✓
- multiplies
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- Which of the following statements about the mass of reactants and products in a chemical reaction is correct?
- The mass of the reactants is greater than the mass of the products.
- The mass of the reactants is less than the mass of the products.
- The mass of the reactants is equal to the mass of the products. ✓
- The mass of the reactants can be greater or less than the mass of the products.
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- What is a word equation?
- A way of describing a reaction using symbols.
- A way of describing a reaction using chemical names of reactants and products. ✓
- A balanced symbol equation.
- A type of chemical formula.
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- Why must symbol equations be balanced?
- To change the identity of the reactants.
- To show that matter is created or destroyed.
- To correctly represent the conservation of mass. ✓
- To make the equation more complicated.
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- A ______ represents a substance using element symbols and the number/ratio of atoms of each element in the substance.
- 'chemical formula' ✓
- To balance a chemical equation, you need to change the ______ in front of the chemical formulas to ensure there are equal numbers of atoms of each element on both sides of the equation.
- 'coefficient' ✓
Worksheet
Presentation
Video
Lesson Details
Key learning points
- The mass of the products in a chemical reaction is the same as the mass of the reactants.
- Word equations are a simple way of describing chemical reactions.
- Chemical formulae represent the numbers of each type of atoms in a reactant or product.
- Chemical equations represent how the atoms in the reactants rearrange to form the products.
- The arrow in a chemical equation represents the words ‘changes into’.
Common misconception
Pupils get confused with what numbers can be changed, many of them try to change the subscript numbers in formulae to balance equations.
Use the layout modelled in the slides to go through the examples using the 'circled method' and tell pupils that when adding more of a substance they must add all elements in the substance, e.g. 2MgO = (MgO)(MgO).
Keywords
Chemical formula - represents a substance using element symbols and the number / ratio of atoms of each element in the substance.
Word equation - is a way of describing a reaction using the chemical names of the reactants and products.
Balanced symbol equation - describes a reaction using a symbol equation with coefficients, which ensure there are equal numbers of atoms of each element on both sides of the symbol equation.
Coefficient - is the number placed in front of a chemical formula to balance an equation; it multiplies all the atoms in the formula and shows the ratio of substances in a reaction.