Limewater Reaction Investigation 9 Part 2 Day 2

Review What happened when air was pumped through the limewater? nothing What happened when exhaled breath was blown through the limewater? There was a change, the liquid turned cloudy What caused the change? Breath reacted with limewater to form a precipitate.

What could cause breath, which is also air, to react with limewater when air in the room would not? Breath is made of carbon dioxide Maybe CO 2 reacts with limewater

Atom Tiles Small replicas Use to figure out how atoms might go together in a particle of a substance. Work with partner. Calcium hydroxide – Ca(OH) 2 Limewater is Ca(OH) 2 dissolved in water. Use the atom tiles to make a model of a particle of Ca(OH) 2

Record the Representation Turn to Lab Manual page 89 Limewater Investigation B When you and your partner are satisfied with your model of calcium hydroxide, draw it in the first section of the sheet.

When a chemical reaction occurs, (write in notebook) The atoms of the starting substances rearrange to form new substances. Reactants are the starting substances Products are the new substances Work on question 2 with your partner Use your atom tiles to create atomic representations of the reactants. One compound is calcium hydroxide Ca(OH) 2

Now Reorganize the atom tiles to make representations of the products of the reactions. One of them is the white precipitate. – What white precipitate have we worked with? – What is left? – *Write down the chemical formula for the products.

Reactants One compound is calcium hydroxide Ca(OH) 2 *Write down the formula for the reactants The second reactant was in your breath. What waste gas do we breathe out? Carbon dioxide, CO 2 The white precipitate forms because it is insoluble in water. What white powder do you know that does not dissolve in water? Calcium Carbonate, CaCO 3

The reaction Volunteer to identify the reactants. Second volunteer to rearrange the atom representation to form products Write the correct representations in your notebooks

Chemical formulas and equations Chemists write reactions using chemical formulas, not atom models. Chemical formulas have the same information as atom representations These are the conventions for writing chemical equations.

Conventions for writing chemical equations (write in notebook) Reactants are written as chemical formulas on the left side of the equation. They are separated from each other with plus signs. Products are on the right side of the equation, separated with plus signs. An arrow pointing to the right is used in place of an equal sign. The arrow is read “yields” If a product is a gas, an arrow pointing up follows its chemical formula If a product appears as a precipitate, an arrow pointing down follows its chemical formula

An example (write in notebook) REA 1 +REA 2  PRO 1  + PRO 2  This equation tells us that reactant 1 plus reactant 2 yields product 1, a gas, and product 2, a precipitate. Write the equation for the calcium hydroxide reaction using chemical formulas in the space under question 3. Write the chemical names of the substances under the formulas.

Limewater Investigation B Complete the last 3 questions Turn in work.

Read How Do Atoms Rearrange? Complete LM page 91