In a chemical reaction, new products are formed from

the reactants. How can you tell this has happened?

There are a few clues you can look out for that might

mean a reaction has taken place.

In some cases, a gas is given off, or heat is produced.

Sometimes you can see a color change or you can

check a chance in the pH using an indicator.

Some reactions between two liquid reactants can

produce a solid precipitate.

Today, we will watch videos about different reactions taking place and we will identify how we can tell a reaction is happening.

In each point you will watch the video of a reaction, you must click on the image to go to the link of the video:

1. Watch the following video (you will only need to watch some specific parts)

a) Write the word equation for this reaction

b) Write the chemical equation

c) At the end of the reaction, what was the

clue or change you could easily identify to

know that a reaction took place?

2. Watch the video. You can use the information from last the class about reactions with acids to have the formulas.

a) Write the 2 chemical equations (One for Mg,

one for Zn) (They are 2 different rxns). This is the

first equation, the second one is similar, but instead

of Mg is with Zn:

Mg + HCl MgCl + H2

b) Write the word equations (HCl = Hydrochloric acid)

c) How can we know that a reaction has

taken place?

3. Watch the video about Potassium and water

a) Write 3 changes that happen during the reaction

b) Write the word and chemical formulas

c) Investigate why is Potassium called an alkali

metal, what does this mean?

4. Sodium hydroxide and hydrochloric acid react to produce sodium chloride and water. Watch the video and answer the questions:

a) Write the chemical equation

b) What happens to the sodium hydroxide

when he adds the phenolphthalein?

c) What happens when he mixes both

reactants?

d) Investigate what is the name of a reaction

in which an alkali neutralizes an acid?

5. Silver nitrate and calcium chloride react to form silver chloride and calcium nitrate. Watch the video and answer: (the rxn starts in minute 2:25)

a) Write the chemical equation (no video

needed for this)

b) What is the change that allows you

to know that a reaction took place?

6. Using what you learnt during the previous classes, create a word search game (sopa de letras) with clues to find the following terms:

Element Products

Chemical Precipitate

Physical Rusting

Mixture Solution

Reactants Reaction

Compound Combustion

Balance is an important part of life. We try to find

balance between work and rest, responsibilities

and free time, challenges and fun. In chemistry,

balance is just as important. During a chemical

reaction, atoms cannot simply disappear or appear

out of nowhere—they must be rearranged.

This means that the number of each type of atom must be the same before and after the reaction. Today, we are going to discover how to bring this balance to chemical equations and become Chemical Equalizers!

Today's goal is:

So, before we start, check out this equation:

H₂ + O₂ → H₂O

There is something wrong with it, what is it?

To learn more about how to balance equations, first, write the main ideas from this presentation:

1. Say if the following chemical equations are balanced or not, show your working by stating how many atoms of each element there are in each side:

2. Visit this PHET Website, click on INTRO and practice balancing equations by changing the coefficients of the molecules. Do this by balancing the equations of the 3 chemical processes shown in that website: Making Amonia, separating water and methane combustion. Then WRITE one of the equations and DRAW the molecules it represents.

3. Balance the following equations following the rules learned in class: