Chemical Reactions 7.1.2

​Chemical Reaction 7.1.2
Notebook Page 132

​Take some NOTES!

​What's the difference between the two images?
How are they alike? How are they different?

​Why did the cookies change as they baked?

​Matter does not always stay the same. Like energy, matter can change. In this lesson, you will learn about ways that matter changes. You will learn about:

• physical and chemical changes;

• chemical reactions; and

• signs of a chemical change.

Match

Match the words to their definitions

• chemical bond

• chemical reaction

• atom

• physical change

• molecule

an attraction between atoms

a process that leads to the transformation of one set of chemical substances to another

the basic unit of a chemical element

a change that affects one or more physical properties of a substance

two or more atoms bonded together

• an attraction between atoms

• a process that leads to the transformation of one set of chemical substances to another

• the basic unit of a chemical element

• a change that affects one or more physical properties of a substance

• two or more atoms bonded together

​Physical and Chemical Changes

Matter can change in many ways. Two categories that chemists use to classify changes in matter are:

• physical change

• chemical change

Draw

Circle the correct answer.

Remember: One helpful way to identify a physical change is to think about if you can easily reverse the change.

​Chemical Changes

A chemical change is a change in matter that creates a new substance. A chemical change causes one or more new chemicals to form.

The properties of a substance before a chemical change are different from the properties after a chemical change. Think about sodium chloride, which is table salt.

• Sodium is a soft metal that explodes when it contacts water.

• Chlorine is a poisonous gas.

• Sodium chloride is a seasoning added to food.

The properties of sodium chloride are very different from the properties of the individual elements that form the chemical.

Categorize

Options (16)

lava har

melting ice

boiling water

dissolving sugar

breaking glass

chopping wood

crumpling paper

mixing sand and salt

rusting iron

burning wood

baking a cake

souring milk

digestion of food

fermentation of grapes

exploding fireworks

photosynthesis

Classify each change as either physical or chemical.

physical change

chemical change

​Any guesses on what this is showing you or what's happening?

​Photosynthesis

​Chemical changes are caused by chemical reactions. A chemical reaction is a process in which one chemical changes into another chemical. Recall that a chemical is a substance that always has the same composition. Think about what happens during photosynthesis.

• Before photosynthesis, plant cells contain carbon dioxide and water.

• After photosynthesis, plant cells contain glucose and oxygen.

• ​As you watch the video, make observations.
  What changes do you see?
  Are there some common changes?
  Do some of the experiments have similarities?
  How can you tell these are chemical reactions?

Multiple Choice

There are several ways to tell that a chemical change has occurred. One clue is the production of gas. Which of the following tells you that a reaction produced gas?

• Bubbles forming or a noticeable gas release.
• Formation of a solid precipitate
• Temperature increase without bubbles
• Color change without gas release

​Recall that the CER method is a way to make a scientific argument. A scientific argument consists of three parts.

1. A claim that states the main idea of the scientific argument. A claim can be a conclusion or an answer to a scientific question.

2. Evidence that is either qualitative or quantitative data. The evidence provides data that supports the claim.

3. Reasoning that connects the evidence to the claim. Reasoning explains how the evidence supports the claim. Reasoning can also explain how the things you learned in a lesson support a claim.

​The elephant toothpaste demonstration is an example of a chemical reaction.

1. View the GIF and look for signs of a chemical reaction. Record those observations as evidence that supports the claim.

​Google: World's Tallest Elephant Toothpaste Video

​https://youtu.be/e09xig209cQ?si=aKRT9hfXKBByV_jf

​Video time! Edio page 3

Classifying Matter