Unit 2-lesson 4 Chemical Properties

Question 0

What is reactivity?

Answer 0

Reactivity is how easily one substance reacts with another substance

Example: copper, silver, and gold are examples of substances that do not react with water. Cesium and sodium are two substances that react strongly with water.

Question 1

What is the chemical property?

Answer 1

The ability of the substance to combine with or change into one or more new substances

Question 2

What is flammability?

Answer 2

Flammability is a chemical property of a substance that describes its ability to catch on fire.

Hydrogen and methane are examples of flammable substances. Rocks and sand are nonflammable.

Question 3

Why is it important to know the chemical properties of a substance?

Answer 3

We choose to use substances based upon their chemical properties. Gasoline is used in cars because it burns easily making the car go. Phosphorus is used at the end of the match because it ignites easily. Gold and silver are used for jewelry because they do not rust. Helium is used in blimps because it is not as flammable as hydrogen, making it safer.

Question 4

Is this a physical or chemical property? A substance rusts when it is exposed to water.

Answer 4

This is an example of a chemical property because a new substance is formed.

Question 5

Why do many cleaning products have safety instructions on them?

Answer 5

It is important to know the chemical properties of the substance to keep people safe from harmful vapors, flammability, combustibility, and the reactivity of substances.

Question 6

What is an acid?

Answer 6

An acid can turn blue litmus paper pink or red. An acid is a chemical property because it can react with other substances.

Acids release hydrogen ions (H+) in solution.

An acid is a pH of below 7 on the pH scale.

Question 7

What to do acids react with?

Answer 7

Acids can react with metals, limestone, and some acids are strong enough to even burn your skin.

Question 8

What is a base?

Answer 8

A base can turn red litmus paper blue. They turn red cabbage juice to green. A base is a chemical property because a base reacts with other substances.

Bases release hydroxide ions (OH-) in a solution.

A base in a pH greater than 7.

Question 9

How does a base feel?

Answer 9

A base can feel slippery to the touch because the base reacts to the proteins in your tissues on your fingertips.

An example of a base are soaps.

Question 10

What are bases and acids used for?

Answer 10

Many acids and bases are used in cleaning products.

Like acids strong bases can damage your tissues.

Question 11

What is the pH scale?

Answer 11

The pH scale measures the strength of acids and bases. It runs from 0 to 14. Substances below 7are acids. Substances greater than 7 are bases. Substances that are 7 are neutral.

Question 12

What are indicators?

Answer 12

Indicators are materials that change the color in the presence of acids or bases. Some indicators, litmus paper, react to either an acid or base. Other such as pH paper, Flavin in red cabbage juice, reacts to both acids and bases.

Question 13

What is neutralization?

Answer 13

Neutralization is the process by which acids and bases react to each other to form water and substances called salts. The pH of a substance that is neutral is 7.

Sodium hydroxide and hydrochloric acid form table salt.

Question 14

Which substances on the pH scale would be most dangerous to handle?

Answer 14

Substances that would be most dangerous to handle, would be substances that are the most acidic 1-2 or most basic 12-14 on the pH scale.

A substance that is neutral would be safest to handle.

Question 15

How does an acid taste?

Answer 15

Acids usually taste sour. Citric acid in lemons makes things taste sour. Vinegar is also sour because it contains acetic acid.

Question 16

How does a base taste?

Answer 16

A base usually tastes bitter. Baking soda is an example of a base.

Question 17

Is tasting a substance a safe way to determine if it is an acid or a base?

Answer 17

No. Tasting a substance is a not a safe way to determine if it is an acid or a base and it could be very dangerous. This is why people use litmus paper, pH paper, or red cabbage juice to determine if things are acids or bases.

Question 18

If you know that a lemon has a pH of 2 and you taste another fruit juice that taste sour, what would you predict the pH of that used to be?

Answer 18

You would probably predict that the pH of another fruit juice that taste sour would also be a 2. You would also know that the fruit was an acid.

Question 19

Why do you think acids and bases are used in many cleaning products?

Answer 19

Acids and bases breakdown and dissolve many substances. This is very helpful when cleaning things. The bottom of a copper pot maybe cleaned with ketchup because it contains vinegar which breaks down residue that may buildup.

Question 20

How do chemical and physical properties compare?

Answer 20

All matter can be described using both physical and chemical properties.

Example: Copper is a solid, a good conductor, and is reddish-brown in color. These are all physical properties of copper.

When copper is in contact with air for a long time, it reacts. Rainwater and carbon dioxide then reacted with the new substance and a green substance is formed. This substance protects the copper underneath. Example the Statue of Liberty. This is an obvious chemical property of copper.